QT4-4- 


y^zj/^*/- 


A 

HANDBOOK 


PHYSIOLOGICAL  LABORATORY, 


CONTAINING 

AN   EXPOSITION   OP  THE   FUNDAMENTAL  FACTS   OF  THE 

SCIENCE,  WITH  EXPLICIT  DIRECTIONS  FOR 

THEIR  DEMONSTRATION. 

HTSTOT  Or1  V'     PartB  l  and  1I-     By  B'  Klein>  m,d>  Assistant  Professor  in  the 
Pathological  Laboratory  of  the  Brown  Institute,  London. 

PHYSTOT  OPT"'  Part  r'  BL00D  CIRCULATION,  RESPIRATION  AND 
ANIMAL  HEAT.  By  J.  Burdox  Sanderson,  m.d.,  Pro- 
fessor of  Physiology,  University  College,  London. 

«  Part  II.     THE  FUNCTIONS  OF  THE  MUSCLES   AND 

NERVES.  By  Michael  Foster,  m.d.,  Prelector  of  Physi- 
ology, Trinity  College,  Cambridge;  Author  of  a  Text-boofc 
of  Physiology,  etc. 

ti  .    Part  III.    DIGESTION  AND  SECRETION.    By  T.  Lauder 

Bhunton,  m.d.,  Lecturer  on  Materia  Medica  and  Therapeu- 
tics, St.  Bartholomew's  Hospital,  etc. 


EDITED   BY 

J.   BURDON   SANDERSON,   M.D. 

WITH 

ONE  HUNDRED  AND  THIRTY-THREE  FULL-PAGE   PLATES, 

CONTAINING 

353  BEAUTIFULLY  EXECUTED  ILLUSTRATIONS. 
WITH  BEFEBENCEfi   \M>  EXPLANATIONS 


PHILADELPHIA: 
BLAKISTON,    SON    &   CO., 

No.  1012  Walm   i    Sti.-kjct. 
188  I. 


TO 

WILLIAM  SHARPET.  M.D.  LL.D.  F.R.S.  F.R.S.E. 

PROFESSOR  OF  AS  ATOMY  AND  PHYSOT.OGT  IX  CX1VERSITY  COLLEOE     LOXO   X.  ET 

Dear  Dr.  Sharpey, 

To  you,  who  have  been  these  many  years  the  friend 
of  physiologists  throughout  the  world,  and  who,  by  your 
original  work,  by  your  teaching,  by  your  generous  aid  and 
judicious  counsel,  have  been  the  mainstay  of  physiology  in 
England,  we  desire  to  dedicate  this  attempt  to  promote  the 
study  of  our  science. 

Accept  it  as  a  token  of  our  personal  regard,  as  well  as  of 
the  high  value  we  set  on  your  life-long  labors. 

Your  devoted  Friends, 

MICHAEL  FOSTER, 
J.  BURDON-SANDERSON, 
T.  LAUDER  BRUNTON, 
E.  KLEIN. 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 
Columbia  University  Libraries 


http://www.archive.org/details/handbookforphysiOOburd 


EDITOR'S  PREFACE. 

This  book  is  intended  for  beginners  in  physiological 
work.  It  is  a  book  of  methods,  not  a  compendium  of 
the  science  of  physiology,  and  consequently  claims  a  place 
rather  in  the  laboratory  than  in  the  study.  But  although 
designed  for  workers,  the  authors  believe  that  it  will  be 
found  not  the  less  useful  to  those  who  desire  to  inform 
themselves  by  reading  as  to  the  extent  to  which  the 
science  is  based  on  experiment,  and  as  to  the  nature  of 
the  experiments  which  chiefly  deserve  to  be  regarded  as 
fundamental. 

The  practical  purpose  of  the  book  has  been  strictly  kept 
in  view,  both  in  the  arrangement  and  in  the  selection  of 
the  subjects.  Many  subjects  are  entirely  omitted  which 
form  important  chapters  in  every  text-book.  They  have 
been  left  out  either  because  they  do  not  admit  of  experi- 
mental demonstration,  or  because  the  experiments  required 
are  of  too  difficult  or  complicated  a  character  to  be  either 
shown  to  a  class  or  performed  by  a  beginner. 

The  mode  of  arrangement  will  be  found  to  be  somewhat 
different  in  the  four  sections  into  which  the  work  is 
divided.  This  difference,  although  in  part  attributable  to 
difference  of  authorship,  is  mainly  due  to  the  peculiarities 
of  the  modes  of  demonstration  required  in  the  several  sub- 
jects. 

As  regards  the  physiology  of  nerve  and  muscle,  it  is 
sufficient  to  refer  the  reader  to  the  author's  introduction 
for  an  exposition  of  the  method  followed.  Iu  the  his- 
tological part  will  be  found  a  purely  objective  description 
of  anatomical  facts  and  methods.  Substituting  chemical 
for  anatomical,  the  same  tiling  might  be  said  of  the  chap- 
ters relating  to  tin-  chemical  functions.  Ilere,  where 
minuteness  of  description  is  essential,  great  pains  have 
been  taken  to  -jive  the  student  the  most  ample  details  as 


Vlll  l'l'.KF  ace. 


regards  materials  for  work,  instruments,  and  methods.  In 
the  chapter  on  the  blood,  the  same  object  has  been  kept 
in  view,  but  in  those  relating  to  the  mechanical  functions 

of  circulation  and  respiration,  where  either  man  or  the 
higher  animals  must  he  for  the  most  part  the  subjects  of 
observation,  and  where  consequently  the  conditions  of 
experiment  are  complicated  by  the  interference  of  the  ner- 
vous system  to  an  extent  which  it  is  often  difficult  to 
estimate,  it  has  been  found  impossible  to  avoid  entering 
somewhat  more  largely  into  theoretical  explanations. 

In  the  chapters  on  digestion  and  secretion,  and  in  the 
remainder  of  the  chemical  part,  those  experiments  or 
methods  which  arc  most  important  and  hist  suited  for 
demonstration  are  distinguished  by  two  asterisks  (**),  the 
less  important  by  a  single  asterisk  (*).  The  absence  of  an 
asterisk  at  the  beginning  of  a  paragraph  denotes  either 
that  the  experiment  is  unimportant  or  that  it  is  difhVult 
to  perform.  A  dagger  (f)  is  used,  to  draw  special  atten- 
tion to  a  test  or  procedure. 

I  have  to  record  Dr.  Brunton's  obligation  to  Dr.  Arthur 
Gamgee,  F.R.S.,  for  many  important  suggestions  in  the 
preparation  of  the  chapter  on  secretion.  Dr.  Brunton 
further  wishes  me  to  state  that,  although  he  has  recom- 
mended no  method  as  suitable  for  demonstration  which 
he  has  not  himself  tried,  he  has  freely  availed  himself  of 
the  well-known  works  of  Hoppe-Seyler,  Gorup-lU'sanez, 
and  Ivuhne,  both  in  the  arrangement  of  the  sections  and 
in  the  selection  of  experiments. 

It  has  been  judged  expedient  by  the  Publishers  to  sepa- 
rate the  illustrations  from  the  text.  In  this  way  full 
justice  has  been  done  to  the  engravings  of  the  Histologi- 
cal part,  which  have  been  executed  by  Mr.  Collings  from 
the  original  drawings  of  the  author. 

Most  of  the  illustrations  of  the  Physiological  part  are 
the  work  of  the  same  artist,  both  as  regards  drawing  and 
engraving.  Of  the  remainder,  several  have  been  borrowed 
(with  the  kind  permission  of  the  author)  from  Mr.  Sut- 
ton's work  on  Volumetrical  Analysis. 


CONTENTS. 


HISTOLOGY.— PART  I. 
CHAPTER  I. 

PAGE 

Blood  Corpuscles '.        .        .17 

CHAPTER  II. 
Epithelium  and  Endothelium 35 

CHAPTER  III. 
Connective  Tissues 4G 

CHAPTER  IV. 
Muscular  Tissue 65 

CHAPTER  V. 
TISSUES  of  TnE  Nervous  System 70 


HISTOLOGY— PART  II. 

CHAPTER  VI. 
Preparation  op  TnE  Compound  Tissues         ....    100 

CHAPTER  VII. 
Vascular  System 110 

CHAPTER  VIII. 
Lymphatic  System 123 

CHAPTER  IX. 
Organs  of  Respiration 133 


X  CONTENTS. 

CHAPTER  X. 

PA(iK 

Organs  of  Digestion 135 

CHAPTER  XI. 

Skin,  Cutaneous  Glands,  and  Genito-1  binary  Apparatus    141 

CHAPTER  XII. 
Organs  of  Special  Sense 150 

CHAPTER  XIII. 
Embryology 158 

CHAPTER  XIV. 
Appendix. — Study  of  Inflamed  Tissues         ....     IG9 


PHYSIOLOGY.— PART  I. 

Blood,  Circulation,  Respiration,  and  Animal  Heat. 

CHAPTER  XV. 
The  Blood 175 

CHAPTER  XVI. 
The  Circulation  of  the  Blood .2 17 

CHAPTER  XVII. 
Respiration 298 

CHAPTER  XVIII. 
Animal  Heat S36 


PHYSIOLOGY.— PART  II. 
Functions  of  Muscle  and  Nerve. 

CHAPTER  XIX. 
General  Directions 350 

CHAPTER  XX. 
General  Properties  of  Muscle  at  Rest       ....     360 


CONTENTS.  XI 

CHAPTER  XXI. 

PAGE 

Preliminary  Observations  on  the  Stimulation  op  Nerve 
and  Moscle 364 

CHAPTER  XXII. 
Phenomena  and  Laws  op  Muscular  Contraction    .        .        .     365 

CHAPTER  XXIII. 
The  "Wave  of  Muscular  Contraction 369 

CHAPTER  XXIV. 
Tetanus 371 

CHAPTER  XXV. 
Electric  Currents  of  Muscles 370 

CHAPTER  XXVI. 

Electric  Currents  op  Nerves 381 

CHAPTER  XXVII. 
Electrotonus 382 

CHAPTER  XXVIII. 
Stimulation  of  Nerves 383 

CHAPTER  XXIX. 
Phenomena  accompanying  a  Nervous  Impulse        .        .        .    393 

CHAPTER  XXX. 
Various  Forms  op  Stimulation  op  Muscle  and  Nerve    .      .    395 

CHAPTER  XXXI. 
Dbar]  Poisoning  and  Independent  Muscular  Irritability.    398 

CHAPTER  XXXII. 
The  Functions  OF  the  Roots  ok  Spinal  Nerves      .         .         .     402 

CHAPTER  XXXIII. 
Reflex  Actions 406 

CHAPTEB  XXXIV. 
ome  Functions  of  Cebtaih  Parts  of  the  Ekcephaloh  .    418 


x'li  CONTENTS. 

PHYSIOLOGY— PART  III. 
Digestion  and  Secretion. 

CHAPTER  XXXV. 

TA'iP. 

Albuminous  Compounds 1-'1 


CHAPTER  XXXVI. 
Chemistry  of  the  Tissues  .... 


44! 


CHAPTER  XXXVII. 
Digestion **'" 

CHAPTER  XXXVIII. 
The  Secretions '-'' 

CHAPTER  XXXIX. 
Appendix.— Notes  on  Manipulation 561 


HISTOLOGY. 

By  Dr.  E.  KLEIN. 
PART  I.-PREPARATION  OF  THE  ELEMENTARY  TISSUES. 


CHAPTER  I 

BLOOD  CORPUSCLES. 


In  the  microscopical  examination  of  the  blood,  we  have  to 
do  only  with  the  study  of  the  formed  elements,  namely,  the 
colorless  corpuscles  and  blood  disks. 

Colorless  Blood  Corpuscles. — The  colorless  corpuscles 
are  elementary  organisms  which  are  endowed  with  the  power  of 
spontaneous  motion.  This  power  belongs  to  them  in  virtue  of 
the  material  of  which  their  bodies  are  composed.  This  mate- 
rial is  protoplasm.  Their  motion  is  of  two  kinds;  it  consists  of 
change  of  form  and  change  of  place.  The  latter  results  from 
the  former.  As  movements  of  this  kind  are  seen  in  greatest 
perfection  in  rhizopods  and  amoebae,  they  are  called  amoeboid. 

Amoeboid  Movements  of  Colorless  Corpuscles. — 
Very  active  movements  are  seen  in  the  colorless  blood  corpus- 
cles of  the  newt.  The  cells  are  large  and  easy  of  observation. 
It  is  of  the  first  importance,  in  beginning  our  study  of  them, 
that  they  should  be  placed  under  conditions  which,  if  not  iden- 
tical with,  are  not  materially  different  from,  those  under  which 
they  actually  exist.     The  simplest  method  is  the  following: — 

Take  a  clean  glass  slide  and  an  absolutely  clean  cover-glass, 
which,  as  we  must  use  high  powers  (that  is,  objectives  of  which 
the  focal  distance  is  short),  must  be  thin.  Take  the  newt  out 
of  the  water,  dry  the  tail,  cut  off  its  end.  If  no  blood  comes, 
squeeze  the  organ  from  the  root  towards  the  tip  until  a  drop  is 
obtained.  One  of  two  methods  may  now  be  used:  1st,  let  the 
blood  drop  upon  the  middle  of  the  glass  slide,  and  place  the 
cover-glass  on  it  in  such  a  way  that  one  edge  rests  on  its  sur- 
face, while  the  opposite  edge  is  supported  by  the  finger  or  for- 
ceps. Then  let  the  glass  gradually  down  upon  the  drop.  Or, 
2 


18  BLOOD   CORPUSCLI  ~. 

2dly,  collect  the  blood  on  the  cover-glass  by  bringing  it  into 
contact  with  the  drop,  then  place  it  on  the  slide  with  its  clean 
surface  upwards.  By  following  either  of  these  methods, 
the  introduction  of  air-bubbles  will  be  avoided,  which  would 
otherwise  be  a  source  of  difficulty  to  the  beginner.  The  drop 
should  be  neither  too  small  nor  too  large.  The  following  in- 
conveniences arise  from  its  being  too  large:  1.  The  thin  cover- 
glass  does  not  lie  steadily  in  its  place,  but  floats  on  the  drop 
in  such  a  way  that,  by  the  slightest  movement  of  the  table, 
currents  are  produced  in  the  liquid  which  render  observation 
difficult  or  impossible.  2.  If  it  is  desired  to  keep  the  preparation 
for  a  length  of  time  under  observation,  it  is  necessary  to  adopt 
some  means  to  prevent  the  liquid  from  evaporating  ;  for,  if  this 
is  not  done,  it  gradually  dries  from  the  edges,  and  soon  be- 
comes unfit  for  the  observation  of  amoeboid  movements,  we 
therefore  inclose  the  preparation  in  oil,  as  will  be  immediately 
described,  and  experience  shows  that,  by  so  doing,  the  move- 
ments may  be  watched  for  twelve  hours  or  more  continuously 
— a  time  which  is  sufficient  for  a  complete  study  of  the  phe- 
nomena in  question.  This,  however,  cannot  be  done  unless 
the  drop  is  very  small.  3.  If  high  powers  are  used,  the  front 
glass  of  the  objective  comes  into  contact  with  the  cover-glass, 
and  produces  currents  due  to  pressure. 

If,  on  the  other  hand,  the  drop  is  too  small,  the  elements 
are  pressed  upon  by  the  cover-glass,  and  thereby  subjected  to 
unnatural  conditions.  No  definite  rule  can  be  given  as  re- 
gards the  size  of  the  drop,  which  must  of  course  vary  with 
that  of  the  cover-glass. 

The  mode  of  surrounding  a  preparation  of  blood  with  oil  is 
as  follows  :  Take  a  drop  with  a  glass  rod  or  camel-hair  pencil, 
and  let  it  fall  at  the  very  edge  of  the  cover-glass  in  such  a 
way  that,  although  most  of  it  is  on  the  surface  of  the  slide,  it 
covers  a  little  of  the  cover-glass  also.  Then  incline  the  glass 
slide  slightly,  and  with  the  rod  lead  the  oil  from  the  drop 
along  the  edge  of  the  cover-glass,  taking  care  not  to  press 
upon  the  latter.  If  one  drop  of  oil  is  insufficient,  of  course 
another  must  be  added.  Take  great  care  to  avoid  smearing 
the  cover  glass  too  far;  for  by  so  doing,  the  space  available 
for  observation  may  become  inconveniently  limited. 

Having  thus  obtained  a  preparation  of  blood  entirely  pro- 
tected from  evaporation,  we  are  ready  to  begin  our  study  of 
the  colorless  corpuscles. 

Varieties  of  Colorless  Corpuscles. — As  soon  as  we 
have  brought  a  field  containing  blood  into  focus,  we  see,  in 
addition  to  a  multitude  of  colored  blood  disks,  to  which  we  at 
present  pay  no  attention,  a  greater  or  less  number  of  color- 
less corpuscles,  which  themselves  differ  from  one  another  both 
in  size  and    aspect,  and    in   their   property  of  spontaneous 


BY   DR.    KLEIN.  19 

movement.     Three   forms   may   be    distinguished,    which   we 
will  examine  in  succession  : — 

1.  Common  Large  Colorless  Corpuscles. — Supposing 
that  a  few  moments  have  elapsed  since  the  preparation  was 
made,  some  of  these  pale  corpuscles  are  sure  to  be  seen  float- 
ing hither  and  thither  in  the  liquid  with  a  rolling  movement. 
The}r  are  much  more  numerous  than  the  other  forms. 

Fix  the  attention  on  one  of  these  bodies,  and  observe,  first, 
that  it  is  so  transparent  that,  as  it  rolls  over  and  6ver,  a  single 
granule  embedded  in  its  substance  may  be  kept  constantly  in 
view.  Continuing  the  observation,  notice  that  the  surface  of 
the  corpuscle,  at  first  smooth,  gradually  becomes  uneven. 
The  cause  of  the  unevenness  is  this.  The  surface  is  beset 
with  a  greater  or  less  number  of  filamentous  appendages, 
varying  in  lengtL^  and  distributed  over  the  surface  with 
variable  uniformity.  These  seem  to  consist  of  the  same 
material  as  the  body  of  the  corpuscle.  When  they  are  short 
the}'  may  be  compared  to  prickles,  when  longer  they  are  often 
bent  at  the  point.  Sometimes  we  see  one  of  the  processes 
lengthen  itself,  while  another  disappears;  sometimes  a  whole 
group  of  processes  push  out  on  one  side,  while  others  are  re- 
tracted on  the  opposite  side.  Occasionally,  from  the  small- 
ness  and  great  number  of  the  processes,  it  is  scarcely  possible 
to  be  sure  as  to  the  changes  which  occur.  Here  is  a  corpuscle 
which  appears  to  be  graduall}'  enlarging.  Let  us  follow  the 
changes  it  will  undergo.  Already  it  covers  a  space  three  or 
four  times  as  great  as  before.  Simultaneous!}'  with  this  in- 
crease of  size,  its  form  becomes  irregular,  and  (as  may  be 
ascertained  by  the  fine-adjustment  screw)  its  vertical  measure- 
ment is  diminished,  so  that  it  now  constitutes  a  thin  layer 
limited  by  a  distinct  contour.  Soon,  however,  the  circumfer- 
ence thins  out  in  certain  directions,  so  that  the  edge  can  no 
longer  be  discerned  ;  the  only  evidence  of  its  existence  in  these 
attenuated  parts  being  that  the  field  appears  to  be  covered 
with  a  granulous  film. 

In  the  layer  of  protoplasm  we  have  now  before  us,  some 
parts  are  hyaline,  or  contain  at  most  a  few  minute  granules. 
In  others,  you  will  notice,  there  are  clear  spots  with  well-de- 
fined contours,  which  differ  indefinitely  in  size,  and  have  no 
definite  arrangement.  Many  of  them  are  so  clear  that  they 
look  like  perforations.  It  is  characteristic  of  them  that  they 
are  undergoing  change,  both  as  regards  their  relative  position 
and  relative  distinctness,  some  coming  into  view  while  others 
are  fading.  These  we  call  vacuoles.  They  are  believed  to  be 
cavities  filled  with  liquid,  the  origin  of  which  is  due  to  the 
fonstant  commotion  of  the  protoplasmic  mass.  If  this  be  so, 
it  is  easy  to  understand  why  it  is  that  they  appear  and  dis- 
appear so  rapidly.     We  next  observe  that  at  some  part  of  the 


20  BLOOD   CORPUSCLES. 

corpuscle  (often,  but  not  always,  towards  the  centre)  one  or 
more  bodies  may  be  distinguished  of  roundish,  ovoid,  or  irre- 
gular form,  and  tolerably  distinct  contour,  somewhat  less  re- 
fractive than  the  surrounding  protoplasm,  and  containing  one 
or  more  granules.  These  bodies  are  commonly  close  together, 
and  arc  called  nuclei.  The  nuclei  are  usually  invisible  so  long 
as  the  colorless  blood  corpuscle  is  spheroidal  ;  when  it  spreads 
out  into  a  layer,  they  can  be  distinguished.  But  they  can  also 
be  observed  when  the  lamina  draws  itself  together  into  an  irre- 
gular clump  ;  and  it  may  be  then  seen  that  they  are  subject  to 
continual  change,  both  as  regards  form  and  relative  position. 

We  now  leave  the  corpuscle  we  have  been  hitherto  studying 
and  observe  another,  which  is  roundish,  and  exhibits  a  very 
few  delicate  processes.  At  present  we  see  no  nuclei.  After  a 
time  we  notice  that  one  of  the  processes  suddenly  becomes 
longer  and  thicker,  so  that  the  corpuscle'is  now  club-shaped, 
consisting  of  a  tapering  stalk  ending  in  a  knob.  The  stalk 
incloses  an  oblong,  compressed  nucleus,  and  the  knob  two 
such  nuclei  close  together,  the  surfaces  of  both  being  shaggy, 
with  minute  processes.  We  have  not  long  to  wait  until  the 
body  loses  this  form.  A  new  process,  towards  which  the  two 
nuclei  tend,  shoots  out  from  the  knob,  at  right  angles  to  the 
stalk.  The  knob  becomes  smaller  in  proportion  to  the  growth 
of  the  process,  while  the  two  nuclei  gradually  approach  its  ex- 
tremity. The  next  change  is,  that  each  process  lengthens  out 
in  the  direction  of  its  axis  into  a  filament,  the  two  together 
being  of  such  a  length  as  to  stretch  over  the  whole  field. 
These  filaments  spring  from  a  small  clump  of  granular  proto- 
plasm— the  original  knob  above  mentioned.  Each  filament 
swells  out  at  its  end  into  a  little  mass,  which,  in  the  one  case, 
contains  a  single  nucleus,  in  the  others,  two  nuclei.  Continu- 
ing our  observation,  we  notice  that  the  clump  at  the  junction 
of  the  two  filaments  disappears,  while  the  other  masses,  which 
are  now  united  \>y  a  straight  thread  of  nearly  equal  thickness 
throughout,  get  larger,  and  send  out  new  processes.  The 
larger  mass  now  creeps  nearer  the  edge  of  the  field  ;  the 
smaller  is  drawn  after  it,  but  moves  more  slowly,  so  that  the 
hyaline  thread  which  connects  them  gets  thinner  and  longer. 
But  while  we  are  watching  it,  the  large  mass  undergoes 
changes  which  are  a  repetition  of  what  we  before  observed  in 
the  original  clump.  A  process  shoots  out  from  it  at  right 
angles  to  the  direction  of  the  thread :  into  this  process  one  of 
the  nuclei  finds  its  way;  it  then  stretches  out  into  a  filament, 
wdiich  is  swollen  at  its  extremity  into  a  protoplasmic  envelope 
for  the  nucleus.  Still  later,  we  find  that  the  filaments  become 
thicker  and  shorter;  that  the  clumps  between  which  they 
stretch,  again  approach  one  another,  until,  in  their  confluence, 
the  original  form  reappears.     A  similar  series  of  changes  may 


BY    DR.    KLEIN.  21 

be   witnessed   in    any   corpuscle   of  the  kind   we  have  been 
studying. 

2.  Granular  Corpuscles. — Of  the  three  kinds  of  pale  cor- 
puscles which,  as  before  stated,  are  to  be  observed  in  the  blood 
of  the  newt,  we  have  now  to  consider  the  granular  cells.  These 
are  larger,  but  much  less  numerous  than  the  others,  and  are 
distinguished  by  the  large  dark  granules  they  contain.  To 
observe  them  we  must  make  a  fresh  preparation,  for  they  un- 
dergo changes  of  form  much  more  rapidly  than  the  others. 
The  granular  corpuscle  is  at  first  spheroidal.  Very  soon  its 
surface  exhibits  round  and  entirely  hyaline  prominences,  into 
which,  however,  granules  appear  shortly  to  find  their  way. 
So  long  as  the  corpuscle  presents  this  appearance,  the  only 
changes  of  form  observable  consist  in  heaving  movements  of  the 
prominences.  Eventualby,  one  of  these  suddenly  shoots  out 
into  a  prong-like  process,  into  which  the  granular  mass  of  the 
original  cell  flows.  Soon  the  corpuscle  throws  out  a  second 
similar  process,  into  which  the  mass  again  gathers  itself,  and 
in  this  way  advances  across  the  field,  with  more  or  less  ra- 
pidity. After  this  has  gone  on  for  a  certain  time  the  move- 
ments change  their  type  :  the  corpuscle  lengthens  itself  out 
into  a  thread,  in  which  the  movement  of  the  protoplasm  is 
rendered  visible  by  that  of  the  dark  granules  which  it  contains. 
The  thread  swells  out  at  the  end  into  a  little  mass,  from  and 
towards  which  alternately  the  rolling  motion  of  the  granules 
is  seen  to  be  directed.  Often  a  granular  corpuscle  may  be  ob- 
served to  creep  about  among  groups  of  colored  blood-disks, 
stretching  out  its  process  with  the  terminal  knob,  as  if  this  were 
a  feeler.  In  other  cases  we  may  witness  the  whole  series  of 
changes  described  in  the  preceding  paragraph  as  occurring  in 
the  ordinary  form  of  colorless  blood  corpuscle ;  the  main 
difference  being  that  the  transformations  are  accomplished 
within  shorter  periods.  Finally,  it  ma}'  be  noticed  that  in 
granular  cells,  even  when  they  are  spheroidal,  the  nuclei  often 
show  themselves  as  ovoid  spaces  free  from  granules.  They 
are,  however,  much  more  readily  distinguished  after  the  cell 
has  undergone  changes  of  form. 

3.  Colorless  Corpuscles  of  the  third  form. — In  addi- 
tion to  the  common  colorless  corpuscles  and  the  granular  cells 
we  have  just  had  under  observation,  we  notice  a  considerable 
number  of  colorless  elements  of  a  different  character.  These 
are  of  three  kinds  :  (a)  Small,  well-defined  bodies,  resembling 
nuclei,  which  retain  only  for  a  very  short  time  the  spheroidal 
form  which  they  had  at  first ;  (b)  larger  corpuscles,  consisting 
of  finely  granular  protoplasm,  with  jagged  outline,  containing 
three  or  four  distinct  nuclei,  which  may  be  either  roundish,  or 
flattened  against  each  other,  exhibit  a  double  contour,  and 
contain  a  few  fine  nucleoli  which  arc  relatively  of  a  large  size, 


22  BLOOD    CORPUSCLES. 

so  ranch  so,  that  they  often  appear  to  be  surrounded  by  a 
narrow  zone  of  protoplasm  ;  (<■)  large  masses  of  finely  granular 
protoplasm,  which  commonly  are  of  irregular  form,  and  in- 
close bodies  similar  to  the  nuclei  above  described,  varying  in 
number  from  five  to  twenty  in  each  mass.1 

Methods  of  Warming  a  Preparation. — As  in  our  fur- 
ther study  of  the  blood  corpuscles  it  will  be  necessary  to  em- 
ploy artificially  increased  temperatures,  we  proceed  to  describe 
the  methods  employed  for  applying  heat  to  preparations  whilst 
under  microscopic  observation.  These  methods  are  of  two 
kinds.  The  first  is  used  when  we  wish  to  subject  the  prepa- 
ration for  an  indefinite  period  to  an  increased  temperature,  to 
which  it  has  been  gradually  raised  ;  the  second  when  we  wish 
to  warm  it  suddenly,  but  for  a  very  short  period.  To  accom- 
plish the  first  of  these  objects,  a  very  simple  contrivance,  shown 
in  Fig.  1,  may  be  used.  Take  a  cover-glass,  and  spread  all 
round  the  edge  of  its  upper  surface  a  thin  layer  of  oil  ;  then 
take  another  cover-glass  of  the  same  size  as  the  first,  place 
on  its  centre  the  drop  of  the  blood  to  be  examined,  and  allow 
it  to  fall  on  the  glass  previously  prepared,  edge  to  edge,  with 
the  blood  drop  downwards.  The  drop  will  then  occupy  the 
space  between  the  two,  inclosed  by  the  layer  of  oil  in  such  a 
manner  that  it  may  be  examined  under  high  powers.  The 
preparation  may  then  be  readily  lifted  with  the  aid  of  a  lancet- 
shaped  knife,  and  placed  on  the  orifice  of  the  copper  plate  (e). 
The  copper  rod  (g)  is  then  gently  warmed  by  means  of  a  spirit- 
lamp,  a  little  cacao  butter  (or  some  other  fat,  the  fusing  point 
of  which  nearly  corresponds  to  the  desired  temperature)  having 
been  previously  placed  on  the  copper  plate,  close  to  the  prepa- 
ration. As  soon  as  the  cacao  butter  begins  to  liquefy,  the 
flame  of  the  lamp  is  diminished,  or  the  lamp  itself  is  removed 
to  a  greater  distance,  until  the  heat  communicated  by  it  to  the 
plate  through  the  rod  is  just  sufficient  to  keep  the  fat  from 
solidifying.  If  it  is  desired  to  employ  higher  temperatures, 
or  to  measure  the  temperature  with  greater  exactitude,  it  is 
necessary  to  have  recourse  to  Strieker's  warm  stage. 

Strieker's  Warm  Stage. — Of  this  there  are  two  forms.  In 
one  the  mode  of  heating,  and  consequently  of  modifying  the 
amount  of  heat  communicated,  is  that  which  has  been  already 
described  (see  Fig.  2).  From  its  simplicity  it  is  well  adapted 
for  the  beginner,  while  it  enables  the  more  practised  observer 
to  maintain  any  desired  temperature  within  very  inconsidera- 
ble limits  of  variation.  The  other,  in  addition  to  the  greater 
exactitude  which  can  be  attained,  has  the  advantage  that,  by 

1  Free  nuclei  of  colored  corpuscles,  which  may  be  seen  if  the  prepa- 
ration has  been  subjected  to  pressure,  must  not  be  confused  with  these 
structures. 


BY    DR.    KLEIN.  23 

its  aid,  it  is  possible  to  continue  the  observation  for  a  long  pe- 
riod. It  is  this  which  is  employed  by  Sanderson  and  Strieker 
for  the  studjr  of  the  circulation  in  mammalia.  For  our  present 
purpose  we  do  not  require  the  whole  apparatus,  so  that  it  is 
onlv  necessary  to  refer  to  those  parts  of  it  which  are  shown  in 
Fig.  3. 

In  the  employment  of  this  apparatus  several  difficulties  are 
encountered.  For  instance,  the  temperature  of  the  water  re- 
ceptacle is  only  in  part  controlled  by  the  regulator.  Then, 
again,  the  temperature  of  the  stage  is  subject  to  variation  ac- 
cording to  the  rate  at  which  the  water  flows  into  and  escapes 
from  it ;  so  that,  if  great  care  be  not  taken  in  the  adjustment, 
constancy  cannot  be  relied  on.  Another  practical  difficulty 
lies  in  the  fact  that  the  temperature  of  the  water  in  the  recep- 
tacle is  different  from  that  in  the  stage,  the  rate  of  flow  being 
so  inconsiderable  that  there  is  necessarily  a  great  loss  of  heat 
by  radiation  from  the  metal  surface.  If  the  stage  be  not  fitted 
with  a  thermometer,  this  difference  of  temperature  may  be  de- 
termined, once  for  all,  by  comparative  measurements,  so  that 
the  true  temperature  of  the  stage  can  then  be  known  at  any 
time  by  deducting  the  ascertained  loss  of  heat,  i.  e.,  the  ascer- 
tained difference  above  referred  to,  from  the  temperature  to 
which  the  regulator  is  adjusted. 

Method  of  varying  the  temperature  rapidly. — In 
connection  with  this  apparatus,  it  is  convenient  to  describe 
the  method  employed  for  subjecting  a  preparation  to  sudden 
alterations  of  temperature.  With  this  view  the  following  con- 
trivance is  used  :  A  clip  is  placed  on  the  tube  leading  from  the 
water  receptacle  (<7,  Fig.  3),  by  means  oX  which  the  access  of 
warm  water  to  the  stage  ma}r  be  interrupted.  The  end  of  the 
escape-tube  (D)  is  then  allowed  to  dip  into  a  vessel  of  cold 
water.  This  done,  cold  water  may  be  readily  introduced  into 
the  stage,  so  as  to  cool  it  suddenly,  by  suction  through  the 
tube  (C),  which  must  be  provided  with  a  branch  (not  shown 
in  the  figure)  between  the  clip  and  the  stage,  for  the  purpose. 
This,  of  course,  at  once  lowers  the  temperature.  To  effect  a 
sudden  rise,  all  that  is  necessary  is  to  open  the  clip.  For  short 
experiments,  it  is  not  necessary  to  have  a  water  receptacle  spe- 
cially constructed  for  the  purpose;  a  large  flask,  supported 
over  a  lamp,  and  without  a  regulator,  may  be  substituted  for 
it,  provided  that,  in  addition  to  the  discharge-tube,  a  thermom- 
eter is  passed  through  the  cork,  in  order  that  the  variations  of 
temperature  may  be  observed,  and  the  application  of  heat  mod- 
ified accordingly. 

Effects  of  Warmth  on  the  Colorless  Corpuscles. — 
We  now  return  to  the  study  of  the  drop  of  newt's  blood,  in- 
closed between  two  cover-glasses,  with  which  we  were  occu- 
pied.    On  subjecting  the  preparation  to  a  temperature  of  38° 


24  BLOOD   CORPUSCLES. 

C,  the  first  fact  that  we  notice  is  that  the  movements  of  the 
colorless  corpuscles  in  general,  and  of  the  granular  ones  in 
particular,  art'  much  more  active.  We  shall  not,  however,  oc- 
cupy ourselves  at  present  with  these,  but  shall  direct  our  atten- 
tion to  the  three  kinds  of  corpuscles  which  we  have  included 
in  our  third  division. 

On  the  warm  stage  we  may  observe  in  these  bodies  (which 
differ  only  in  size)  two  kinds  of  change.  One  of  these  consists 
of  alteration  in  the  form  of  the  protoplasm,  from  the  surface 
of  which  processes  shoot  out  in  all  directions.  This  is  more 
particularly  seen  in  the  forms  we  have  designated  b  and  c. 
In  the  form  a,  although  the  nucleus  at  first  appears  bare,  it  is 
afterwards  seen  to  be  surrounded  by  a  protoplasmic  envelope  ; 
this  may  throw  out  a  pointed  process,  which,  after  stretching 
out  to  a  considerable  length,  is  retracted,  to  be  succeeded  by 
others.  If  the  preparation  is  kept  for  a  length  of  time  at  38°, 
the  elements  of  the  form  a  undergo  other  remarkable  altera- 
tions. They  become  strongly  refractive,  lose  their  double 
contour  and  sharplj'-defined  aspect,  and  acquire  a  form  which, 
at  first  globular,  subsequently  exhibits  constrictions;  so  that 
they  become  in  succession  kidney-shaped,  dumb-bell  shaped, 
and  rosette-shaped,  until  they  eventually  assume  a  nodulated 
aspect.  In  the  course  of  the  process  it  is  common  to  observe 
the  furrows  or  constrictions  forming,  disappearing,  and  reap- 
pearing repeatedl}';  but,  sooner  or  later,  they  become  more  and 
more  distinct  and  complete,  so  that  the  body  assumes  the  ap- 
pearance of  a  clump  of  highly  refractive  minute  globules.  Con- 
sidering the  coincidence  of  the  changes  of  form  and  aspect  of 
the  nucleus  with  those  which  occur  simultaneously  in  the  cell, 
it  is  scarcely  possible  to  doubt  the  dependence  of  the  former 
upon  the  latter,  especially  if  we  bear  in  mind  the  concomitant 
changes  in  optical  properties.  So  that  we  must  regard  these 
appearances  as  indicating  that  the  nuclei  take  an  active  part 
in  the  changes  of  form. 

In  the  form  c  the  cell-substance  itself  may  be  also  the  seat 
of  a  process  of  division.  In  one  instance  at  least  I  have,  of 
course  after  many  hours  of  observation,  witnessed  the  division 
of  a  cell  which  originally  contained  five  nuclei.  The  cell  in 
question  in  the  first  place  exhibited  a  transverse  furrow  :  this 
became  deeper  and  deeper,  so  that,  eventually,  two  masses 
were  formed,  united  together  by  a  neck,  the  smaller  containing 
two  nuclei,  the  larger  three.  These  nuclei  had  already  under- 
gone the  process  of  cleavage  above  described.  By  the  length- 
ening, thinning  out,  and  final  rupture  of  the  isthmus,  the  two 
corpuscles  came  apart.  In  the  larger  of  the  two,  which  was 
now  exclusively  observed,  there  appeared  gradually  two  boss- 
like prominences,  each  of  which  contained  a  number  of  small 
bodies  resulting  from  the  cleavage  of  the  nuclei.     By  the  con- 


BY   DR.    KLEIN.  25 

striction  of  the  base  of  each  of  these  prominences  it  gradually 
separated  from  the  rest  of  the  cell.  One  of  them,  after  separa- 
tion, sent  out  a  process  ;  in  the  other,  no  alteration  of  form 
could  be  observed.  It  is  probable  that  the  forms  a  and  b  are 
the  offspring  of  c. 

On  the  warm  stage,  division  can  also  be  observed  in  the  first 
and  second  variety  of  colorless  corpuscles.  Thus,  for  example, 
it  sometimes  happens  that  the  process  described  only  results 
in  actual  separation  by  rupture  of  the  filament.  In  other  cases 
a  corpuscle  undergoes  division  by  a  process  of  cleavage,  pre- 
ceded by  the  repeated  formation,  disappearance,  and  reappear- 
ance of  furrows.  In  all  cases  of  real  division  it  is  to  be 
observed  that  the  }'Oung  cells  produced  exhibit  very  active 
movements,  changing  thereb}'  in  form  and  place. 

Colorless  Corpuscles  of  Man. — The  mode  of  examining 
the  colorless  corpuscles  of  other  classes  of  animals  is  similar 
to  that  above  described.  It  is,  however,  necessary  to  add  some 
observations  as  to  the  characters  which  these  bodies  present 
in  human  blood.  A  drop  of  blood,  taken  from  the  finger,  is 
placed  between  two  cover-glasses,  as  above  described,  and 
examined  on  the  warm  stage  at  a  temperature  of  38°  C.  The 
human  colorless  corpuscles  are  smaller  than  those  of  the  newt, 
and  exhibit  much  less  variety  in  their  appearance.  They  are 
either  quite  pale,  or  they  contain  a  variable  number  of  dark 
granules.  The  movements  are  less  active  than  those  of  newt's 
blood,  but  sometimes  are  comparable  with  them.  When  they 
are  more  active  than  usual,  the  mode  in  which  their  processes 
are  thrown  out  and  retracted,  and  the  characters  of  their  pro- 
gressive movement  correspond  witli  the  descriptions  already 
given.  On  one  occasion  I  have  observed  movements  which 
were  even  more  lively  than  those  commonly  seen  in  the  newt, 
and  resembled  those  of  rhizopods  in  the  extreme  rapidity  with 
which  the  successive  protrusion  of  processes,  and  corresponding 
interstitial  fluxion  of  the  protoplasm  occurred.  This  happened 
in  the  case  of  a  patient  suffering  from  hemorrhagic  ansemia. 

Feeding  of  Colorless  Corpuscles. — We  have  now  to 
study  the  faculty  possessed  by  the  colorless  corpuscles  of 
taking,  by  virtue  of  their  amoeboid  movement,  solid  particles 
into  their  substance.  For  this  purpose  we  emplo}^  either  finely- 
divided  fatty  substances  or  coloring  matters.  The  subject  is 
of  great  interest  in  relation  to  the  mode  in  which  amoeboid 
cells  take  in  nourishment.  To  the  histologist  it  is  further  of 
Importance,  as  affording  him  a  means  by  which  to  mark  indi- 
vidual corpuscles,  so  as  to  follow  them  in  their  wanderings 
through  the  organism.  The  materials  used  are  the  following: 
".  Vermilion.  Tins  is  prepared  I13'  prolonged  trituration  in 
a  half  per  cent,  solution  of  common  salt.  b.  Carmine.  Car- 
mine is  dissolved  in  as  little  liquor  ammonias  as  possible,  in  a 


26  BLOOD   CORPUSCLES. 

small  beaker,  and  filtered.  Common  concentrated  (commer- 
cial) acetic  acid  is  then  added  with  agitation,  until  a  drop  of 
the  mixture,  when  examined  under  a  low  power,  is  seen  to  con- 
tain granules.  If  too  much  is  added,  the  precipitate  is  not 
fine  enough.  The  latter  is  then  to  be  separated  by  careful 
decantation,  and  suspended  in  a  half  per  cent,  salt  solution  as 
before.  It  is  well  to  dilute  the  liquid  with  its  bulk  of  serum 
before  using  it.  c.  Aniline  Blue  is  dissolved  in  common  me- 
thylated spirit,  and  filtered.  Water  or  salt  solution  must  then 
be  added  gradually,  so  as  to  obtain  a  fine  precipitate,  the 
resulting  liquid  being  mixed  with  serum  as  above,  d.  Fresh 
Milk. 

If  it  is  intended  to  watch  the  process  of  feeding,  a  small 
drop  of  blood,  to  which  one  of  the  liquids  above  mentioned 
has  been  added,  is  examined,  either  in  the  ordinary  way,  in  the 
case  of  amphibian  blood,  or  on  the  warm  stage  if  mammalian 
blood  is  employed.  If  our  object  is  merely  to  observe  corpus- 
cles already  fed,  the  liquids  in  question  may  be  injected  either 
into  the  jugular  vein  (of  rabbits  or  guineapigs)  or  into  the 
abdominal  vein  (of  frogs),  care  being  taken  to  empio}'  a  suffi- 
ciently large  quantity.  After  10-30  minutes,  a  drop  of  blood 
may  be  taken  for  examination.  (See  Chapter  VII.,  as  to  in- 
jection into  the  veins,  and  Chapter  VIII.,  as  to  the  lymphatic 
system.)  Whichever  plan  is  adopted,  it  is  alike  possible  to 
satisfy  ourselves  that  the  cells  not  only  take  in  foreign  bodies, 
but  that  they  also  have  the  faculty  of  discharging  them,  and 
further,  that  when  one  cell  comes  into  contact  with  another,  it 
often  gives  up  to  it  the  solid  bodies  which  it  has  itself  before 
ingested.  In  general,  the  tendencj7  to  ingestion  varies  with 
the  activity  of  the  amoeboid  movement,  for  the  first  thing 
observed  is  an  adhesion,  either  of  the  surface  of  the  central 
part  of  the  corpuscle,  or  of  a  process  to  the  foreign  body,  fol- 
lowed by  a  retraction  of  the  adherent  part  into  its  substance. 

Application  of  Liquid  Reagents. — It  is,  in  the  first 
place,  of  importance  to  ascertain  what  liquids  can  be  added 
without  affecting  the  vital  phenomena  of  the  colorless  corpus- 
cles. Such  are  designated  by  the  adjective  indifferent,  and 
are  those  which  are  always  to  be  used  in  the  study  of  fresh 
living  tissues.  For  example,  we  may  use  fresh  serum  or  tran- 
sudation liquids,  as  also  the  aqueous  humour  of  the  eye,  which 
has  the  important  advantage  of  being  entirely  free  from  formed 
elements.  The  most  commonly  used  indifferent  liquid  is  the 
half  per  cent,  solution  of  common  salt  already  mentioned, 
which  is  of  great  value ;  although,  as  may  be  readily  under- 
stood, it  is  not  altogether  without  action  on  living  tissues.  In 
the  examination  of  blood,  it  is  added  as  a  preparatory  step  to 
the  addition  of  other  reagents.  With  this  view  the  solution 
is  dropped  from  a  capillary  pipette  (Fig.  4)  upon  a  slide;  a 


BY    DR.    KLEIN.  27 

drop  of  newt's  blood  being  then  added  to  it  and  covered.  It 
is  seen  that  the  colorless  corpuscles  have  undergone  no  mate- 
rial change,  but  that,  in  some  instances,  their  movements  are 
not  quite  so  active.  The  colored  corpuscles,  which  in  our 
previous  examination  we  have  disregarded,  are  now  seen  as 
smooth  oval  elliptical  disks,  which,  when  looked  at  edgewise, 
present  an  outline  as  if  they  were  oblong  rods.  Those  which 
lie  horizontally  look,  for  the  most  part,  like  greenish-yellow 
bodies  of  oval  form;  in  some  of  which  we  can  distinguish  a 
central  elliptical  nucleus.  Soon,  changes  occur,  in  consequence 
of  which  the  color  becomes  unequally  distributed,  the  margins 
are  more  or  less  curved,  or  the  surfaces  marked  with  what  look 
like  folds.  These  appearances  are  referable  probably  to  a  pro- 
cess analogous  to  coagulation. 

Method  of  Retarding  Evaporation.— If  it  is  intended 
to  keep  a  preparation  of  this  kind  long  under  observation,  it 
is  necessary  to  add  saline  solution  from  time  to  time  from  a 
pipette.  If,  however,  as  is  often  the  case,  it  is  of  importance 
to  keep  an  individual  corpuscle  in  the  field,  this  method  can- 
not be  employed  without  great  risk  of  the  object  being  carried 
away  by  the  stream.  To  avoid  this  result,  it  is  a  good  plan 
to  place  a  drop  or  two  of  solution  near  each  of  two  opposite 
margins  of  the  cover-glass.  Ity  these  drops  the  liquid  under 
the  glass  is  preserved  from  evaporation,  because  the  space  in 
the  immediate  neighborhood  of  the  margin  is  kept  saturated 
with  moisture. 

We  may  now  proceed  to  study  the  action  of  other  reagents 
on  blood  already  treated  with  saline  solution.  We  use  the 
so-called  method  of  irrigation.  On  one  side  of  the  cover- 
glass  a  small  strip  of  blotting-paper  is  placed,  while  the  re- 
agent is  discharged  from  the  pipette  at  the  opposite  edge. 
When  the  paper  has  become  saturated  with  liquid  it  is  replaced 
by  another,  and  the  process  repeated,  so  that  a  constant  cur- 
rent is  maintained  through  the  preparation.  If  the  colored 
corpuscles  are  the  special  subject  of  study,  it  is  best  to  wait 
until  they  have  shrunk,  for  we  are  then  sure  that  many  of 
them  will  have  had  time  to  sink  and  adhere  to  the  surface  of 
the  slide.  If  this  precaution  is  neglected,  they  are  apt  to  be 
swept  away  by  the  current. 

Action  of  Distilled  Water. — In  blood  preparations  irri- 
gated with  distilled  water,  the  movements  of  the  colorless 
blood  corpuscles  gradually  cease.  The  inequalities,  corre- 
sponding to  the  processes,  disappear,  while  the  corpuscle  en- 
larges, and  assumes  the  globular  form.  From  one  to  four  (or 
even  more)  round  vesicular  nuclei  come  into  view.  Soon  the 
nuclei  coalesce  to  form  a  single  mass,  also  having  a  vesicular 
character,  which  not  un frequently  exliibits  a  rotatory  move- 
ment within  the  corpuscle.     The  substance  which  surrounds 


28  BLOOD   CORPUSCLES. 

the  nucleus  is  pale.  It  contains  numerous  distinct  granules, 
which  show  active  Brownian  movement.  It  not  unfrequently 
happens,  that  a  much-swollen  spheroidal  corpuscle,  after  re- 
maining a  length  of  time  in  its  place  without  change,  is  torn 
away  from  its  attachment  to  the  glass  by  the  current,  in  which 
case  it  may  either  divide  into  two  masses,  one  < »f  which  con- 
tinues adherent,  while  the  other  floats  away,  or  it  may  float 
away  en  masse,  leaving  behind  it  a  long  filament,  b}'  which  it 
is  still  connected  with  its  original  point  of  adhesion.  By  re- 
newing the  irrigation,  the  filament  will  probably  be  severed. 
It  is  thus  proved  that  the  colorless  corpuscle  consists  of  a  soft 
viscous  substance.  The  final  result  of  the  action  of  water  on 
the  colorless  corpuscles  is  always  disintegration;  the  mass 
suddenly  disperses  into  the  surrounding  medium,  all  that  re- 
mains of  the  previously  so  active  entity  is  a  collapsed,  form- 
less clump,  in  which  one  or  two  motionless  granules  may  be 
seen. 

In  the  colored  blood  disks,  the  first  change  is  that  their 
surfaces  become  smooth,  their  contour  becomes  circular,  the 
nucleus  rounder  and  brighter  than  before,  the  corpuscle  paler 
and  paler,  until  its  outline  is  scarcely  distinguishable.  Two' 
phenomena  are  worth  noticing  before  we  proceed  further. 
The  first  is,  that,  at  the  commencement  of  irrigation  with  dis- 
tilled water,  it  occasionally  happens  that,  immediately  their 
surfaces  have  become  smooth,  the  corpuscles  suddenly  assume 
a  rounder  and  smaller  appearance,  and  are  more  intensely 
colored:  quickly  returning,  however,  to  the  elliptical  form, 
and  losing  their  color  as  before.  The  second  will  be  explained 
later:  a  colored  corpuscle  appears  to  have  separated  into  two 
parts,  a  pale  elliptical  disk  and  a  yellow  mass,  occupying  a 
central,  or,  more  frequently,  an  eccentric  position  within  it, 
from  which  colored  processes  often  stretch  out  like  rays 
toward  the  periphery. 

Strieker's  Method. — There  is  another  method  of  stiutying 
the  action  of  water  on  the  colored  corpuscles.  Fortius  pur- 
pose wre  require  the  warm  stage  (Fig.  2).  A  drop  of  water  is 
placed  on  the  floor  of  the  chamber,  and  on  the  middle  of  the 
surface  of  the  cover-glass  a  drop  of  blood,  either  pure  or  di- 
luted with  salt  solution.  The  cover-glass  is  then  inverted 
over  the  chamber,  the  edges  of  which  have  been  previouslj' 
oiled,  or  surrounded  with  a  ring  of  putty,  so  that  it  is  air- 
tight. By  wanning  the  copper  wire  the  water  is  made  to 
evaporate  from  the  floor  of  the  chamber,  and  becomes  con- 
densed on  the  under  surface  of  the  cover-glass.  In  this  way 
we  are  enabled  to  study  the  gradual  action  of  water  on  the 
corpuscles  very  advantageously. 

Action  of  Salt  Solution  on  the  Blood  Corpuscles  of 
Mammalia. — In  mammalian  blood  which  has  been  diluted 


BY   DR.    KLEIN.  29 

with  salt  solution,  the  naturally  bi  concave  colored  corpuscles 
exhibit  a  remarkable  alteration,  which  consists  in  their  assum- 
ing a  form  very  similar  to  that  of  the  fruit  of  the  horse-chest- 
nut. In  those  corpuscles  which  present  their  surfaces,  the 
processes  which  project  from  the  margin  look  like  the  rays  of 
a  star,  while  those  which  spring  from  the  surface  appear  as 
dark  points.  In  such  a  preparation  it  is  not  difficult  to  float 
away  the  colored  disks  altogether,  by  irrigating  it  immedi- 
ately with  salt  solution.  The  colorless  corpuscles  sink  very 
rapidly,  and  stick  to  the  glass,  while  the  colored  disks  remain 
suspended. 

Let  us  seek  for  a  field  in  which  one  or  two  colorless  corpus- 
cles only  are  to  be  seen.  By  discontinuing  the  irrigation,  at 
the  same  time  replacing  the  bit  of  blotting-paper  so  as  to  with- 
draw the  fluid,  we  bring  the  cover  so  near  the  slide  that  it 
compresses  the  corpuscles,  which  in  consequence  appear  paler 
and  larger.  The  paper  is  now  taken  away,  and  salt  solution 
added  at  the  opposite  edge  as  before.  The  corpuscles  at  once 
become  smaller  and  more  globular,  and  seem  to  contract;  but, 
immediately  after,  dilate  again,  as  if  they  were  relaxing.  In 
the  resumption  by  the  corpuscle  of  its  original  form  after 
compression,  we  have  to  do  with  a  phenomenon  which  can  only 
be  explained  on  the  supposition  that  the  colorless  corpuscle  is 
elastic.  The  nature  of  the  contraction  and  the  subsequent  re- 
laxation lead  us,  however,  to  suppose  that  the  contraction  is, 
at  least  partly,  a  result  of  the  excitation  produced  by  the  irri- 
gation with  saline  solution. 

Action  of  Water  on  Mammalian  Blood. — As  regards 
the  action  of  water  on  the  corpuscles  of  mammalian  blood, 
there  is  not  much  to  be  added  to  what  has  been  said  with  re- 
ference to  newt's  blood  ;  the  colorless  corpuscles  discontinue 
their  movements,  become  globular  in  form,  exhibit  vesicular 
nuclei  and  vibrating  granules,  and  finally  are  disintegrated. 
The  colored  disks  lose  their  horse-chestnut  form,  become 
smooth  and  pale,  and  eventual]}'  disappear. 

Action  of  Acids. — The  general  action  of  acids  is  so  uni- 
form that  it  is  not  necessary  to  refer  separately  to  each.  We 
content  ourselves  with  describing  the  action  of  acetic  acid.  A 
special  action  of  boracic  acid  will  be  noticed  further  on.  The 
final  result  of  the  action  of  acetic  acid  on  the  blood  corpuscles 
is  the  same,  whether  it  is  diluted  or  concentrated.  The  rapid- 
ity witli  which  the  changes  take  place  is,  however,  different.  It 
is  always  better  to  begin  with  dilute  acid.  If  a  salt  solution 
preparation  of  newt's  blood  is,  after  the  shrinking  of  the  colored 
corpuscles,  irrigated  with  a  liquid  containing  one  per  cent,  of 
the  ordinary  commercial  acid,  we  observe,  first,  that  the  move- 
ments of  the  colorless  corpuscles  cease,  and  that  they  enlarge 
and  display  their  nuclei  as  sharply-defined  bodies,  beset  with 


30  BLOOD   CORPUSCLES. 

granules.  If  the  action  of  the  acid  1ms  been  prolonged,  each 
corpuscle  appears  to  consist  of  two  parts — a  distinctly  gran- 
ular mass,  which  immediately  surrounds  the  nucleus,  and  a 
bright  transparent  circle,  with  sharp  outline,  within  which 
that  body  is  inclosed.  The  nuclei  are  furrowed  in  such  a  way 
that  their  form  is  very  variable,  and,  if  the  action  has  lasted 
long  enough,  they  look  as  if  actually  split  into  smaller  par- 
ticles. The  colored  corpuscles  again  become  smooth,  swell  out 
somewhat,  become  cellular  in  their  contour,  just  as  after  the 
addition  of  water,  each  showing  an  oblong  granular  nucleus, 
which  is  at  first  smooth,  subsequently  uneven  and  rough. 
Many  of  the  blood  disks  return  to  their  original  elliptical  form. 
All  eventuall}' lose  their  color,  but  possess,  even  when  entirely 
colorless,  a  much  more  distinct  contour  than  those  which  have 
been  acted  upon  by  water.  Occasionally,  it  happens  that  the 
nucleus  becomes  stained  with  coloring  matter,  and  assumes  a 
yellow  tint.  In  human  blood,  the  colorless  corpuscles  exhibit, 
after  the  action  of  acetic  acid,  the  appearance  of  globular  bodies, 
in  which  two,  three,  or  more  small  shrunken  nuclei  are  visible. 
The  colored  disks  lose  their  stellate  form  and  their  coloring 
matter,  but  their  outlines  are  still  distinct. 

Action  of  Alkalies. — If  a  salt  solution  preparation  is  irri- 
gated with  an  alkaline  liquid,  whatever  be  the  source  of  the 
blood  used,  the  colorless  corpuscles  at  first  swell,  and  then 
rapidly  disappear.  The  colored  disks  also  swell  out  at  first — 
those  of  mammalia  becoming  often  what  German  authors  have 
designated  napfformig  (cup-shaped);  eventually  they  lose 
their  color  and  disappear. 

Action  of  Boracic  Acid. — We  have  now  to  describe  a 
reaction  which,  especially  in  the  blood  of  the  newt,  is  of  im- 
portance, as  serving  to  illustrate  the  intimate  structure  of  the 
colored  blood  disk.  The  action  of  a  two  per  cent,  solution  of 
boracic  acid  on  the  colorless  corpuscles  in  general,  and  on  the 
blood  disks  of  mammalia,  does  not  differ  from  that  of  other 
weak  acids.  If,  however,  a  salt  preparation  of  newt's  blood,  in 
which  the  colored  corpuscles  have  already  sunk,  is  irrigated 
with  the  solution  in  question,  we  observe  that  those  bodies 
swell  and  acquire  a  circular  contour,  showing,  at  the  same  time, 
a  pale  oval  nucleus.  It  is  now  seen  that,  as  the  disk  grad- 
ually pales,  the  nucleus  becomes  more  and  more  spheroidal 
and  yellow,  while,  at  the  same  time,  it  increases  in  size.  At 
first  it  is  smooth,  subsequently  uneven.  Here  and  there  cor- 
puscles are  met  with  in  which  the  yellow  central  body  (zooid 
of  Briicke)  is  not  round,  but  beset  with  processes  which  stretch 
like  rays  towards  the  periphery.  Occasional^',  it  can  be  made 
out  that  the  processes  are  withdrawn,  so  that  the  j'ellow  centre 
acquires  a  roundish  form.  The  zooids  eventually  lose  their 
central  position,  and  if  the  preparation  is  protected  from  evapo- 


BY    DR.    KLEIN.  31 

ration  for  a  sufficient  length  of  time,  the  observer  is  sure  to  see 
man}'  corpuscles  in  which  the}7  lie,  some  parti}-,  some  entirely 
outside  of  the  outline  of  the  pale  disk.  The  latter  (again  fol- 
lowing Briicke)  we  designate  cecoid.  Briicke  teaches  that  the 
zooid  consists  of  the  nucleus  and  the  haemoglobin  ;  that  it  with- 
draws from  the  cecoid  which  it  previously,  as  it  were,  inhab- 
ited, and  collects  itself  around  the  nucleus,  so  as  to  form  an 
independent  individual,  capable  of  a  separate  existence.  In 
describing  further  on  similar  appearances  observed  during  the 
action  of  carbonic  acid  gas,  we  shall  suggest  another  explana- 
tion of  the  phenomenon. 

Action  of  Tannin  on  Human  Blood — Roberts's  Re- 
action.— The  action  of  tannin  on  the  colored  corpuscles  of 
human  blood  resembles  that  of  boracic  acid  on  newt's  blood. 
When  two  per  cent,  solution  of  tannin  is  added  to  human 
blood,  the  corpuscles,  which  have  been  already  rendered  star- 
shaped  by  salt  solution,  acquire  an  even  contour.  Soon  after, 
a  sharply-defined,  yellowish-green,  roundish  body  is  seen,  either 
just  within  or  at  the  margin  of  each  corpuscle,  or  even  out- 
side of  it,  while  the  corpuscle  itself  has  become  colorless. 

Action  of  Gases  on  the  Blood. — For  the  study  of  the 
action  of  oxygen  and  carbonic  acid  gas  on  the  blood  corpus- 
cles, either  of  the  movable  stages  represented  in  Figs.  2,  3, 
and  16  may  be  used.  Around  the  edge  of  the  central  chamber 
we  form  an  annular  wall  of  putty.  We  then  make  on  a  cover- 
glass  a  preparation  of  newt's  blood,  to  which  about  half  its 
volume  of  distilled  water  has  been  added.  The  glass  is  then 
inverted  over  the  chamber  (upon  the  floor  of  which  a  drop  of 
water  has  previously  been  placed)  with  the  preparation  down- 
wards, so  that  its  entire  periphery  presses  evenly  upon  the 
putty  ring.  The  chamber  is  thus  converted  into  an  air-tight 
cavity.  In  Fig.  3,  two  tubes  (H,  I),  with  India-r.ubber  con- 
nectors fitted  to  them,  are  shown,  both  of  which  communicate 
with  the  chamber  in  such  a  way  that  when  it  is  closed  above 
and  below,  a  stream  of  gas  passing  in  by  the  one  escapes  by 
the  other.  By  means  of  an  apparatus  in  communication  with 
the  tube  H,  the  construction  of  which  will  be  readily  under- 
stood from  Fig.  5,  the  observer  is  able  to  fill  the  chamber  at 
will  with  carbonic  acid  gas  or  with  air.  This  is  accomplished 
as  follows: — 

If  the  bottle  containing  hydrochloric  acid  is  raised,  the  clip 
n  opened,  and  the  India-rubber  tube  a  shut  between  the  teeth, 
the  carbonic  acid,  which  is  developed  in  M,  after  it  has  passed 
through  the  wash-bottle  V,  flows  into  the  chamber,  and  is  dis- 
charged by  the  tube  b.  By  proceeding  in  this  manner  one 
hand  is  left  free,  and  can  be  used  for  adjustment.  To  inter- 
rupt the  current  of  gas,  all  that  is  necessary  is  to  close  N  and 


32  BLOOD   CORPUSCLES. 

to  let  down  the  bottle.  The  carbonic  acid  gas  in  the  chamber 
is  easily  replaced  by  air,  by  aspiration  through  the  tube  a. 

Action  of  Carbonic  Acid  Gas. — The  preparation  having 
been  brought  into  focus,  the  gas  is  allowed  to  pass  through 
the  chamber  for  a  short  time.  At  first,  the  only  observable 
effect  is  that  the  nuclei  of  the  slightly  smoother  disks  are  more 
distinct.  If  the  carbonic  acid  is  now  replaced  by  air,  the  nuclei 
again  become  indistinguishable.  We  have  to  do,  therefore, 
with  a  transitory  coagulation  of  the  substance  surrounding 
the  nucleus.  An  excess  of  the  gas  brings  the  nuclei  perma- 
nently into  view.  If,  however,  we  first  add  to  our  preparation 
a  quantity  of  water,  sufficient  not  merel}'  to  swell  the  colored 
disks,  but  to  deprive  them  partly  of  their  color,  the  result  is 
somewhat  different.  After  a  short  action  of  the  gas,  the  ap- 
pearances are  much  as  they  have  been  already  described ;  but, 
if  an  excess  is  admitted,  bodies  similar  to  the  zooids  above 
described  as  produced  by  the  action  of  boracic  acid,  come  into 
view. 

Instead  of  the  pale  oblong  nuclei,  the  areas  of  the  decolor- 
ized disks  inclose  relatively  large,  yellow,  roundish  bodies,  both 
the  areas  and  the  inclosed  bodies  being  beset  with  fine  gran- 
ules. In  those  disks  which  have  previously  lost  their  color, 
and  are  consequently  scarcely  visible,  the  nuclei  become  visi- 
ble after  the  addition  of  excess  of  carbonic  acid,  as  pale 
granulous  bodies,  the  disks  themselves  also  containing  nume- 
rous granules.  If  we  now  replace  the  carbonic  acid  by  air, 
the  corpuscles  recover,  in  every  respect,  their  previous  aspect ; 
those  in  which  the  zooids  had  come  into  view  becoming  smooth, 
and  of  uniform  color,  so  that  neither  nucleus  nor  granules  can 
be  distinguished.  Those  disks  which  have  lost  their  color  by 
the  action  of  water  become,  as  before,  uniformly  pale  and  in- 
distinct. The  experiment  may  be  repeated  several  times.  It 
is  not  difficult  to  explain  all  these  appearances  by  coagulation. 

It  is  a  very  good  plan,  in  order  to  study  the  action  of  car- 
bonic acid  on  newt's  blood,  in  all  degrees  of  dilution,  to 
examine  a  salt  solution  preparation  of  such  blood  on  the  mov- 
able stage  (Fig.  2),  which  also  serves  the  purpose  of  a  gas 
chamber.  On  warming  the  metal  rod,  water  vapor  is  disen- 
gaged from  the  floor  of  the  chamber  (into  which  a  drop  of 
water  has  been  previously  introduced),  and  acts  upon  the  cor- 
puscles. 

In  order  to  study  the  action  of  carbonic  acid  on  the  colored 
corpuscles  of  man,  it  is  best  to  employ  a  drop  of  blood  mixed 
with  salt-solution,  taking  care  that  the  individual  cells  are  as 
much  as  possible  separate  from  one  another.  If,  as  soon  as 
the  corpuscles  become  horse-chestnut  shaped  in  consequence 
of  the  action  of  the  salt-solution,  the  preparation  is  subjected 
to  the  action  of  the  gas,  we  at  once  observe  that  the  acuminate 


BY   DR.    KLEIN. 


33 


projections  on  the  surface  of  the  corpuscles  become  less  marked 
in  consequence  of  the  levelling  up  of  the  intermediate  parts  ; 
and,  although  there  are  many  which  do  not  resume  the  bicon- 
cave form,  being  still  saucer-shaped,  they  all  have  even  surfaces. 
If  the  carbonic  acid  is  replaced  by  air,  the  corpuscles  again 
become  horse-chestnut  shaped.  This  reaction  may  also  be 
witnessed  several  times  in  succession.  The  disappearance  of 
the  stellate  form  may  be  explained  on  the  supposition  that  a 
spontaneously  coagulated  constituent  is  redissolved  under  the 
action  of  carbonic  acid.  Colorless  corpuscles  show  their  nuclei 
when  acted  on  by  carbonic  acid,  but  are  otherwise  unaltered. 

Action  of  Electricity.— If  it  is  intended  to  subject  blood 
to  the  action  of  electrical  discharges,  or  of  the  constant  or  in- 
terrupted current,  we  place  a  small  drop  of  blood  on  the  slide 
(Fig.  6)  in  such  a  position  that,  when  it  is  covered,  it  spreads 
between  the  two  poles  of  tinfoil,  which  we  connect  by  means 
of  either  of  the  appliances  shown  in  the  figure  with  the  secon- 
dary coil  of  the  induction  apparatus. 

According  to  Rollett,  it  is  advisable,  in  using  electrical  dis- 
charges, that  the  tinfoil  points  should  be  six  millimetres  apart. 
The  Leyden  jar  should  have  a  surface  of  500  square  centi- 
metres, and  give  a  spark  one  millimetre  long.  If,  then,  the 
discharges  succeed  each  other  at  intervals  of  from  three  to  five 
minutes"  the  following  changes  are  observed  in  the  colored  cor- 
puscles of  man.  Firstly,  the  circular  disks  become  slightly 
crenate.  This  effect  gradually  increases,  the  corpuscles  become 
rosette-shaped,  then  mulberry-shaped,  and  finally,  by  the  acu- 
mination  of  the  projections,  horse-chestnut  shaped.  Later,  the 
processes  are  withdrawn,  the  blood  corpuscle  becomes  round, 
and,  at  last,  pale.  In  the  corpuscles  of  the  newt  and  frog  the 
effects  are  not  dissimilar.  They  become  wrinkled  and  dappled, 
but  these  appearances  are  very  transitory,  and  they  are  again 
seen  to  be  circular  and  pale,  while  the  nucleus  becomes  round 
and  sharply  defined.  Not  unfrequently  it  happens  that  one  or 
more  blood  corpuscles  coalesce  before  they  lose  their  color,  or 
that  (in  amphibian  blood)  the  nucleus  is  discharged  while  the 
disk  is  still  yellow.  The  effects  produced  by  induction  cur- 
rents are  altogether  analogous  to  those  ahove  described.  Un- 
der the  action  of  the  constant  current  (a  single  Bunsen's  cell) 
the  corpuscles  next  the  electrodes  undergo  changes,  which  at 
the  negative  pole  correspond  to  the  action  of  an  acid,  at  the 
positive,  to  that  of  an  alkali.  In  a  salt  preparation  of  batra- 
chian  blood  examined  near  the  positive  pole,  the  nucleus  comes 
fust  into  view,  and  then  the  corpuscles  lose  their  color.  In  a 
similar  preparation  of  human  blood  in  which  the  corpuscles 
are  horse-chestnut  shaped  already,  they  become  smooth,  lose 
their  color,  and  disappear. 

The  colorless  corpuscles,  when  excited  electrically  during 
3 


34  BLOOD   CORPUSCLES. 

their  amoeboid  movements,  assume  the  spheroidal  form.  Their 
movements,  however,  are  resumed  as  soon  as  the  excitation  is 
discontinued.  The  motion  is  more  undulating  than  before, 
but  soon  recovers  its  former  character.  After  repeated  excita- 
tion the  corpuscles  expand  into  lamina',  but  still  exhibit 
changes  of  form.  Under  the  influence  of  successive  shocks  of 
greater  intensity,  the  colorless  corpuscles  swell  out,  their 
granules  exhibiting  molecular  movement,  and  finally  disappear. 

Blood  Crystals. — In  concluding  this  chapter,  we  propose 
to  give  the  most  simple  methods  of  obtaining  crystals  of  luemo- 
globin  and  hsemin  for  microscopic  purposes,  referring  the  reader 
for  more  detailed  information  to  Chapter  XV. 

Haemoglobin. — A  large  drop  of  blood  is  taken  directly 
from  a  living  guineapig,  and  allowed  to  coagulate  on  a  watch- 
glass.  We  now  add  a  small  quantity  of  water,  and  then, 
taking  up  the  clot  with  the  forceps,  let  fall  on  a  glass  slide 
several  small  drops.  As  these  drops  evaporate  haemoglobin 
crystals  of  varying  size  shoot  out  from  the  edge,  separately 
and  in  bunches. 

Another  plan  is  to  cut  out  the  heart  and  great  vessels  of  a 
recently  killed  guineapig,  placing  them  on  a  watch-glass  in 
saturated  air  for  twenty-four  hours.  Then  take  some  blood 
from  the  heart  by  means  of  a  capillary  tube,  and  allow  a  very 
small  drop  to  fall  into  an  equally  small  drop  of  water  on  a 
slide.  As  it  evaporates,  crystals  are  formed  as  before.  This 
method  does  not  answer  with  rabbit's  blood. 

Heemin  Crystals. — The  simplest  method  of  obtaining 
hsemin  crystals  is  the  following:  A  small  quantity  of  dried 
mammalian  blood  (human  will  do)  is  placed  on  a  slide.  A  few 
small  crystals  of  common  salt  are  then  added,  and  a  cover- 
glass  placed  over.  A  drop  of  glacial  acetic  acid  is  then  allowed 
to  enter  from  the  side.  On  warming  the  preparation  carefulty 
until  the  greater  part  of  the  acid  has  evaporated,  an  immense 
number  of  the  reddish-brown  crystals  of  hoemin  are  seen. 

For  a  description  of  the  corpuscles  which  occur  in  the  lym- 
phatic system,  see  the  chapter  treating  of  that  subject.  The 
development  of  the  blood  corpuscles  will  be  described  in  Chap- 
ter VII. 


BY   DR.    KLEIN.  35 


CHAPTER  II. 

EPITHELIUM   AND   ENDOTHELIUM. 

Under  this  heading  are  included  the  epithelium  of  the 
mucous  membranes,  of  the  cornea  and  conjunctiva,  and  of  the 
integument,  and  the  endothelium  of  the  serous  membranes. 
The  epithelium-like  structures  which  are  in  relation  with  the 
nerves  of  the  various  organs  of  sense  will  be  examined  in  Part 
II. 

Ciliated  Cylindrical  Epithelium. — To  investigate  cili- 
ated epithelium  in  the  living  state,  a  frog  should  be  selected, 
and  its  mouth  opened  with  the  handle  of  a  scalpel.  Then, 
using  either  a  lancet-shaped  needle  or  the  blade  of  a  sharp  knife, 
we  scrape  from  the  projection  in  the  roof  of  the  oral  cavit}', 
corresponding  with  the  floor  of  the  orbit,  a  little  of  its  epithe- 
lial covering.  This  is  transferred  to  a  small  drop  of  an  indiffe- 
rent fluid  (half  per  cent,  solution  of  common  salt)  on  a  glass 
slide,  slightly  separated  with  needles,  and  covered  in  the  usual 
manner.  In  such  a  specimen  we  find  not  only  masses  of  epi- 
thelium in  connection,  but  also  smaller  groups  and  single  cells. 
In  the  masses  of  epithelium  we  cannot  distinguish  quite  clearly 
the  individual  cells,  but  on  the  free  border — on  the  coast,  as 
it  were,  of  the  epithelial  island — we  observe  the  exceedingly 
lively  movement  of  the  cilia.  In  addition  we  see  blood  disks, 
small  round  particles  of  protoplasm  and  granules  driven  quick- 
ty  along  in  the  fluid ;  and  from  these  passing  bodies  we  are 
able  to  recognize  the  direction  of  the  movement  of  the  cilia, 
an  observation  which  could  not  otherwise  be  made,  on  account 
of  the  extreme  rapidity  of  that  movement.  In  the  smaller 
epithelial  groups  we  are  able  more  easily  to  recognize  the  in- 
dividual shorts-conical  cells.  These  groups  are  in  more  or 
less  rapid  rotation,  the  rotatory  motion  being  due  to  the  fact 
that  onlj7  one  portion  of  their  surface  is  furnished  with  cilia — 
that,  namely,  which  corresponds  to  the  bases  of  the  conical 
cells. 

Effects  of  Reagents  on  Ciliary  Motion. — Dilute 
Alkalies. — After  some  time  we  perceive  that  the  cilia  here 
and  there  begin  to  strike  more  slowly,  and,  by-and-by,  they 
come  to  rest.  In  a  specimen  prepared  as  above  described, 
which  has  of  course  been  prevented  from  becoming  dry  by  the 
occasional  addition  of  a  drop  of  half  per  cent,  solution  of  com- 
mon salt,  if  we  choose  a  spot  at  which  the  ciliary  movement 


36  EPITHELIUM    AND   ENDOTHELIUM. 

is  either  exceedingly  languid  or  has  ceased  altogether,  and 
cautiousl}r  allow  a  small  quantity  of  a  very  delicate  solution 
of  potash  to  act  upon  it  by  the  irrigation  process,  we  soon  ob- 
serve that  the  motion  is  renewed  ;  becoming  equal  in  rapidity 
to  that  seen  in  the  perfectly  fresh  preparation.  The  restora- 
tion of  motion  is  not  due  to  any  special  property  of  potash ; 
nor  can  it  be  attributed  to  the  influence  of  that  reagent  in  dis- 
solving coagulated  material  between  the  cilia,  which  might  be 
supposed  to  interfere  mechanically  with  their  movements. 
This  is  proved  bj'  the  fact  that  many  other  reagents  act  simi- 
larly as  stimulants  of  ciliary  motion — e.  g.,  distilled  water,  half 
per  cent,  solution  of  common  salt,  dilute  acetic  acid,  carbonic 
acid,  or  the  induced  current  (applied  according  to  the  method 
described  in  Chapter  I.).  All  these,  if  used  with  great  care, 
accelerate  the  movement  in  the  first  instance.  The  accele- 
ration lasts  only  for  a  short  time,  and,  in  most  cases,  is  quick- 
I3*  followed  by  cessation  of  movement,  consequent  upon  the 
destructive  influence  of  the  reagent  used.  After  the  addition 
of  dilute  acetic  acid  (and  still  more  rapidly  with  concentrated) 
the  bodies  of  the  cells  swell  and  become  transparent,  and  their 
nuclei  well  defined,  in  the  same  manner  as  after  the  addition 
of  water.  The  investigation  of  the  respective  actions  of  carbo- 
nic acid  gas  and  oxygen  upon  ciliary  movement  is  a  very  im- 
portant experiment.  We  make  a  preparation  of  the  ciliated 
epithelium  from  the  throat  of  the  frog,  in  a  half  per  cent,  solu- 
tion of  common  salt  upon  a  cover-glass,  which  is  then  placed 
on  a  ring  of  putty  over  the  gas-chamber  of  the  movable  stage 
(Fig.  2).  Into  this  chamber  a  drop  of  water  has  been  previous- 
ly placed  to  keep  it  moist,  and  if  we  now  allow  a  stream  of 
carbonic  acid  to  pass,  we  perceive,  as  has  been  already  men- 
tioned, that  for  a  few  moments  the  ciliary  motion  becomes 
quicker,  but,  by-and-by,  slower,  until  it  finally  ceases.  On 
now  substituting  atmospheric  air  (oxygen),  we  find  that  the 
movement  slowly  recommences,  and,  before  long,  is  quite  as 
active  as  before  the  passage  of  the  carbonic  acid.  The  experi- 
ment ma}r  be  repeated  several  times  with  a  like  result,  until  at 
last  the  motion  can  no  longer  be  excited.  Ox3'gen  is  there- 
fore as  essential  for  the  continuance  of  motion  in  the  indi- 
vidual ciliated  cell  as  for  the  maintenance  of  animal  life  in 
general. 

Study  of  Ciliary  Motion  in  Situ. — To  demonstrate 
ciliary  action  on  a  membrane  in  situ,  the  most  judicious  plan 
is  to  remove  from  a  female  frog  or  toad  that  portion  of  peri- 
toneum which  covers  the  cisterna  hjmphatica  magna,  the  so- 
called  septum  of  the  cisterna.  Or,  instead  of  this,  a  portion 
of  the  parietal  peritoneum  of  the  anterior  abdominal  wall  of 
the  newt  may  be  employed.  In  either  case,  the  part  removed 
is  to  be  quickly  and  carefully  spread  upon  a  glass  slide  with 


BY   DR.    KLEIN.  37 

needles  (avoiding  every  kind  of  mechanical  injury)  in  such  a 
manner  that  the  peritoneal  surface  looks  upwards :  a  drop  of 
half  per  cent,  solution  of  common  salt  is  then  placed  on  the 
under  surface  of  the  cover-glass,  which  is  cautiously  applied. 
In  such  a  preparation  we  find  places  in  which  a  bird's-eye  view 
is  obtained  of  the  cilia  in  motion,  as  well  as  others,  where,  as 
in  the  preparation  from  the  throat  of  the  frog,  we  see  the  same 
in  profile.  The  cells,  which  bear  the  cilia,  are  not  cylindrical, 
but  form  a  pavement  endothelium,  the  elements  of  which  are 
granular.  We  shall  have  occasion  to  return  to  these  cells  in 
the  description  of  the  endothelium  of  the  septum.  The  sto- 
mata  are  almost  always  guarded  by  the  cells  above  described. 
If  we  are  uncertain  of  the  direction  in  which  the  cilia  strike,  or 
if  we  wish  to  demonstrate  this  positively,  we  should  transmit 
through  the  preparation,  by  the  method  of  irrigation  described 
in  Chapter  I.,  coloring  matter,  or  some  similar  substance,  in  a 
finely  divided  state,  such  as  ground  animal  charcoal,  cinnabar,  or 
Indian  ink,  suspended  in  half  per  cent,  solution  of  common  salt. 
We  shall  then  be  able  to  recognize,  from  the  direction  in  which 
the  particles  are  driven,  the  direction  in  which  the  cilia  strike. 

Forms  of  Ciliated  Epithelium. — For  the  study  of  the 
various  forms  of  ciliated  cells,  we  remove  a  mucous  membrane 
covered  with  these  from  a  freshly-killed  animal,  and  place 
small  pieces  of  it  in  a  sherry-colored  solution  of  bichromate 
of  potash.  After  they  have  lain  in  the  liquid  for  twenty-four 
hours  or  more,  we  scrape  with  a  scalpel  from  the  free  surface 
a  little  of  the  epithelium — place  it  on  a  slide  in  a  small  drop 
of  bichromate  of  potash  solution  or  of  common  water,  reduce 
it  to  fragments  with  the  handle  of  a  needle  and  cover  it.  The 
most  suitable  objects  for  such  a  studjr  are  the  trachea  of  a 
mammal,  the  bell-shaped  extremity  of  the  Fallopian  tube  of 
the  sow,  and  the  mucous  membrane  of  the  mouth,  throat,  and 
03Sophagus  of  the  frog.  By  this  mode  of  preparation  the  cells 
are  preserved  very  perfectly.  In  the  long  conical  cells  with 
ciliated  bases  we  have  to  notice  the  granular  protoplasm  which 
composes  the  bod}',  the  bright  basal  border,  the  sharply- 
defined  ovoid  nucleus,  with  its  large  single  or  double  nucle- 
olus ;  the  long  filaments,  simple  or  divided  processes  which 
penetrate  between  the  cells  of  the  deeper  layers,  and  finally 
the  cilia  which  pass  out  from  the  central  protoplasm,  perfora- 
ting the  basal  border. 

Besides  these,  we  find  intermediate  forms  of  ciliated  cells, 
which  are  shorter  and  broader,  and  which  run  out  into  one  or 
two  short,  thick  processes;  and  varying  forms  of  spindle- 
shaped  cells,  which,  as  we  may  convince  ourselves,  in  large 
flakes  of  epithelium,  wedge  themselves,  by  means  of  processes 
of  greater  or  less  thickness,  between  the  processes  of  the 
ciliated  elements.     They  possess,  likewise,  an  ovoid  nucleus. 


38  EPITHELIUM    AND    ENDOTHELIUM. 

Finally,  there  show  themselves,  here  and  there,  long,  conical 
cells  (goblet  cells),  which,  like  the  first  mentioned,  run  into  a 
Long  process;  and,  in  the  thicker  portion  (Fig.  7«),  are  empty, 
or  contain  only  a  very  few  granules.  The  ampullate,  or  flask- 
shaped  portion  of  these  cells  is  bordered  by  a  double-con- 
tonred  membrane,  which,  at  the  basal  end.  is  open,  so  that  we 
have  before  us  only  the  empty  shell  of  the  cell  without  the 
basal  lid.  Among  a  number  of  such  cells  swimming  about, 
individuals  occur  in  which  the  open  ends  of  the  goblets  can 
be  seen,  both  obliquely  and  from  the  surface.  In  the  deeper 
and  thinner  part  of  the  cell  the  protoplasm  with  the  nucleus 
is,  in  most  cases,  still  present,  as  represented  in  the  figure. 
In  a  few  examples  part  of  the  cell  (Fig.  lb)  is  torn  off",  so  that 
an  empty  funnel  remains  behind,  in  the  extreme  apex  of  which 
a  small  bit  of  protoplasm  remains.  If  we  look  over  a  series 
of  preparations  we  shall  certainly  find  examples  in  which  the 
complete  lid.  or  a  portion  of  it,  remains  attached  at  one  point 
only  of  the  circumference,  and  floats  freely  otherwise.  The 
appearances  show  that  these  goblet  cells  are  nothing  more 
than  products  of  changes  which  have  occurred  in  the  ordinary 
conical  ciliated  cells.  In  the  description  of  the  epithelium  of 
the  intestine  we  shall  again  have  an  opportunity  of  referring 
to  these  cells. 

Non-Ciliated  Cylindrical  Epithelium. — For  the  in- 
vestigation of  this  form  we  use  the  epithelium  of  the  papilla' 
of  the  tongue  of  the  frog,  and  that  of  the  intestinal  canal  of  a 
mammal,  either  in  the  fresh  condition  or  with  the  aid  of  re- 
agents. From  the  dorsal  surface  of  the  frog's  tongue  a  minute 
portion  is  snipped  with  curved  scissors,  transferred  b}-  means 
of  a  needle  from  the  scissors  on  to  a  glass  slide,  and  then, 
either  covered  without  addition,  the  glass  being  pressed  lightly 
down,  or  mounted  in  a  drop  of  serum,  or  of  half  per  cent,  solu- 
tion of  common  salt.  The  specimen  must  be  examined  with 
high  powers  (as,  e.  (/.,  Hartnack's  Xo  10  immersion).  We  see 
the  numerous,  thin,  conical  papilla?,  both  from  above  and  in 
profile  ;  the  latter  especially  at  the  borders  of  the  preparation. 
A  papilla  seen  in  profile  exhibits  on  its  surface  a  beautiful 
mosaic  of  pale  cells,  composed  of  finely  granular  protoplasm, 
marked  off  by  sharp  clear-shining  lines  of  interstitial  substance. 
If  we  fix  our  attention  upon  the  borders  and  apices  of  the 
papilla?,  we  may  convince  ourselves  that  the  mosaic  is  only  the 
surface  view  of  the  conical  or  cylindrical  cells,  which  cover  and 
surround  the  papilla?.  Here  and  there  we  may  easily  perceive 
that  these  cells  are  coarsely  granular,  and  that  each  contains  a 
clear  oval  nucleus.  Such  coarsely-granular  cells  increase  in 
number  after  the  preparation  has  been  mounted  some  time. 
W  may  mention  that  the  cylindrical  cells  around  the  bases  of 
the  papilla1  are  generally  ciliated. 


BY   DR.    KLEIN.  39 

Epithelium  of  Villi  of  Intestine. — In  the  rabbit  we 
proceed  as  follows:  The  animal  is  killed,  the  small  intestine 
immediately  opened,  and  from  the  borders  (which  then  cnrl 
outwards)  we  remove  a  small  portion  with  curved  scissors  as 
in  the  previous  case.  This  is  to  be  covered  with  the  mucous 
surface  upwards.  The  villi  seen  exhibit,  on  their  surfaces,  a 
regular  mosaic  of  epithelium  ;  at  their  borders,  where  the  epi- 
thelium is  in  profile,  it  is  seen  to  consist  of  regular  cylindrical 
cells.  If  the  observation  of  the  mosaic  is  continued  for  some 
time,  granular  spherical  bodies  come  into  view  ;  at  first  singly, 
but  afterwards  in  numbers,  which  are  raised  above  the  general 
surface  of  the  cells,  as  may  be  learnt  by  using  the  fine  adjust- 
ment. These  spherical  bodies  have  escaped  from  the  cylindri- 
cal cells.  We  shall  see  that  it  is  by  this  means  that  the  goblet 
cells  already  mentioned  are  produced.  The  epithelial  cells  on 
the  borders  of  the  villi  display  distinctly  the  broad,  finely- 
striated  border,  which  spreads  over  their  ends  like  a  cuticle. 
Equally  instructive  specimens  may  be  obtained  from  the  intes- 
tine of  the  cat,  dog,  guineapig,  rat  or  hedgehog.  The  epithe- 
lium of  the  villi  ma}'  be  as  successfully  studied,  while  still 
attached,  in  a  preparation,  mounted  in  serum,  or  half  per  cent, 
solution  of  common  salt.  For  more  prolonged  examination, 
especially  if  we  wish  to  study  isolated  cells,  we  put  a  piece  of 
intestine,  cut  from  the  rabbit,  dog,  or  cat,  into  a  sherry-yellow 
solution  of  bichromate  of  potash,  allow  it  to  remain  there  for 
one  or  more  days,  and  make  our  preparation  in  the  manner  al- 
ready described  with  regard  to  the  trachea.  In  such  speci- 
mens we  find  not  only  numerous  isolated  cells,  but  also  com- 
plete villi,  and  parts  of  the  same,  on  which  the  epithelium, 
when  its  surface  is  viewed,  resembles,  as  in  the  fresh  prepara- 
tion, a  pavement  of  granular  cells,  each  of  which  contains  a 
relatively  large,  sharply-bordered,  and  apparently  round  nu- 
cleus. The  lines  of  interstitial  substance  are  sharp  and  dark. 
At  the  edges  of  each  villus  the  epithelial  cells  are  cylindrical, 
with  finely-striated  border.  Each  cell  consists  of  granular 
protoplasm,  and  contains  a  sharply-defined  nucleus,  in  which  a 
distinct  nucleolus  is  to  be  seen. 

If  we  examine  attentively  the  surface  of  a  villus,  or  of  a  por- 
tion of  villus  (especially  in  a  preparation  from  the  intestine  of 
the  dog  or  cat,  which  has  been  allowed  to  remain  in  a  solution 
of  bichromate  of  potash),  we  shall  find,  between  the  mosaic  of 
granular  cells,  roundish  structures,  either  single  or  in  small 
groups,  and  with  a  diameter  greater  than  that  of  the  cells  of  the 
mosaic  ;  these  are  quite  clear  in  the  centre,  have  a  doubly-con- 
toured membrane,  and  give  the  impression  of  vesicular'bodies. 
If  we  search  on  the  borders  of  the  villi  for  a  structure  in  profile 
Corresponding  to  this  surface  appearance,  we  find  between  the 
cylindrical  cells,  which  are  full  of  protoplasm,  bodies  of  a  bell- 


40  EPITHELIUM    AND    ENDOTHELIUM. 

or  goblet-shape,  containing  in  the  part  which  is  next  the  tissue 
of  the  villus,  a  hit  of  protoplasm  of  variable  size,  refracting 
light  strongly;  within  this  is  included  a  compressed,  nuclear 

body.  Amongst  the  isolated  cells,  also,  we  meet  with  nume- 
rous goblet-shaped  ones,  which  may  be  examined  in  various 
positions.  These  cells  are  most  numerous  in  the  intestines  of 
the  dog  and  cat,  in  which  it  often  occurs  in  preparations  which 
have  been  kept  in  dilute  chromic  acid,  or  bichromate,  that  the 
epithelium  is  almost  entirely  transformed  into  goblet  cells.  The 
facts  show  that  they  are  transformations  of  cylindrical  epithe- 
lial cells,  and  that  they  may  either  be  produced  spontaneously, 
or,  as  more  commonly  happens,  may  be  the  product  of  certain 
reagents. 

Pavement  Epithelium. — This  variety  is  well  known  to 
occur,  chiefly  as  laminated  epithelium,  in  the  conjunctiva 
corner,  mucosa  of  mouth  and  pharynx  of  mammals,  and  in 
the  skin.  In  the  urinary  bladder  of  mammalia  the  epithelium 
is  not  purely  pavement,  but  is  mixed  with,  and  shades  off  into, 
the  cylindrical  variety.  We  accordingly  call  it  "transitional." 
The  epithelium  of  the  frog's  urinary  bladder  is  a  single  layer 
of  pavement  epithelium.  That  of  the  serous  membranes,  of 
the  membrana  Descemeti,  and  of  the  iris,  consists  mostly  of  a 
single  layer  of  flat  cells. 

Fresh  specimens  of  the  epithelium  of  the  mouth  may  be  pre- 
pared either  with  indifferent  reagents  or  with  very  dilute  solu- 
tion of  bichromate  of  potash ;  but,  if  we  wish  to  stud}'  the 
relation  of  the  various  layers  of  the  laminated  epithelium  to 
each  other,  it  is  needful  to  make  vertical  sections  through  the 
superficial  layers  of  the  mucous  membrane.  To  study  the 
forms  of  the  various  cells  of  the  separate  layers,  we  ma}'  ob- 
tain a  thin  shred  from  the  surface  of  the  tongue  or  gums  of  a 
mammal  by  energetically  scraping  it  with  a  scalpel.  What  is 
removed  is  broken  up  with  needles,  and  covered  either  in  half 
per  cent,  solution  of  common  salt,  or,  what  is  quite  as  good,  a 
very  weak  solution  of  bichromate  of  potash.  In  the  surface 
layers  of  the  epithelium,  we  find  flat  tablet-shaped  cells,  with 
small,  oblong,  strongly  refracting  nuclei;  the  borders  of  these 
cells  are  sharp  and  doubly-contoured.  Their  substance  is 
mostly  clear,  containing  only  a  few  granules,  generally  situated 
in  the  immediate  neighborhood  of  the  nucleus.  Their  surface 
is  generally  beset  with  irregular  folds  and  furrows.  If  one  of 
these  cells  is  seen  edgewise  it  appears  spindle-shaped,  because 
the  thickness  of  the  nucleus  is  greater  than  that  of  the  cell. 
Besides  these  we  find  smaller  polyhedric  pavement  cells,  which 
consist  of  a  nearly  uniformly  granular  protoplasm,  and  possess 
one,  or  very  rarely  two,  roundish,  clear,  and  sharply-define'd 
nuclei,  with  one  or  two  large  granules — i.  «.,  nucleoli — within 
them.     Finally,  if  we  have  scraped  very  energetically  with  the 


BY    DR.    KLEIN.  41 

scalpel,  we  meet  with  cells  corresponding  to  the  deepest  layers, 
which  possess  more  of  a  cylindrical  form,  and  contain  an 
oblong  nucleus.  Similar  results  may  be  obtained  if  we  mace- 
rate a  portion  of  the  mucous  membrane  in  bichromate  of  pot- 
ash solution. 

To  study  the  epithelium  of  the  cornea  in  the  fresh  condition 
we  proceed  in  a  somewhat  similar  wa}\  A  frog  is  held  by  an 
assistant,  its  nictitating  membrane  drawn  down,  and  from  the 
anterior  corneal  surface  a  thin  la3'er  is  scraped  with  a  lancet- 
shaped,  or  a  cataract  knife;  the  fragment  removed  is  then 
broken  up  and  covered  in  aqueous  humor,  or  in  half  per  cent, 
solution  of  common  salt.  Here  we  find  not  only  isolated  cells, 
but  connected  masses  of  epithelium  arranged  in  layers.  By 
means  of  the  fine  adjustment  the  individual  cells  of  these  layers 
may  be  studied  ;  but  we  shall  not  at  present  occupy  ourselves 
further  either  with  the  epithelium  of  the  anterior  corneal  sur- 
face, or  with  the  membrana  Bescemeti,  since  they  will  be  fully 
described  when  we  treat  of  the  cornea. 

The  epithelium  of  the  skin  (epidermis),  and  especially  of  the 
elements  of  the  stratum  corneum,  may  be  readily  brought  under 
investigation  as  follows  :  A  small  shred  is  raised  from  either 
the  back,  or  palm  of  the  hand,  and  covered  in  water ;  reagents 
which  act  upon  horny  structures,  as,  e.g., dilute  and  concentrated 
acids  and  alkalies,  may  then  be  added.  For  the  study  of  the 
cells  of  the  Bete  Malpighii,  or  portion  of  the  epidermis  which 
lies  upon  the  corium,  or  true  skin,  the  pointed  condylomata  so 
frequentl}r  met  with,  are  peculiarly  suitable.  Cancroid  tumors 
are  equally  to  be  recommended.  We  place  these  structures  in  a 
sherry-colored  solution  of  bichromate  of  potash,  and  let  them 
macerate  ttiere  for  several  days.  At  the  end  of  this  time  we 
scrape  off  a  small  portion  of  the  epithelium  with  a  scalpel, 
transfer  it  to  a  drop  of  water  or  bichromate  solution  on  a  slide, 
break  it  up  with  a  needle-handle,  and  apply  the  cover-glass  as 
usual.  In  such  preparations  we  meet  with  very  striking  forms 
of  the  so-called  ridged  cells,  i.  e.,  polyhedric  cells  whose  surfaces 
are  covered  with  ridges  and  intermediate  furrows,  and  whose 
borders  therefore,  when  seen  in  profile,  appear  as  if  serrated. 
Wherever  two  such  surfaces  are  applied  to  each  other,  the 
ridges  of  the  one  fit  into  the  furrows  of  the  other,  the  line  of 
adaptation  being  a  zigzag  one.  The  granular  protoplasm  of 
the  individual  cells,  the  sharply-bordered,  ovoid,  single  or  double 
nuclei,  which  sometimes  lie  in  a  vacuole  in  the  protoplasm,  and 
the  nucleoli  are  clearly  seen.  Very  interesting  are  the  nume- 
rous cells  in  various  stages  of  division.  These  are  represented 
by  the  following  forms:  1.  Ceils  containing  a  single  nucleus 
constricted  into  an  hour-glass  shape,  with  two  nucleoli.  2. 
Cells  which  possess  two  nuclei  lying  quite  close  to  each  other, 
each  with  a  nucleolus.     3.  Cells  with  two  nuclei  lying  at  a 


42  EPITHELIUM    AND    ENDOTHELIUM. 

distance  from  each  other.  Amongst  those  of  the  first  form, 
some  possess  a  shallow  constriction  ;  in  some  the  constricting 
furrow  is  so  deep,  that  the  two  portions  of  the  cell  are  con- 
nected by  a  short  bridge,  which  in  others  is  reduced  to  a  slender 
filament.  The  division  of  the  nucleus  is  not  always  into  two; 
it  is  not  uncommon  to  find  cellswhose  nucleus  is  rosette-shaped. 
Further,  we  meet  with  numerous  huge,  flat  cells,  belonging  to 
the  most  superficial  layers,  in  whose  interior  is  a  vacuole  of 
variable  size,  and  shut  up  in  this  a  young  brood  of  from  two 
or  three,  to  eight  or  ten  cells.  This  variety  of  proliferation  is 
known  as  endogenous. 

Epithelium  of  the  Bladder. — As  we  have  already  re- 
marked, the  epithelium  of  the  mucous  membrane  of  the 
urinary  bladder  of  mammals  is  laminated  and  transitional.  A 
thin  shred  from  the  internal  surface  of  the  urinary  bladder 
of  the  rabbit,  guineapig,  dog,  or  cat,  in  the  fresh  state,  may 
be  covered  in  half  per  cent,  solution  of  common  salt  in  water, 
or  in  a  bichromate  solution.  If  the  bladder  has  been  kept  from 
twenty-four  to  forty-eight  hours  in  the  latter  liquid,  specimens 
are  obtained  in  which  the  following  appearances  may  be  ob- 
served: Firstly,  large  pavement  cells,  bounded  by  a  double 
contour,  and  consisting  of  a  uniformly  granular  protoplasm 
which  contains  from  two  to  five  clear  vesicular  nuclei,  each 
with  a  double  contour,  and  possessing  a  large,  shining  nucleo- 
lus. In  these  pavement  cells  we  see  that,  as  a  rule,  only  one 
of  the  surfaces  is  even ;  that,  namely,  which  corresponds  to 
the  free  surface  of  the  mucous  membrane.  Of  this  we  may 
convince  ourselves  by  examination  of  connected  masses  of 
epithelium  or  of  vertical  sections.  The  deep  surface  of  each 
cell  is  marked  by  depressions  with  prominent  ridges  between 
them,  and  is  that  by  which  it  is  in  contact  with  the  club- 
shaped  or  conical  cells  of  the  subjacent  layer,  so  that  the 
rounded  summits  of  the  latter  fit  into  the  depressions  of  the 
former.  The  cells  of  the  second  layer  consist  of  a  uniformly 
granular  protoplasm,  have  a  double  contour  membrane,  and 
each  contains  an  oval  vesicular  nucleus,  and  within  this  a 
shining  nucleolus.  They  possess  simple  or  divided  processes 
of  varying  length  and  thickness.  Among  tliem  there  are 
spindle-shaped  cells  which  insinuate  themselves  between  the 
processes  of  the  former  layer. 

To  study  the  single  layer  of  epithelium  of  the  urinary 
bladder  of  the  frog,  consisting  as  it  does  of  large  granular 
cells,  we  spread  upon  a  slide  a  portion  of  this  organ  with  the 
free  surface  upwards,  and  cover  it  with  a  piece  of  thin  glass, 
on  the  under  surface  of  which  a  small  drop  of  half  per  cent, 
solution  of  common  salt  has  been  placed.  Wherever  folds 
occur  in  the  mucous  membrane  the  epithelial  cells  show  them- 


BY    BR.    KBEIN.  43 

selves  in  profile ;  where  this  is  not  the  case,  the  surface  view 
alone  is  obtained. 

The  Endothelium  of  the  Serous  Membranes.— The 
endothelium  of  the  serous  membranes,  as  well  as  that  of  the 
membranes  related  to  them  (for  example,  those  which  cover 
the  posterior  surface  of  the  cornea  and  the  iris  of  mammals, 
and  the  septa  and  walls  of  the  lymph  sacks  of  amphibia),  is 
well  known  to  consist  of  flat  cells,  the  substance  of  which 
appears  homogeneous  when  fresh,  but  becomes  finety  granular 
by  the  action  of  certain  reagents.  The  nucleus  is  generally 
single,  and  occasions  a  projection  of  the  free  surface.  It  is 
usually  oval  and  clear,  and  sometimes  contains  a  nucleolus  in 
its  interior.  Some  cells  contain  two  nuclei.  By  reason  of 
the  homogeneity  of  its  protoplasm,  the  endothelium  of  the 
serous  membranes  is,  with  difficulty,  brought  into  view  in  the 
fresh  state.  In  folds,  indeed,  of  a  serous  membrane  which 
has  been  spread  out  upon  a  slide  in  a  solution  of  common  salt 
or  in  other  indifferent  reagents,  the  individual  cells  may  be 
recognized  in  profile.  Again,  on  the  omentum,  and  on  certain 
parts  of  the  pleura  of  many  animals,  there  occur  bodies 
(which  were  first  described  by  Sanderson  as  structures  re- 
sembling lymph  follicles,  and  which  we  shall  describe  at 
length  in  another  place),  the  endothelium  covering  which  may 
be  seen  in  the  fresh  state  to  consist  of  granular  cells  which 
are  polyhedral,  but  rounded  on  their  free  surfaces,  each  in- 
closing a  rounded  nucleus.  On  the  fenestrated  portion  of  the 
omentum,  also,  spots  are  met  with  where  granular  cells  of  the 
same  form  occur  in  groups,  the  elements  of  which  appear  to 
sprout  out  as  it  were  from  a  common  stem.  Cells  of  the  same 
kind  are  also  found  on  the  abdominal  surface  of  the  centrum 
tendineum  of  the  diaphragm,  over  the  structures  to  be  after- 
wards described  as  lymph  channels.  Further,  as  we  have 
already  had  occasion  cursorily  to  remark,  there  occurs,  in  the 
mesentery  and  parietal  peritoneum,  and  in  the  female  of  Bufo 
and  Rana,  on  the  septum  separating  the  cisterna  lymphatica 
magna  from  the  peritoneal  cavity,  between  the  non-ciliated, 
homogeneous,  large  and  flat  endothelial  cells,  others  which  are 
ciliated,  granular,  small,  and  polyhedral,  occuring  either 
singly  or  in  groups.  To  bring  these  into  view  we  have  simply, 
as  we  have  said,  to  remove  a  portion  of  the  membrane  in 
question  from  the  recently  killed  animal,  to  spread  it  out 
carefully  upon  a  slide  witli  a  couple  of  needles,  avoiding  all 
unnecessary  dragging,  and  to  cover  it  quickly  before  it  be- 
comes dry,  with  a  cover-glass,  on  which  a  small  drop  of 
half  per  cent,  solution  of  common  salt,  serum,  or  aqueous 
humor  has  been  placed. 

The  Silver  Method. — The  best  method,  however,  and  the 
one  most  frequently  employed  for  exhibiting  endothelium,  is 


44  EPITHELIUM    AND    ENDOTHELIUM. 

that  of  coloring  by  means  of  a  solution  of  nitrate  of  silver. 
This  method  consists  in  bathing  the  fresh  membrane,  which, 
of  course,  has  not  been  allowed  to  conic  into  contact  with 
blood  or  any  injurious  tluid,  in  a  quarter  or  half  per  cent,  so- 
lution of  nitrate  of  silver.  After  immersion  in  this  for  a  few 
minutes,  it  is  washed  out  in  ordinary  water,  which  must  be 
renewed  as  often  as  it  becomes  turbid,  and  is  then  exposed  to 
the  light  until  it  assumes  a  brownish  color.  The  portion  of 
membrane  thus  treated  is  spread  out  upon  a  glass  slide  and 
covered,  a  small  drop  of  glycerine  having  been  previously 
placed  on  the  under  surface  of  the  cover-glass.  On  superficial 
examination  a  system  of  dark  lines  is  seen,  which  bound  clear 
spaces  of  various  forms  and  sizes  corresponding  to  the  indi- 
vidual endothelial  cells.  Hefore  mounting  such  a  portion  of 
membrane  in  glycerine,  after  having  colored  it  with  silver,  Ave 
may  place  it  for  a  short  time  in  very  dilute  ammoniacal  car- 
mine solution  (to  which,  however,  two  small  drops  of  acetic 
acid  have  been  previously  added),  and  then  wash  it  in  slightly 
acidulated  water.  We  shall  then  find,  on  mounting  the  speci- 
men, that  nuclei  appear  in  the  spaces  above  mentioned  :  these 
are  sometimes  central,  but  more  often  to  one  side,  and  are  ob- 
long in  form.  According  to  the  duration  of  the  action  of  the 
carmine  solution,  and  to  its  strength,  they  are  more  or  less 
intensely  colored.  By  a  modification  of  the  silver  method  we 
may  demonstrate,  not  only  the  nuclei  and  dark  lines,  but  also 
the  cell  substance  of  the  endothelia.  This  method  always 
succeeds  with  the  endothelium  which  lines  the  lymph  sacs  of 
the  frog,  and  with  that  of  the  abdominal  side  of  the  diaphragm: 
sometimes  also  with  the  endothelium  of  other  serous  mem- 
branes. If  we  allow  the  membranes  mentioned  to  lie  for  a 
longer  time  (ten  to  fifteen  minutes)  in  a  half  per  cent,  nitrate 
of  silver  solution,  and  then  simply  wash  them  in  water,  and 
mount  them  in  glycerine  after  they  have  acquired  a  browrn 
color,  we  shall  be  able  to  recognize,  after  an  interval  of  from 
twelve  to  twenty-four  hours,  or  often  even  earlier,  the  sub- 
stance of  the  endothelial  cells  as  a  3'ellow  or  dark  brown  pre- 
cipitation surrounding  the  clear  oval  nucleus.  In  preparing 
specimens  with  silver  it  is  in  general  much  to  be  recommended 
to  mount  the  objects  in  glycerine,  as  soon  as  they  have  assumed 
a  brownish  tint,  and  not  to  leave  them  exposed  to  the  light  for 
an  unnecessarily  long  time,  otherwise  they  are  apt  to  lose  their 
beauty  and  clearness,  from  the  occurrence  of  dark  precipitates. 
In  man}'  parts  of  silver-colored  serous  membranes  a  peculiar 
arrangement  of  the  endothelium  is  observed,  which  consists  in 
the  existence  of  dark  or  clear  spaces  of  various  forms,  around 
which  the  cells  are  set  in  a  radiating  manner.  Each  of  these 
small  apertures  occurs  at  the  point  of  junction  of  three  or 
more  endothelial  cells,  the  interstitial  lines  of  which  radiate 


BY    DR.    KLEIN.  45 

from  the  aperture.  Such  an  arrangement  we  find  on  the  por- 
tions of  the  abdominal  side  of  the  diaphragm,  which  corre- 
spond to  the  so-called  lymph  channels,  on  certain  parts  of  the 
mesentery,  and  very  abundantly  in  the  pleura  and  omentum 
on  the  structures  already  mentioned  as  resembling  lymph  fol- 
licles. They  are  distinguished  by  the  name  of  stomata,  and 
are  looked  upon  as  the  recipient  openings  of  canals  which  be- 
long to  the  lymphatic  system.  In  the  case  *of  many  of  these 
cells  this  has  not  yet  been  proved ;  some  of  them  have  even 
been  regarded  as  small  endothelial  portions  of  larger  cells ; 
while  others  give  the  impression  of  being  accidental  forma- 
tions. Of  such  openings,  or  stomata,  those  that  occur  on  the 
septum  of  the  disterna  lymphatica  magna  of  the  frog  may 
serve  as  the  type.  If  we  cut  out  this  membrane  from  a  frog 
or  toad,  spread  it  out  and  mount  it  in  a  solution  of  common 
salt,  or  in  serum,  or  if  instead  we  first  color  it  in  silver  and 
then  mount  it  in  glycerine,  we  shall  find  a  proportionately 
large  number  of  roundish  or  oblong  openings  between  large 
radiating  endothelial  cells.  These  discontinuities  represent 
the  openings  to  short  canals,  which  pass  through  the  mem- 
branes and  connect  the  abdominal  cavity  with  that  of  the 
cisterna  lymphatica  magna.  These  openings  are  bordered  by 
small  granular  cells,  the  convexities  of  which  project  into 
them.  They  are  compactly  arranged  together,  and  each  pos- 
sesses a  roundish  nucleus.  If  the  spreading  out  of  the  speci- 
men has  not  been  accomplished  with  sufficient  care,  or  the 
membrane  is  too  much  shrunk,  we  miss  the  above-mentioned 
regular  openings,  and  there  appear  instead  only  groups  of 
small  roundish  cells — i.e.,  the  openings  are  collapsed,  and  the 
cells  which  line  them  have  approached  each  other,  so  as  to 
come  in  contact.  The  nature  of  the  small  bodies  which  pro- 
ject in  the  interior  of  the  stomata  has  been  disputed.  It  has 
been  believed  that  they  are  nothing  more  than  the  nuclei  of 
the  large  radiating  endothelial  cells  which  surround  them. 
But,  as  we  ma}T  convince  ourselves  both  in  fresh  and  in  silver 
preparations,  they  are  really  endothelial  cells  seen  in  profile, 
which  line  the  apertures.  In  female  frogs  and  toads  these 
cells  are  provided  with  cilia.  In  the  chapter  on  lymphatic 
vessels  we  shall  have  an  opportunity  of  making  several  addi- 
tional remarks  on  the  stomata. 

We  shall,  in  conclusion,  endeavor  to  show  that  the  lines 
which  are  brought  out  by  nitrate  of  silver  in  the  serous  mem- 
branes are  caused  by  precipitations  for  the  most  part  in  the 
albuminous  substance  which  connects  the  cells,  and  not  merely, 
as  many  authors  believe,  in  an  albuminous  fluid  which  col- 
lects between  their  surfaces.  A  serous  membrane  prepared 
from  an  animal  just  killed  may  be  spread  upon  a  cork  plate 
and  rinsed  with  one  per  cent,  solution  of  sugar,  or  with  a  very 


46  CONNECTIVE   TISSUES. 

dilute  solution  of  glycerine,  may  even  be  brushed  with  a  camel- 
hair  pencil  moistened  with  water  (of  course  not  too  vigorously), 
without  preventing  the  occurrence  of  the  silver  lines.  Again, 
in  a  section  prepared  from  :i  fresh  mucous  membrane,  with 
laminated  pavement  epithelium,  which  section  has  been  colored 
in  silver,  the  silver  lines  corresponding  to  the  borders  of  the 
individual  cells  are  distinguishable  throughout  all  the  layers. 
Farther,  silver  lines  corresponding  with  the  borders  of  the  in- 
dividual muscle  cells  are  met  with  in  anstriped  muscular  tissue 
which  has  been  colored  in  silver,  as,  e.g.,  in  the  muscular  coats 
of  arteries.  These  facts  justify  the  assumption  that  the  silver 
lines  are  caused  by  precipitations  in  the  albuminous  intersti- 
tial substance  which  bounds  and  separates  the  individual 
cells. 


CHAPTER  III. 

CONNECTIVE  TISSUES. 

Under  this  heading  we  include  the  fibrous  tissues,  with  the 
cellular  elements  which  they  contain,  the  elastic  tissues,  carti- 
lage, and  bone. 

Fibrous  Tissue. — Fibrous  tissue  consists  of  delicate  gela- 
tigenous  fibres,  which  are  connected  by  an  interstitial  albumi- 
nous substance.  The  fibres  form  bundles  of  various  thickness, 
which  either  have  a  parallel  arrangement,  as  in  tendons  and 
fascia? ;  or  form  a  meshwork  by  the  spliting  and  reunion  of 
neighboring  bundles,  as  in  the  omentum,  the  submucous  and 
subcutaneous  tissue;  or,  finally,  have  a  felt-like  arrangement 
in  which  the  bundles  cross  each  other,  or  twist  round  one 
another  in  the  most  complicated  manner,  as  in  the  skin  and 
mucous  membranes.  Fibrous  tissue  may  be  studied  in  the 
fresh  state,  or  after  maceration,  or  in  hardened  preparations. 
To  examine  the  tissue  in  the  fresh  state  it  is  best  to  make  a 
preparation  of  a  tendon  \>y  teasing.  A  small  tendon  (such  as, 
e.  g.,  one  of  the  extensors  of  the  toes)  having  been  cut  out  from 
a  recently  killed  frog  or  rabbit,  is  placed  from  ten  to  fifteen 
minutes  in  a  five  to  ten  per  cent,  solution  of  chloride  of  sodium, 
whereby  the  splitting  of  the  tendon  is  considerabl}7  facilitated. 

Process  of  Teasing. — In  making  preparations  by  teasing, 
the  following  practical  rules  must  be  attended  to:  A  very  small 
portion  must  be  used;  this  must  be  placed  on  the  glass  in  a 
drop  of  the  liquid  to  be  employed,  which  must  also  be  small, 
for  if  in  too  great  quantity  the  particles  teased  out,  swim  away 


BY    DR.    KLEIN.  47 

in  the  liquid,  and  lire  difficult  to  seize  upon  with  the  needle. 
On  the  other  hand  care  must  be  taken,  as  the  liquid  evaporates, 
to  add  more,  so  as  not  to  allow  the  prepn  ration  to  become  dry. 
In  the  preparation  of  tissues  which  consist  of  several  parallel 
bundles,  such  as  nerves,  tendons,  or  muscular  tissue,  our  object 
is  to  divide  the  fragments  in  the  direction  of  the  fibres  into 
smaller  and  smaller  portions.  Even  when  the  tissue  consists 
of  elements  which  tend  in  no  particular  direction,  it  is  still 
desirable  to  follow  one  direction  in  teasing — the  object  being 
best  attained  by  first  fixing  the  fragment  with  one  needle,  then 
piercing  it  with  the  other  held  in  the  opposite  direction,  and 
finally  drawing  the  two  apart.  It  is  further  noteworthy  that 
the  teasing  must  be  performed  on  the  centre  of  a  slide,  and 
limited  within  an  area  which  is  not  larger  than  the  cover-glass. 
The  drop  of  fluid  in  which  the  preparation  is  to  be  mounted 
should  be  placed  on  the  cover-glass,  which  must  then  be  in- 
verted upon  it.  As  the  liquid  evaporates  it  must  be  renewed 
from  time  to  time. 

Action  of  Acetic  Acid  on  Fibrous  Tissues. —  In  a 
teased  preparation  of  tendon  in  salt  solution,  bundles  of  very 
fine  homogeneous-looking  fibres  are  seen.  If  the  preparation 
is  irrigated  with  weak  acetic  acid  the  bundles  are  seen  to  swell 
out,  become  homogeneous,  and  completely  disappear.  If  con- 
centrated acid  is  used  the  effect  is  more  rapid. 

Areolar  Tissue. — In  a  portion  of  fresh  mesentery  (of  a 
frog  or  of  a  small  mammalian  animal)  spread  out  on  a  glass 
slide  and  mounted  in  salt  solution,  we  have  the  shining  wavy 
bundles  forming  a  felt-work.  In  the  omentum  or  pleura  of  a 
guineapig  or  of  a  cat,  prepared  in  a  similar  way,  the  arrange- 
ment is  that  of  a  meshwork.  From  each  larger  bundle  we  see 
several  smaller  ones  splitting  off,  and  then  meeting  with  simi- 
lar ones  which  are  branches  of  other  larger  bundles  in  the 
neighborhood.  (See  Fig.  8.)  According  to  the  abundance  of 
these  collateral  or  secondary  bundles,  and  the  way  in  which 
they  run,  the  meshes  vary  in  size  and  form,  being  round,  rhom- 
bic, or  oblong. 

Effect  of  Maceration. — For  the  purpose  of  macerating 
fibrous  tissue,  ten  per  cent,  solution  of  common  salt,  lime  water, 
baryta  water,  or  solution  of  permanganate  of  potash  may  be 
used.  By  all  these  reagents  the  interstitial  albuminous  sub- 
stance is  dissolved  out,  so  that  the  bundles  split  into  their  con- 
stituent fibres.  All  that  is  then  necessary  to  display  them  is 
to  prepare  a  small  fragment  with  needles.  Diluted  bichromate 
of  potash  solution  may  also  be  used,  but  its  action  is  very  slow. 

Elastic  Tissue. — Elastic  tissue  is  characterized  specially 
by  the  facts  that  the  elementary  fibres  of  which  it  consists  do 
not  swell  in  acids,  that  they  do  not  yield  gelatin  in  boiling, 
and  that  in  general  they  are  not  united  into  bundles,  but  occur 


48  CONNECTIVE    TISSUES. 

as  sharply  defined  threads  which  run  an  isolated  course,  some- 
times straight, sometimes  contorted,  or  even  spiral.  By  repeated 
bifurcations  and  fusions  of  the  branches  again  with  one  another, 
they  form  a  network.  These  facts  may  be  demonstrated  very 
advantageously  in  a  serous  membrane,  particularly  in  the  meso- 
colon of  the  rabbit,  or  in  that  part  of  the  parietal  peritoneum 
of  the  same  animal  which  lies  on  either  side  of  the  lumbar  ver- 
tebra. In  both  of  these  situations  the  elastic  fibres  are  very 
strongly  developed.  If  preparations  of  these  or  similar  mem- 
branes are  treated  with  acetic  acid,  the  bundles  of  common 
connective  tissue  disappear,  so  that  the  network  of  elastic 
fibres  becomes  prominent. 

To  show  the  elastic  fibres  of  the  ligamentum  nuchx,  the  best 
way  is  to  make  preparations  by  teasing  a  portion  of  that  of 
the  ox,  in  salt  solution,  either  in  the  fresh  condition,  or  after 
maceration  for  a  day  or  more  in  sherry-colored  solution  of 
bichromate  of  potash.  In  either  case  we  have  before  us  thick, 
solid,  shiny  cords  of  homogeneous  substance,  which  branch 
dichotomously,  uniting  by  their  branches  so  as  to  form  a  net- 
work. The  individual  fibres,  however,  run  mostly  in  one  direc- 
tion, and  are  so  close  to  one  another,  that,  on  superficial  exami- 
nation, they  exhibit  the  appearance  of  a  reticular  arrangement. 
Such  fibres  as  happen  to  be  separated  from  the  rest  are  often 
rolled  up  like  a  watch-spring. 

The  dichotomously-branching  elastic  fibres  of  the  pulmonary 
substance  can  be  shown,  either  by  teasing  fragments  of  fresh 
lung  (an  operation  which  requires  an  immense  deal  of  patience), 
or  in  sections  of  fresh  lung  hardened  by  freezing,  as  will  be 
afterwards  described.  The  elastic  so-called  fenestrated  mem- 
branes which  exist  in  the  tunica  intima  of  the  large  arteries 
may  be  demonstrated  as  follows:  A  part  of  the  aorta  of  a  rab- 
bit or  guineapig,  having  been  cut  out,  is  pinned  down  on  a  flat 
cork  with  the  internal  surface  upwards.  The  membrane  having 
been  fixed  at  a  certain  point  with  a  needle,  the  intima  is  raised 
up  close  to  the  latter  with  sharp  forceps,  and  then  shreds  as 
long  as  possible  are  stripped  off — a  process  which  requires  no 
remarkable  skill.  Any  one  possessed  of  the  requisite  dexterity 
may  then  strip  off  thin  lamella  from  the  deep  surface  of  these 
shreds  ;  these  may  be  at  once  mounted,  and  are  so  thin  that 
the  fenestrated  membrane  can  be  seen  at  the  edges  without 
further  preparation.  If  this  does  not  succeed,  the  student 
must  content  himself  with  teasing  out  the  shreds  first  obtained. 

Finally,  a  network  of  elastic  fibres  can  be  shown  very  beauti- 
fully in  the  vocal  cords  of  the  frog.  To  any  one  who  is  suffi- 
ciently acquainted  with  the  general  anatomical  relations  of  the 
parts,  it  is  not  difficult  to  remove  those  structures  even  from 
the  living  animal.  The  easiest  way  is  to  place  the  vocal  cord 
for  a  few  minutes  in  dilute  acetic  acid,  and  then  to  scrape  off 


BY    DR.    KLEIN.  49 

the  epithelium  with  a  lancet-shaped  needle— a  process  which  is 
much  facilitated  by  the  previous  steeping  in  the  acid.  The 
preparation  is  then  mounted  in  glycerin. 

Cellular  Elements  of  the  Connective  Tissue. — These 
are  either  amoeboid — i.  e.,  migratory  cells  ;  or  branched — i.  e., 
fixed  cells  ;  the  latter  being  distinguished  further  by  the  union 
of  their  branched  or  simple  processes,  so  as  to  form  networks 
of  various  densities. 

Amoeboid  Cells. — These  are  to  be  found  in  every  form  of 
connective  tissue.  Normally,  the}'  occur  only  in  small  num- 
bers, and  are  irregularly  distributed;  but,  in  inflammation, 
they  are  numerous  in  proportion  to  the  intensity  of  the  process, 
their  multiplication  being  sometimes  scarcely  observable,  while, 
at  other  times,  they  are  so  numerous  as  to  fill  up  the  tissue. 
Two  kinds  may  be  distinguished  :  the  cells  of  the  first  form 
entirely  resemble  the  colorless  blood  corpuscles — i.  e.,  they  con- 
sist of  finely  granular  protoplasm,  contain  two  or  more  nuclei, 
exhibit  amoeboid  movements,  and  are  similarly  affected  b}r  re- 
agents ;  while  those  of  the  second  form  are  large,  coarsely 
granular  cells,  which,  like  the  granular  cells  of  the  blood,  are 
characterized  by  the  rounded  contour  of  their  processes.  The 
former  are  to  be  found  in  every  connective  tissue,  but  the  latter 
are  more  common  in  the  subcutaneous  and  submucous  tissue, 
in  the  intermuscular  connective  tissue,  in  the  mesentery,  in  the 
neighborhood  of  bloodvessels,  in  the  septa  of  the  subcutaneous 
lymph  sacs  of  the  frog  or  toad,  and  in  the  neurilemma  of  the 
larger  nerve  trunks  of  the  frog.  The  two  forms  graduate  into 
each  other. 

The  method  of  studying  these  cells  in  the  living  condition 
consists  simply  in  spreading  out  thin  shreds  of  connective  tis- 
sue on  a  glass  slide,  and  mounting  them  in  indifferent  liquids. 
Where  the  integument  is  loose,  as  in  the  neck  of  mammalia,  etc., 
it  is  easy  to  effect  this,  by  first  making  a  slit  in  the  skin,  and 
then,  with  curved  scissors,  snipping  away  a  thin  lamella  of 
subcutaneous  tissue.  In  the  frog,  the  tongue  ma}'  be  drawn 
out  and  fixed  by  an  assistant,  while  the  operator  snips  out  a 
portion,  so  as  to  obtain  a  cut-surface,  from  which  a  thin  la- 
mella can  be  readily  taken,  as  above.  In  either  case  the  lamella 
must  be  spread  out,  without  loss  of  time,  and  with  as  little  dis- 
placement as  possible,  on  the  slide,  and  mounted  in  humor 
aqueus  or  fresh  serum.  Blood  corpuscles  which  exist  on  the 
surface  of  the  preparation  do  not  interfere  with  the  object,  be- 
cause the  amoeboid  cells  are  to  be  found  in  the  interstices  of 
the  clear  transparent  fibrillated  mass  of  fibrous  tissue.  It  is 
somewhat  more  difficult  to  demonstrate  the  migratory  cells  of 
the  normal  cornea.  The  method  is  as  follows:  A  frog  is  held 
by  an  assistant  in  such  a  way  that  the  bulbus  oculi  is  tense. 
The  membrana  nictitans  is  then  drawn  back,  and  the  bulb  pene- 
4 


50  CONNECTIVE   TISSUES. 

trated  with  a  cataract  knife,  just  as  in  the  operation  for  cata- 
ract, at  the  limbus  conjunctivae  next  the  inner  canthus.  The 
point  of  the  knife  is  advanced  until  it  approaches  the  limbus 
of  the  opposite  side,  without  puncturing  it,  and  is  then  carried 
outwards  and  upwards,  so  as  to  form  a  11a}),  consisting  of  the 
upper  half  of  the  cornea.  The  extreme  edge  of  the  flap  must 
then  be  seized  with  the  forceps,  while  the  lower  half  of  the 
cornea  is  cut  away  with  the  aid  of  scissors  curved  in  the  direc- 
tion of  their  edge.  The  cornea  is  next  transferred  to  a  drop 
of  humor  aqueus  (previously  obtained  by  puncturing  the  oppo- 
site eye)  and  spread  out  on  the  glass  slide  with  the  anterior 
surface  uppermost.  In  order  to  avoid  folds,  it  is  desirable 
to  make  two  or  three  radical  incisions.  The  preparation  is  now 
covered  and  inclosed  in  oil.  If  it  is  desired  to  study  the  mi- 
gratory cells  on  the  warm  stage,  the  preparation  must  of 
course  be  mounted  between  two  cover-glasses,  as  before  di- 
rected. 

If  a  cornea  is  thus  prepared  with  great  care,  nothing  is  to 
be  seen  excepting  that  a  few  pale  lines  of  interstitial  substance, 
referable  to  the  anterior  epithelium,  may  be  distinguished  where 
the  membrane  is  folded.  No  other  optical  differences  can  be 
made  out.  If  the  individual  epithelial  elements  can  be  distin- 
guished, this  affords  proof  that  the  object  has  been  injured  in 
preparation.  Notwithstanding  its  homogeneity,  it  is  possible 
(with  the  No.  10  immersion  objective  of  Hartnack)  to  find  out 
the  upper  and  under  surfaces  of  the  cornea  by  means  of  colored 
blood  corpuscles,  pigment,  granules,  or  retina-elements  which 
may  happen  to  be  in  contact  with  them.  As  time  goes  on,  the 
interstitial  lines  of  the  anterior  epithelium  come  into  view.  If 
we  then  adjust  the  microscope  so  as  to  bring  into  view  the 
most  superficial  layer  of  the  propria,  a  few  corpuscles  of  more 
or  less  irregular  form  can  be  detected,  each  of  which  consists 
of  almost  hyaline  protoplasm,  and  contains  a  nucleus  of  ir- 
regular form,  apparently  finely  granular.  If  one  of  these  cor- 
puscles is  watched  carefully,  it  is  seen  that  changes  of  form 
take  place,  both  in  the  protoplasm  and  in  the  nucleus.  The 
corpuscles  throw  out  processes  and  retract  them,  and  even  per- 
form a  certain  amount  of  locomotion.  The  nuclei  become  con- 
stricted or  compressed,  and  again  resume  their  original  form, 
to  undergo  similar  changes.  By  and  by  similar  corpuscles 
become  visible  in  the  depth  of  the  cornea.  On  the  warm  stage 
the  movements  are  naturally  more  active.  (See  Chapter 
XIY.) 

If  a  preparation  is  made  in  humor  aqueus  of  the  fresh  peri- 
toneum (particularly  the  omentum)  of  the  frog  or  of  a  mammal, 
or  of  a  septum  of  a  subcutaneous  lymph  sac  of  the  former,  in- 
numerable migratory  cells  are  seen,  especially  in  the  neighbor- 
hood of  the  vessels,  which  present  transitions  between  small 


BY    DR.    KLEIN.  51 

pale  corpuscles  and  large  granular  ones,  all  exhibiting  distinct 
amoeboid  movements.  But  the  best  place  for  observing  these 
bodies  is  the  tail  of  the  tadpole.  If  a  portion  of  the  tail  is 
taken  from  the  thin  membranous  part,  and  mounted  in  half 
per  cent,  salt  solution,  migratory  cells  are  to  be  found  every- 
where, consisting  of  finely  granular  protoplasm,  and  displaying 
extreme^  active  movements. 

With  reference  to  the  g?-anular  corpuscles  it  is  not  necessary 
to  add  much  to  what  has  already  been  said.  Among  the  best 
examples  are  certain  coarsely  granular  elements,  which  occur 
in  the  intermuscular  connective  tissue  of  the  frog.  If  the 
transparent  membrane  which  separates  the  muscles  of  the  thigh 
of  the  frog  is  spread  out  and  examined  in  an  indifferent  liquid, 
it  is  found  that,besides  active  migrator}7  cells,  there  are  coarsely 
granular  elements  possessing  oblong  nuclei  of  the  most  various 
forms,  which  move  very  sluggishly.  Perfectly  similar  bodies 
occur  in  the  sheaths  of  large  nerves  of  the  frog.  Another 
situation  for  studying  these  cells  in  great  numbers  is  the  tongue 
of  the  same  animal.  A  living  frog  having  been  secured  in  the 
supine  position,  its  mouth  is  opened  and  the  tongue  is  drawn 
out  by  its  two  cornua.  Thin  shreds  are  then  snipped  from  the 
substance  of  the  organ  (the  epithelium  having  been  first  re- 
moved in  the  same  way)  and  covered  in  fresh  serum.  In  a 
preparation  thus  made,  an  immense  number  of  large  coarsely 
granular  cells  appear,  presenting  the  most  grotesque  forms. 
(See  Fig.  9.) 

Branched  Cells  (Connective  Tissue  Corpuscles). — 
These  bodies  are  flattened  cells,  consisting  of  finely  granular 
protoplasm:  each  contains  a  nucleus,  which  is  also,  for  the 
most  part,  flattened  and  oblong.  The}7  possess  a  greater  or 
less  number  of  processes  ;  and  b}r  these,  which  are  sometimes 
branched,  sometimes  single,  they  are  in  continuity  with  each 
other,  so  as  to  form  a  network.  In  some  connective  tissues 
the  processes  exhibit  a  more  or  less  regular  relation  to  the 
body  of  the  corpuscles  ;  in  others,  they  are  so  short  that  the 
corpuscles  are  almost  in  contact  with  each  other,  being  sepa- 
rated by  scarcely  any  interstitial  substance.  In  preparations 
made  in  the  way  already  recommended  for  the  demonstration 
of  amoeboid  cells  of  the  subcutaneous  connective  tissue  of  the 
rabbit,  bodies  are  also  found  which  are  distinguished  from  the 
others  by  their  very  irregular  placoid  form,  greater  size,  and 
hyaline  appearance,  as  well  as  by  the  possession  of  oblong 
nuclei.  These  cells  contain  very  few  granules,  and  those 
mostly  in  the  neighborhood  of  the  nucleus.  At  first  sight 
these  placoids  seem  to  have  only  short  projections,  but,  under 
high  powers,  they  are  found  to  possess  numerous  long  hyaline 
radiating  processes. 


52  CONNECTIVE   TISSUES. 

Fixed  Corpuscles  of  the  Cornea.— In  a  cornea  prepared 
in  the  manner  previously  described,  it  is  possible  to  recognize 
the  network  of  pale  branched  corpuscles  at  all  depths,  after 
some  time  has  elapsed.  The}'  ma}',  however,  be  more  distinctly 
shown  with  the  aid  of  certain  reagents.  p;irticularl3r  wood 
vinegar,  nitrate  of  silver,  chloride  of  gold,  and  some  other 
metallic  salts.  Of  these,  the  first  is  now  laid  aside  in  favor  of 
the  others.  In  preparations  obtained  by  stripping  off  shreds  of 
a  cornea  (of  the  rabbit  or  frog),  which  has  been  macerated  for 
twenty-four  hours  in  wood  vinegar,  the  corpuscles  are  seen  as 
large  flattened  cells,  consisting  of  granulous  protoplasm,  com- 
municating with  one  another  by  processes.  If  vertical  sections 
are  made  of  such  a  cornea,  the  cells  seem  to  be  spindle-shaped ; 
but,  if  the  section  is  made  obliquely,  it  is  found  that  the  cor- 
puscles appear  the  more  flattened  and  the  more  branched,  the 
greater  the  obliquity  of  the  section.  This  fact  proves  that  the 
corpuscles  are  flattened  in  planes  parallel  to  the  surface,  and 
that  the  processes  also  stretch  out  in  similar  planes. 

Treatment  of  the  Cornea  with  Nitrate  of  Silver. — 
Nitrate  of  silver  is  used  both  in  substance  and  in  solution.  In 
substance  it  may  be  employed  in  two  ways:  a.  The  centre  of 
the  cornea  of  a  frog,  which  is  held  by  an  assistant  in  the 
manner  previously  described,  is  firmly  cauterized  with  a  pointed 
stick  of  lunar  caustic.  One  or  two  drops  of  salt  solution  are 
then  allowed  to  flow  over  the  cornea  to  decompose  the  excess 
of  nitrate  of  silver.  About  an  hour  after  the  cauterization, 
the  cornea  is  excised  in  the  manner  directed  in  p.  49,  washed 
in  water  for  several  minutes,  and  the  surface  of  the  slough 
cleansed  by  pencilling  it  lightly  under  water.  In  the  case  of 
the  frog's  cornea,  the  central  cauterized  part  may  be  cut  out 
and  mounted  in  gbycerin  at  once;  but  the  rabbit's  cornea  is  so 
thick  that  it  is  necessary  to  split  it  into  layers,  with  the  help 
of  fine  pointed  forceps.  If  the  preparation  has  been  exposed 
to  daylight,  clear  spaces  are  seen  on  a  brown,  yellow,  or  dark 
ground,  which  communicate  with  one  another  by  clear  channels, 
either  branched  or  single.  These  correspond  in  form  and 
configuration  with  the  network  of  corpuscles  above  described. 
This  signifies  that  we  have  before  us,  as  will  be  more  com- 
pletely shown  afterwards,  the  spaces  which  the  coi'puscles 
occupy.  This  network  of  clear  spaces  represents  the  canalicular 
system  (Saftcan'dlchen  System)  of  the  cornea:  it  must  not  be 
confused  with  Bowman's  tubes,  h.  The  second  method  of  ap- 
plying the  nitrate  of  silver  in  substance  has  the  advantage 
that  it  shows  the  canalicular  system  in  all  parts  of  the  cornea. 
It  consists  in  first  scraping  the  cornea  of  a  living  frog  or  small 
mammal  with  a  sharp  cataract  knife,  so  as  to  remove  the  epi- 
thelium completely.  After  a  little  practise,  and  provided  the 
bulb  is  properly  fixed  by  an  assistant,  it  is  not  difficult  to  per- 


BY   DR.   KLEIN.  53 

form  this  operation  without  injuring  the  substance  of  the  cornea. 
Thereupon  the  caustic  is  two  or  three  times  lightly  rubbed  over 
the  whole  surface,  after  which  the  eye  is,  washed  with  saline 
solution,  and  the  animal  is  left  to  itself  for  twenty  or  thirty 
minutes.  The  cornea  is  then  excised,  washed  in  ordinary 
water  for  several  minutes,  and  pencilled  with  a  camel-hair 
brush.  The  mode  of  preparation  is  as  before,  care  being  taken 
to  make  one  or  two  radial  incisions,  in  order  that  the  mem- 
brane may  lie  flat  on  the  glass  surface.  After  the  preparation 
has  been  exposed  for  a  few  hours,  the  contrast  between  the 
spaces  and  the  yellowish-brown  interstitial  substance  becomes 
very  obvious. 

[The  endothelium  of  Descemet's  membrane,  with  its  dark 
interstitial  lines,  brownish-yellow  cell  substance,  and  clear 
ovoid  or  lobed  nuclei,  is  well  seen.  It  is  to  be  noted  that  all 
preparations  of  this  kind  must  be  kept  in  the  dark.] 

Similar  results  are  obtained  by  the  use  of  the  nitrate  of 
silver  in  solution.  With  this  view  the  epithelium  is  either 
pencilled  off  from  the  anterior  surface  with  warm  water,  or 
scraped  off  as  above  described.  The  cornea  is  then  imme- 
diately excised  and  immersed  for  fifteen  or  twenty  minutes  in 
a  half  to  one  per  cent,  solution.  It  is  then  washed  and  pre- 
pared as  above.  If,  however,  after  washing  the  preparation 
for  a  very  short  time,  it  is  transferred  to  a  ten  per  cent,  solu- 
tion of  chloride  of  sodium  for  five  or  ten  minutes,  and  is  then 
again  washed  in  ordinary  water  and  mounted  in  glycerin,  the 
appearance  is  very  different.  We  have  before  us  in  most  parts 
the  canalicular  system  marked  out  by  a  dark  precipitate,  while 
the  interstitial  substance  remains  almost  clear.  In  other  parts 
there  are  gradations  of  staining  between  this  appearance  and 
the  negative  staining  obtained  by  the  ordinary  method. 

Preparation  of  the  Cornea  with  Chloride  of  Gold. 
— The  fresh  cornea  of  a  frog  or  mammal  is  placed  in  as  much 
half  per  cent,  solution  of  pure  chloride  of  gold  as  is  sufficient 
to  cover  it,  and  left  immersed  until  it  acquires  a  straw-yellow 
color — i.  e.,  at  most  thirty  minutes.  Thereupon  it  is  trans- 
ferred to  distilled  water,  or  water  slightly  acidulated.  The 
preparation  passes  through  pale  gray,  then  dark  gray,  violet 
gray,  violet  and  reddish,  to  dark  red — the  time  required  for  the 
production  of  the  last-mentioned  color  differing,  cxteris  paribus, 
according  to  the  time  during  which  it  was  immersed,  and  the  in- 
tensity of  the  light.  In  the  height  of  summer,  twenty-four 
hours,  or  oven  less  time,  is  sufficient ;  but  in  winter  several  days 
are  required,  in  which  case  it  is  preferable  to  use  distilled,  rather 
than  acidulated,  water,  because  the  latter  is  apt  to  produce  too 
much  swelling  of  the  preparation.  From  a  darkly  colored 
cornea  bo  prepared,  the  anterior  epithelium  is  removed  by  strip- 
ping it  off  from  the  cumulus  conjunctivae  inwards,  with  the  aid 


54  CONNECTIVE    TISSUES. 

of  a  sharp  pointed  forceps.  If  that  of  a  frog,  the  cornea  may 
tlien  lie  mounted  in  glycerin  without  .farther  preparation.  The 
rabbit's  cornea  must  be  prepared  as  before  directed.  In  this 
way  one  of  the  most  beautiful  preparations  in  the  whole  range 
of  histology  is  obtained.  The  bodies  and  processes  of  the  cor- 
puscles are  seen  to  consist  of  a  more  or  less  granular  proto- 
plasm of  various  shades  of  violet.  Each  corpuscle  contains  a 
flattened  oblong,  well-defined  nucleus,  which  is  of  a  violet 
color,  and  incloses  one  or  two  large,  round,  dark  colored  nu- 
cleoli. (Fig.  10.)  Corneas  stained  with  chloride  of  gold  may 
also  be  advantageously  studied  by  vertical  sections,  and  by 
sections  parallel  with  the  surface  :  from  such  sections  it  is  easy 
for  any  one  to  satisfy  himself  that  the  structures  seen  actually 
exist  as  such,  and  are  not  the  products  of  the  mode  of  prepara- 
tion. It  is,  however,  necessary  to  demonstrate  that  the  cana- 
licular network  which  we  see  with  such  distinctness  in  silver 
preparations,  corresponds  to  and  coincides  with  the  network 
of  branched  corpuscles  displayed  in  gold  preparations,  in  such 
a  way  as  to  make  it  certain  that  the  latter  lit  into  and  fill 
out  the  former.  There  are  two  modes  of  proof:  a.  A  frog's 
cornea  is  prepared  and  mounted,  lege  aiiis,  on  the  glass  slide 
(Fig.  6),  and  is  then  examined  with  a  No.  10  immersion,  objec- 
tive, while  an  induced  current  of  moderate  strength  is  caused 
to  act  upon  it.  After  the  excitation,  the  system  of  branched 
corpuscles  becomes  distinguishable,  and  each  is  seen  to  be 
surrounded  with  a  clear  margin.  After  a  time  this  appearance 
is  lost,  but  can  be  reproduced  b}T  repeating  the  excitation.  It 
admits  of  but  one  interpretation,  viz.,  that  the  protoplasm 
contracts,  under  the  excitation,  in  such  a  wa}r  as  no  longer  to 
fill  out  the  space  in  which  it  is  contained — again  occup3'ing  it 
as  soon  as  the  contraction  ceases,  b.  A  rabbit's  cornea  is 
gently  rubbed  with  caustic  until  the  epithelium  is  removed  as 
a  slough.  After  from  twenty  to  thirty  minutes  a  few  drops  of 
concentrated  solution  of  chloride  of  gold  are  placed  on  the 
cornea.  The  eye  is  left  to  itself  for  fifteen  or  twenty  minutes, 
after  which  time  the  cornea  is  shaved  off  with  a  razor,  and 
steeped  for  twenty-four  hours  in  water  feebly  acidulated  with 
acetic  acid.  It  is  then  not  difficult  to  prepare  from  the  parch- 
ment-like cornea,  with  sharp  forceps,  thin  lamellse  ;  or  to  make 
thin  sections,  in  planes  parallel  with  the  surface,  with  a  razor. 
In  preparations  of  either  kind  mounted  in  glycerin,  even  when 
examined  with  the  naked  eye,  three  different  colors  may  be  dis- 
tinguished. There  are  patches  of  gray  and  others  of  violet: 
and  these  two  are  separated  from  each  other  by  intermediate 
regions  of  a  dull  violet-red.  Under  the  microscope  the  gray 
parts  exhibit  the  characteristic  appearance  of  silver  prepara- 
tions— a  clear  canalicular  sj-stem  on  a  yellowish-brown  inter- 
stitial substance.     In  the  violet  parts  the  canalicular  S3-stem  is 


BY    DK.    KLEIN.  55 

also  clear,  but  the  interstitial  substance  is  violet ;  whereas  in 
the  dull  red  parts,  there  are  bluish  or  dull  red  corpuscles  on  a 
clear  ground.  Both  in  the  first  and  in  the  second,  there  are 
transitions  to  the  intermediate  parts,  i.  e.,  the  nearer  the  part 
observed  is  to  the  edge  of  the  dull  violet-red  parts,  the  more 
possible  is  it  to  make  out  that  the  network  of  protoplasm 
occupies  the  canalicular  system.  It  is  alwa}rs  possible  to  find 
points  where  the  processes  of  protoplasm  stretch  from  these 
parts  into  clear  canaliculi. 

Branched  Corpuscles  of  the  Tail  of  the  Tadpole. 
— Another  object  in  which  it  is  easy  to  demonstrate  the 
branched  corpuscles  is  the  tail  of  the  tadpole.  In  this  organ, 
when  prepared  in  the  fresh  state,  as  above  directed,  a  very 
beautiful  network  of  pale  protoplasm,  in  a  hj-aline  interstitial 
substance,  may  be  demonstrated.  The  network  consists  of 
nucleated  cells,  which  communicate  with  one  another  by  den- 
dritic processes.  It  is  most  dense  near  the  edges  and  toward 
the  tip  of  the  tail.  In  order  to  obtain  preparations  of  this 
structure,  it  is  best  to  place  a  portion  of  the  organ  of  a  tad- 
pole (in  which  the  posterior  extremities  have  begun  to  sprout) 
in  half  per  cent,  solution  of  chloride  of  gold  for  from  thirty 
to  forty  minutes.  The  preparation  having  been  placed  for 
twenty-four  hours  in  distilled  water  and  exposed  to  light,  the 
epithelium  of  one  side  must  be  removed.  For  this  purpose 
the  organ  must  be  fixed  by  a  needle  in  the  middle  line  close  to 
the  cut  end  :  the  epithelium,  with  the  plexus  of  nerves  and 
bloodvessels  of  one  side,  can  be  stripped  off  with  the  fine- 
pointed  forceps  in  the  form  of  a  membrane — a  process  which 
is  much  facilitated  by  first  placing  the  preparation  for  fifteen 
minutes  in  absolute  alcohol.  The  separated  structures  are 
then  covered  in  glycerin.  Such  preparations  are  of  great 
value,  serving  not  merely  for  the  demonstration  of  the  cells 
with  which  we  are  now  concerned,  but  also,  as  will  be  seen, 
for  the  study  of  the  structure  and  development  of  the  capil- 
lary bloodvessels,  of  the  most  minute  nerve  fibres,  and  the 
relation  of  the  lymphatic  vessels  to  the  connective  tissue 
elements.  The  description  and  mode  of  demonstration  of  the 
branched  cells  of  the  serous  membranes  will  be  given  in  the 
chapter  on  the  lymphatic  system,  in  connection  with  which 
they  are  of  most  importance. 

Branched  Corpuscles  of  the  Skin. — In  order  to  de- 
monstrate the  branched  cells  of  the  cutis  (or  of  the  mucosa), 
it  is  best  to  snip  off  folds  or  ribands  from  the  fresh  structure 
with  the  curved  scissors.  These  are  placed  in  half  per  cent, 
solution  of  chloride  of  gold  until  they  acquire  a  distinctly 
yellow  tinge.  They  are  then  transferred  into  distilled  water 
until  they  are  tinged  dark  violet  and  finally  hardened  in  ordi- 
nary alcohol.     Sections  must  then  be  made  parallel  to  the 


56  CONNECTIVE   TISSUES. 

surface  and  covered  in  glycerin.  Sections  in  this  direction 
are  preferable,  because  the  branching  of  the  cells  and  their 
mode  of  communication  cannot  be  so  well  seen  in  others. 
We  shall  return  to  these  subsequently.  In  the  membrana 
nictitans  of  the  frog  there  occur  networks  of  large,  coarsely 
granulated  cells,  containing  flattened  oblong  nuclei,  and  with 
branches  which  run  for  the  most  part  parallel  with  the  surface. 
This  structure  must  be  prepared  with  chloride  of  gold  in 
exactly  the  same  way  as  the  cornea. 

Pigment  Cells. — These  are  closely  related  to  the  fixed 
cells  now  under  consideration.  They  are  more  or  less 
branched  corpuscles,  which  are  sometimes  isolated,  sometimes 
form  a  network.  They  are,  in  general,  larger  than  the  ordi- 
nary connective  tissue  corpuscles.  Each  contains  an  oblong 
clear  nucleus,  while  both  their  bodies  and  processes  are  beset 
with  pigment  granules.  In  mammalia  they  are  found,  as  is 
well  known,  especialh-  in  the  skin,  and  in  the  sclerotic,  iris, 
and  choroid.  In  the  lower  vertebrates,  e.g..  in  the  frog,  they 
are  very  numerous,  not  only  in  the  skin,  but  in  the  peritoneum, 
and  in  several  mucous  membranes.  Pigment  cells  can  be 
made  to  retract  their  pigmented  processes  when  stimulated 
either  mechanically,  chemically,  or  electrically,  as  well  as 
under  the  influence  of  light.  Let  us  examine  them  (a)  in  the 
web,  (6)  in  the  mesentery  of  the  frog,  (c)  in  the  tail  of  the 
tadpole,  and  (d)  in  the  choroid  of  a  mammal,  (a)  A  common 
frog  (B.  temporaria)  is  secured  on  a  plate  similar  to  that 
shown  in  Fig.  11,  and  the  toes  are  extended  by  ligatures  at- 
tached to  their  tips.  With  this  view,  the  hole  0  is  surrounded 
by  five  or  six  small  perforations  into  which  wooden  pins  can 
be  stuck ;  the  ends  of  the  ligatures  are  drawn  through  the 
holes  and  fastened  with  the  pins.  In  those  parts  of  the  web, 
which  appear  to  the  naked  eye  dark,  it  is  seen,  even  with  a 
linear  magnification  of  100,  that  the  pigment  cells  are  con- 
nected by  an  extraordinary  number  of  fine  dark  processes 
which  are  either  penicilliated  or  dendritic.  Often  the  distinc- 
tion between  body  and  process  is  not  marked ;  it  looks  rather 
as  if  the  whole  network  were  made  up  of  processes.  In  other 
parts,  which  are  not  so  dark  to  the  naked  eye,  groups  of 
pigment  cells  arc  found  in  which  the  bodies  are  round  or 
oblong,  and  the  processes  broader  and  less  numerous — the 
latter  being  either  in  continuity  with  those  of  neighboring 
corpuscles,  or  broken  off  abruptly  by  a  gnawed  edge.  The 
pigment  granules  do  not  extend  to  the  end  of  these  broad 
processes  ;  so  that  it  is  possible  to  see  that  the  substance  in 
which  they  are  embedded  is  hyaline. 

If  the  dark  parts  are  touched  once  or  twice  with  a  camel-hair 
pencil  (especially  if  it  has  been  dipped  in  oil  of  turpentine), 
the  processes  are  gradually  retracted,  while,  pari  pasm,  the 


BY    DR.    KLEIN.  57 

skin  becomes  visibly  paler.  On  resuming  the  observation,  after 
the  lapse  of  one  or  two  hours,  it  is  found  that  the  pigmented 
network  is  as  dense,  and  the  processes  are  as  numerous,  as  at 
the  beginning  of  the  observation.  It  is  a  remarkable  fact 
that  the  projection  of  the  processes  is  much  accelerated  by 
the  application  of  a  drop  of  croton  oil,  with  the  aid  of  a 
capillary  pipette,  to  the  irritated  part.  In  certain  places 
where  the  cells  are  not  entirely  black,  but  have  a  more  or  less 
3'ellowish-brown  color,  and  possess  only  a  few  stumpy  pro- 
cesses, these  last  undergo  spontaneous  changes  of  form  as 
regards  length  and  thickness.  When  the  web  is  irritated, 
these,  like  the  others,  retract  their  processes  altogether.  If 
the  circulation  is  arrested  by  placing  a  ligature  around  the 
leg,  the  pigment  cells  on  the  same  side  acquire  a  brighter 
color — the  dull  brownish-yellow  tint  returning  with  the  resto- 
ration of  the  circulation. 

In  the  tail  of  the  tadpole  the  pigment  cells  in  several  respects 
resemble  the  ordinary  branched  cells.  The  most  superficial 
extend  themselves  by  their  processes  between  the  epithelial 
cells.  In  the  tadpole  of  the  toad,  which  is  distinguished  from 
that  of  the  frog  b}r  the  breadth  and  shortness  of  the  tail,  they 
are  spindle-shaped,  and  form  by  their  processes  a  tolerably 
regular  lattice-work,  with  nearly  rectangular  spaces,  which  is 
uniforml}-  distributed  throughout  the  tissue  ;  immediately  un- 
derneath the  epithelium,  however,  there  are  some  cells,  the 
mode  of  branching  of  which  is  dendritic.  In  fresh  prepara- 
tions, or  in  preparations  with  chloride  of  gold,  of  the  mesen- 
tery of  the  frog,  a  greater  or  less  number  of  pigment  cells  are 
seen  in  the  immediate  neighborhood  of  the  large  bloodvessels, 
and  especially  the  arteries,  and  often  form  a  complete  sheath 
around  them.  Isolated  pigment  cells  occur  also  elsewhere  in 
the  tissue.  With  high  powers  (No.  10  immersion)  and  with 
dilute  acetic  acid,  it  is  possible  to  make  out  in  fresh  prepara- 
tions of  the  nictitating  membrane  and  mesentery  that  the 
whole  cell  is  not  pigmented,  the  pigment  being  confined  to 
certain  parts  of  the  body  and  to  the  axes  of  some  of  the  pro- 
cesses. In  mammalia,  the  most  varied  forms  of  pigment  cells 
occur  in  the  choroid  and  sclerotic,  from  the  irregularly  formed 
cells  with  slight  knob-shaped  projections  containing  coarse 
pigment  granules,  to  cells  with  regular  dendritic  branching 
and  fine  granules. 

Fat  Cells. — Fat  cells  are  distinguished  from  ordinary 
branched  connective  tissue  corpuscles  mainly  by  the  fact  that 
they  contain  drops  of  fat.  When  an  ordinary  branched  cell 
undergoes  conversion  into  a  fat  cell,  the  change  commences 
by  the  appearance  of  small  droplets  in  the  protoplasm.  By 
the  confluence  of  these  with  each  other  a  larger  drop  is  formed. 
As  this  increases,  the  protoplasm   of  the  corpuscles   is   dis- 


58  CONNECTIVE   TISSUES. 

tended  more  and  more,  until  it  forms  around  the  globule  a 
thin  investment,  in  which  lies  the  clear  oblong  nucleus.  In 
well-developed  fat  cells,  which  usually  lie  together  in  groups, 
it  is  not  possible  to  observe  processes.  They  rather  resemble 
closel}'  packed  globular  structures. 

Transition  Forms  between  Connective  Tissue 
Corpuscles  and  Fat  Cells. — If,  in  a  rabbit,  the  skin  and 
subcutaneous  tissue  are  divided  over  the  inner  (anterior)  third 
of  the  infra-orbital  edge,  and  the  thin  membrane  which  stretches 
over  the  infra-orbital  fossa  is  severed,  it  is  easy  to  remove, 
along  with  the  glandula  infraorbitalis,  a  gelatinous  hyaline 
mass.  If,  from  this  mass,  a  very  thin  portion  is  snipped  off 
and  placed  in  a  drop  of  fresh  serum  on  a  glass  slide  and 
covered,  it  is  easy  to  distinguish,  among  the  ordinary  branched 
cells,  others  which  are  larger  and  contain  globules  of  fat.  All 
transitions  may  be  seen  between  those  which  contain  one  or 
two  small  droplets  and  those  which  are  completely  distended. 
These  structures  will  be  referred  to  again,  under  another 
heading.  Fat  cells  are,  as  a  rule,  collected  in  masses  around 
bloodvessels. 

Tendon  Cells. — The  cells  of  mature  tendon  tissue  do  not 
essentially  differ  from  those  of  ordinary  connective  tissue. 
Like  them,  they  are  oblate  branched  masses  of  protoplasm, 
which  are  in  communication  with  one  another  by  their  pro- 
cesses. They  are  not,  however,  flat,  but  curve  themselves  in 
conformity  with  the  surfaces  of  the  individual  bundles  to 
which  they  are  applied.  In  order  to  study  them,  the  best 
material  is  afforded  by  the  tail-tendons  both  of  young  and  full- 
grown  rats  or  of  rabbits,  which  can  be  examined  either  in  the 
fresh  state  in  serum,  or  by  steeping  them  for  a  few  minutes  in 
silver  solution,  after  they  have  been  first  pencilled  with  a 
camel-hair  brush  dipped  in  fresh  serum.  Another  material 
which  may  be  used  is  the  centrum  tendineum  of  the  diaphragm. 
In  very  young  animals  the  caudal  tendons  present  a  peculiar 
arrangement.  If  the  tail  of  a  very  young  rat  is  amputated, 
and  the  tip  torn  asunder  from  the  cut  end,  a  great  number  of 
isolated  lengths  of  tendon  are  obtained,  of  almost  microscopic 
tenuity.  These  may  be  at  once  separated,  and  covered  in  very 
dilute  acetic  acid.  Such  a  preparation  shows,  between  the  in- 
dividual bundles,  chains  of  apparently  quadrangular  masses 
of  protoplasm,  each  containing  a  roundish  nucleus.  These 
chains  alternate  in  position  with  the  bundles.  If,  however,  a 
single  cylindrical  bundle  of  fibrils  is  separated,  it  is  seen  that 
it  possesses  an  envelope  of  granulous  protoplasm,  which  ex- 
tends along  one  side  of  the  bundle,  covering  nearly  half  of  its 
circumference  ;  in  this  envelope  nuclei  lie  arranged  in  linear 
series.  If  the  preparations  are  treated  with  stronger  acetic  v 
acid,  the  protoplasm  between  the  nuclei  exhibits  cross  lines  of 


BY    DR.    KLEIN.  59 

interstitial  substance.  Hence  it  is  evident  that  the  sheath  of 
protoplasm  with  which  nearly  the  half  of  each  individual 
bundle  is  surrounded  consists  of  a  series  of  hollow  half-cylin- 
ders with  their  ends  in  apposition.  To  preserve  the  prepara- 
tions above  referred  to,  the  fresh  tendon  should  be  placed  for 
a  very  short  time  in  acidulated  water,  until  it  begins  to  swell 
just  perceptibly  ;  it  is  then  to  be  transferred  to  half  per  cent, 
solution  of  chloride  of  gold  for  ten  or  fifteen  minutes,  and 
washed  in  distilled  water  till  it  acquires  a  rich  color,  and  then 
to  be  mounted  in  glycerin.  In  cross  sections  through  young 
tendons  of  the  rat  or  rabbit,  in  consequence  of  the  anatomical 
facts  already  stated,  the  bundles  look  as  if  they  were  contained 
in  the  meshes  of  a  network  of  protoplasm,  with  nuclei  at  the 
nodes.  Such  sections  may  be  hest  prepared  from  the  caudal 
tendons,  or  from  the  T.  Achilles  treated  with  gold  and  then 
hardened  in  common  alcohol. 

Adenoid  Tissue. — It  remains  to  describe  the  so-called 
adenoid  tissue.  By  this  term  is  understood  a  dense  reticulum 
of  branched  cells,  the  processes  of  which  are  short  but  of  great 
delicacy.  The  younger  the  individual,  the  more  the  material 
of  which  the  reticulum  is  composed  possesses  the  character 
of  protoplasm  ;  the  older,  the  more  homogeneous  the  processes 
appear,  and  the  smaller  the  quantity  of  protoplasm  at  the  nodes, 
which  correspond  to  the  bodies  of  the  cells.  There  are  great 
differences  between  the  several  forms  of  adenoid  tissue,  which 
it  will  be  most  advantageous  to  study  in  connection  with  the 
tissues  in  which  they  are  respectively  met  with,  e.  </.,  lymphatic 
glands,  intestinal  mucosa,  etc.  The  best  objects  for  study  are 
the  mesenteric  glands  or  the  thymus  of  the  calf,  and  the  lym- 
phatic follicle  of  the  intestine  of  the  rabbit.  These  must  be 
hardened  in  Mailer's  fluid  or  in  diluted  alcohol.  As  soon  as 
the  tissue  has  become  firm  enough,  thin  sections  are  prepared, 
which  are  agitated  with  water  in  a  test  tube,  until  they  present 
the  appearance  of  a  reticular  membrane.  They  are  then  covered 
in  glycerin,  with  or  without  previous  staining.  For  more 
minute  descriptions,  see  Chapter  VI. 

Development  of  Connective  Tissue. — Fibrous  connec- 
tive tissue  is  developed  from  cells  in  two  ways,  as  follows: — 

At  a  certain  stage  of  embryonal  life,  those  organs  which,  at 
birth  and  in  the  adult  consist  of  fibrous  tissue,  are  composed 
exclusively  of  embryonal  cells.  As  development  proceeds, 
these  cells,  which  are  originally  roundish, arc  either  transformed 
into  a  network  of  branched  cells,  or  lengthened  out,  so  as  to 
form  bundles  of  spindle-shaped  cells.  At  first  both  the  bodies 
and  processes  of  the  cells,  whether  branched  or  spindle-shaped, 
consist  of  granulous  protoplasm.  The  protoplasm  subse- 
quently undergoes  a  process  of  splitting,  by  which  it  is  trans- 
formed into  fibrils.     This  change  commences  in  the  processes, 


60  CONNECTIVE    TISSUES. 

progressing  towards  the  body.  The  fibrils  are  united  to  one 
another  by  an  interfibrillar  substance,  which,  at  first  granular, 
afterwards  becomes  homogeneous.  In  this  way  the  network  of 
branched  cells  is  transformed  into  fine  fibres,  arranged  in  a 
nicshwork  ;  while  the  spindle-shaped  cells  are  converted  into 
collections  of  fibres,  running  in  parallel  bundles.  A  third  mode 
consists  in  the  transformation  of  isolated  spindle  or  branched 
cells,  which,  according  to  the  number  of  their  simple  or  divided 
processes,  split  into  a  corresponding  number  of  bundles  of  fi- 
bres. For  the  study  of  the  process  it  is  best  to  employ  the 
umbilical  cord,  the  skin,  tendons,  or  the  mucous  membrane  of 
the  mouth  or  bladder  of  young  embryos  of  man  or  animals. 
The  parts  in  question  should  be  kept  for  some  time  in  sheriy- 
yellow  solution  of  bichromate  of  potash,  after  which  the  tissues 
may  be  prepared  by  teasing  in  a  drop  of  the  solution  or  in 
water.  It  is  also  desirable,  especialby  as  regards  tendons,  skin, 
and  mucous  membrane  of  the  bladder,  to  make  thin  sections, 
after  hardening  in  solutions  of  chromic  acid  or  chromates. — 
A  splendid  object  is  to  be  found  in  the  abundant  gelatinous 
substance  which  covers  the  internal  surface  of  the  gravid 
uterus  of  the  sow,  and  extends  from  thence  over  the  external 
surface  of  the  membranes  of  the  ovum.  If  a  very  small  por- 
tion of  this  substance  is  placed  in  salt  solution  on  a  glass 
slide,  and  covered  without  any  further  preparation,  very  re- 
markable forms  of  large  branched  or  spindle-shaped  cells  are 
seen,  which  consist  of  evenly  granular  protoplasm,  and  con- 
tain roundish  or  oblong  sharply  defined  nuclei.  The  branches 
are  often  so  large  as  to  stretch  over  the  whole  field  (Xo.  8 
Hartnack),  and  the\r  may  be  seen  to  split  out  at  their  ends 
into  sheaves  of  the  most  delicate  fibrils.  From  the  abundant 
submucous  spongy  tissue  of  the  gravid  uterus  of  the  same 
animal,  instructive  preparations  maybe  obtained  (by  stripping 
off  fine  portions  with  the  curved  scissors),  which  merely  re- 
quire to  be  spread  out  with  needles  in  salt  solution.  If  the 
preparation  is  to  be  kept,  it  may  be  placed  in  bichromate  of 
potash  and  afterwards  transferred  to  glycerin.  In  the  gela- 
tinous substance  previousby  described  as  found  in  the  infra- 
orbital fossa  of  the  rabbit,  isolated  delicate  wavy  bundles  of 
connective  tissue  occur,  which,  after  a  shorter  or  longer  course, 
is  seen  to  be  in  close  relation  with  processes  of  slender  pale 
cells  which  contain  round  nuclei. 

Hyaline  Cartilage. — For  the  study  of  hyaline  cartilage,  the 
episternum  of  the  frog  and  the  thin  expansion  of  the  shoulder- 
girdle  of  the  newt  are  good  objects.  If  the  thin  part  of  either 
of  these  is  prepared  in  half  per  cent,  saline  solution  or  in  serum, 
after  the  perichondrium  has  been  carefully  separated  with  the 
aid  of  the  sharp  forceps,  the  oblong  or  spherical  cartilage  cells 
are  seen  embedded  in  a  hyaline  or  finely  granular  matrix.     The 


BY    DR.    KLEIN.  61 

edges  of  the  cells  are  sharply  defined,  their  substance  is  clear, 
or  beset  with  a  very  few  granules,  their  nuclei  are  also  some- 
what granulous.  At  all  depths  the  intercellular  substance 
(ground  substance  or  matrix)  can  be  seen,  under  high  powers, 
to  be  divided  into  territories,  each  corresponding  to  a  cell.  So 
long  as  the  preparation  is  fresh,  most  of  the  cells  completely 
fill  the  cavities  which  they  occupy  in  the  matrix;  these  cavi- 
ties are  termed  capsules.  Only  here  and  there  can  a  clear 
space  be  distinguished  between  the  external  surface  of  the  cell 
and  the  wall  of  the  capsule.  For  the  most  part  each  cell 
contains  a  single  nucleus ;  there  are,  however,  some  which 
contain  two  nuclei.  In  the  middle  part  of  the  preparation 
they  are  found  either  singl}r  and  at  equal  distances  from  each 
other,  or  in  pairs,  i.  e.,  two  in  one  capsule,  united  by  straight 
lines  of  contact.  Occasionally  two  cells  are  seen  placed 
together  in  the  same  relative  position  to  each  other  as  the  two 
inclosed  in  the  same  capsule,  but  separated  by  a  septum  of 
ground  substance,  so  that  each  is  inclosed  in  its  own  cavit}\ 
If,  for  the  indifferent  fluid,  we  substitute  distilled  water,  the 
cartilage  cells  separate  themselves  from  the  internal  surface  of 
the  cavity,  while  their  protoplasm  becomes  turbid.  If  the 
cartilage  of  the  newt  is  subjected  to  the  induction  current  in 
the  manner  already  described,  a  sudden  shrinking  of  the  cell 
results,  in  consequence  of  which  it  assumes  a  coarsely  granular 
appearance,  and  a  nodulated  form,  while  the  nucleus  becomes 
invisible.  This  condition  is  permanent,  the  cell  never  resum- 
ing its  former  appearance;  in  some,  however,  the  nucleus 
becomes  more  or  less  invisible.  A  perfectly  similar  change  is 
produced  by  the  addition  of  dilute  acetic  acid.  In  many  parts 
of  the  preparation,  especially  near  the  margin,  where  the 
cartilage  cells  are  closel}'  packed,  the  change  does  not  take 
place.  The  cells  become  more  transparent,  while  their  edges 
and  those  of  the  nuclei  become  more  sharply  defined. 

Sections  can  be  easily  made  of  cartilage  in  the  recent  state, 
and  can  then  be  examined  in  an  indifferent  liquid.  The  con- 
dyles of  the  tibia  or  femur  of  a  frog  or  mammal  may  be  used 
or  the  costal  cartilages  of  the  latter.  The  greatest  variety  is 
found  in  different  cartilages,  and  in  different  parts  of  the  same 
cartilage,  in  respect  of  the  number  and  size  of  the  cells.  For 
making  permanent  preparations  of  cartilage,  the  chloride  of 
gold  method  is  better  than  any  other.  Thin  fresh  sections  of 
cartilage  are  placed  for  ten  or  fifteen  minutes  in  a  half  per 
cent,  solution  of  chloride  of  gold,  exposed  to  light  in  distilled 
water  for  twenty-four  hours  or  more,  and  then  mounted  in 
glycerine.  The  matrix  remains  clear,  or  is  only  very  slightly 
stained  violet,  while  the  corpuscles  display  all  transitions  of 
color  between  violet,  violet-red,  and  dark  red.  The  nuclei  are 
usually   brightly    stained,    of  a    reddish    tint.      The    method 


62  CONNECTIVE    TISSUES. 

formerly  used,  which  consisted  in  staining  sections  of  cartilage, 
previously  steeped  in  chromic  acid  solution,  may  be  dispensed 
with  ;  the  plan  above  recommended  possessing  the  great  ad- 
vantage over  it,  that  the  cartilage  cells  retain  their  natural 
form  completely.  Before  leaving  hyaline  cartilage  a  word 
must  be  said  as  to  the  arrangement  of  the  cells  in  the  carti 
lages  which  occup}'  the  centre  of  the  epiphysis  of  the  tibia  ot 
the  frog.  If  the  tibia  of  a  frog  is  enucleated  from  the  knee- 
joint,  and  sections  are  made  at  right  angles  to  the  axis  of  the 
bone  through  the  condyles,  these  exhibit  concentric  layers, 
arranged  around  two  centres  corresponding  to  the  two  con- 
dyles. Proceeding  from  without  inwards,  we  have  first  articu- 
lar cartilage,  then  an  external  periosteum,  a  ring  of  bone,  an 
internal  periosteum,  and,  finall}r,  a  nucleus  of  cartilage  on 
either  side,  one  corresponding  to  each  condyle.  These  two 
cartilages  are  hyaline,  but  each  cell  constitutes  a  rigid  lamina, 
which  is  separated  from  its  neighbors  b}7-  little  or  no  matrix. 
Towards  the  diapl^ses  each  nucleus  tapers  away  gradually  ; 
and,  in  its  lower  part  there  is  a  cavity  which  is  continuous 
with  the  medullary  cavity  of  the  diaphysis,  and  contains  a 
little  liquid.  The  cells  are  here  more  separated  from  each 
other  than  they  are  towards  the  condyles ;  but,  immediately 
round  the  cavity,  they  are  more  densely  arranged,  are  roundish 
in  form,  and  look  like  lymph  corpuscles,  consisting  of  finely 
granular  protoplasm. 

In  embryonal  cartilage,  the  spindle-shaped  or  stellate  branch- 
ed cartilage  cells,  which  consist  of  granular  protoplasm,  and 
possess  spheroidal  nuclei,  are  crowded  together  in  a  hyaline 
substance,  penetrated  throughout  by  bloodvessels  (e.  g.,  in  the 
patella  or  head  of  the  femur  of  the  human  foetus).  In  the 
immediate  neighborhood  of  the  vessels  they  possess  more  or 
less  the  form  of  ordinary  cartilage  cells.  They  may  be 
prepared  for  observation  in  the  same  way  as  the  others. 

Yellow  Cartilage  differs  from  hyaline  in  the  fact  that  its 
matrix  consists  of  a  network  of  elastic  fibres,  in  which  there 
are  cavities  occupied  by  cartilage  cells,  either  isolated  or  in 
groups.  These  are  sometimes  surrounded  by  a  certain  quan- 
tity of  li3-aline  substance.  The  best  objects  for  the  study  of 
this  tissue  are  the  epiglottis  and  the  cartilage  of  the  external 
ear;  these  may  be  examined  fresh  or  in  chloride  of  gold.  In 
addition  to  these  forms,  the  so-called  2yarenchymatous  cartilage 
must  be  mentioned ;  i.  e.,  cartilage  without  matrix.  This 
occurs  in  the  embiyonal  chorda  dorsalis,  and  in  the  tendo 
Achilles  of  the  frog.  We  have  already  studied  an  example  of 
it  in  the  nucleus  cartilage  of  the  epiphyses  of  the  frog's  tibia. 

Fibro-Cartilage. — In  fibro-cartilage  the  structural  ele- 
ments of  cartilage  are  intermixed  with  gelatigenous  tissue,  as 
in  the  neighborhood  of  the  insertions  of  tendons  into  bones,  in 


BY   DR.    KLEIN.  63 

cartilages  of  the  symphyses,  etc.     The  mode  of  preparation  is 
the  same. 

Bone. — In  the  investigation  of  the  structure  of  bone,  one 
of  two  courses  may  be  followed,  according  as  we  have  in  view 
the  bony  framework,  i.  e.,  the  bone  substance  proper,  or  the 
soft  parts,  viz.,  the  periosteum,  medulla,  bloodvessels,  and 
nerves.  The  bone  substance  proper  may  be  studied  satisfac- 
torily by  means  of  thin  sections,  for  the  preparation  of  which 
the  method  is  as  follows :  A  human  long  bone,  a  vertebra,  or 
one  of  the  flat  bones  of  the  skull,  is  cleared  of  the  soft  parts 
and  dried.  The  bone  is  then  fixed  in  a  vise,  and  thin  lamella? 
are  cut  in  various  directions  with  the  aid  of  a  fine  saw.  These 
are  rubbed  down  with  moist  emery  powdered  on  a  ground- 
glass  plate,  against  which  they  are  pressed  either  with  the 
finger  alone,  or  with  a  bit  of  cork,  or  with  a  second  glass 
plate,  until  they  are  extremely  fine.  Having  been  polished 
on  a  wet  hone,  they  are  washed  in  water  and  pencilled  with  a 
camel-hair  brush,  in  order  to  get  rid  of  adhering  dirt.  They 
must  next  be  dried  and  placed  under  a  cover-glass,  either 
without  the  addition  of  any  liquid,  or  in  glycerin.  As  ex- 
amples, transverse  and  longitudinal  sections  of  a  human 
radius  may  be  taken.  In  the  one,  the  Haversian  canals  are 
seen  cut  across  ;  in  the  other,  they  appear  as  broad  channels, 
which  communicate  with  each  other  by  cross  channels,  the 
latter  running  obliquely  or  at  right  angles  to  the  former. 

The  clear  ground  substance  consists  of  lamella?  arranged 
concentrically  around  the  Haversian  canals  (primary  lamellae), 
and  secondary  lamellae,  which  run  longitudinally  in  various 
planes,  occup3'ing  the  spaces  which  are  left  between  contiguous 
systems  of  concentric  lamellae.  The  lamellae  contain  an  im- 
mense number  of  dark  cavities  (lacunae)  at  equal  distances 
from  each  other,  which,  as  longitudinal  sections  show,  are  of 
elliptical  form.  These  communicate  with  each  other  by  dark, 
somewhat  convoluted  canaliculi,  many  of  which  run  in  the 
same  layer,  but  many  also  in  such  a  direction  as  to  form  com- 
munications between  one  lamella  and  the  next.  In  dry  prepa- 
rations, the  whole  system  of  lacunae  and  canaliculi  is  filled 
with  air.  We  shall  see  afterwards  that  in  the  living  state  they 
contain  protoplasmic  branching  cells. 

A  second  method  of  preparing  bone  is  that  of  maceration. 
A  fresh  bone  is  separated  from  the  surrounding  muscles  and 
placed  in  a  large  quantity  of  a  quarter  to  half  per  cent,  solu- 
tion of  chromic  acid,  to  which  a  few  drops  of  hydrochloric  acid 
have  been  added.  The  bone  acquires  a  consistence  suitable 
for  the  preparation  of  sections  with  the  razor  in  from  a  week 
to  a  fortnight,  according  to  its  size.  If  too  soft,  it  can  be 
placed  in  diluted  alcohol.     Bones  prepared  in  this  way  may 


64  CONNECTIVE   TISSUES. 

be  used  just  as  other  tissues  hardened  in  chromic  acid  (see 
Chap.  VI.). 

For  the  study  of  the  periosteum  and  of  the  compact  bony 
substance,  i.e.,  of  its  lamellae  and  lacunae,  with  the  cells  con- 
tained in  them,  sections  of  the  long  bones  of  man  are  very 
suitable.  The  spongy  substance  can  be  best  examined  in  the 
metacarpal  and  metatarsal  bones  and  in  the  phalanges  of 
children,  or  in  those  of  rabbits  or  rats.  Very  instructive  sec- 
tions may  also  be  obtained  from  the  tibia  of  the  frog,  showing 
the  compact  substance  of  the  bone,  as  well  as  the  pigment 
cells,  fat  cells,  medullary  cells,  and  bloodvessels  of  the  marrow. 
Medullary  tissue  can  be  also  advantageously  studied  in  the 
tongue  bone  of  birds.  The  whole  tongue  is  hardened  in 
chromic  acid  solution,  after  which  sections  are  made  through 
the  posterior  part  of  the  tongue,  so  as  to  pass  through  the 
bone  in  question.  Sections  of  bone  prepared  as  above  afford 
evidence  that  the  cells  which  occupy  -the  lacunae  are  strictly 
analogous  to  the  branched  cells  of  other  connective  tissues, 
so  that  the  system  of  lacunae  and  canaliculi,  seen  in  prepara- 
tions of  dried  bone,  corresponds  entirely  with  the  system  of 
canaliculi  (Saftcan'dlchen)  seen  in  silver  preparations  of  the 
cornea,  serous  membranes,  etc.  And  it  ma}'  even  be  shown 
in  preparations  of  the  flat  bones  of  the  skull,  or  of  the  tongue 
bone  of  birds,  that  the  cells  are  not  only  in  continuity  ex- 
ternally with  those  of  the  periosteum  (which,  although  really 
branched,  look  spindle-shaped  in  section),  but  internally,  i.e., 
towards  the  medulla,  with  cells  which  are  also  more  or  less 
branched,  but  are  arranged  so  regularly  and  so  close  together 
against  the  bony  surface,  that  they  resemble  an  endothelial 
lining.  In  the  flat  bones  of  the  skull  of  human  embiyos,  the 
same  arrangement  presents  itself  with  great  distinctness — the 
cells,  which  line  the  medullary  cavities,  being  then  called 
osteoblasts. 

The  medullary  tissue  of  bone  is  rich  in  bloodvessels  and  in 
cellular  elements.  The  former  are  best  seen  in  injected  prepa- 
rations (see  Part  II.,  Chapter  VI.).  After  the  injected  part 
has  been  one  or  two  days  in  alcohol,  the  bone  must  be  freed 
from  surrounding  tissues,  and  steeped  in  chromic  acid  with 
the  addition  of  hydrochloric  acid,  as  before.  The  medullary 
cells,  which  differ  in  size  and  in  the  distinctness  of  their  granu- 
lation, may  be  examined  in  the  fresh  condition  on  the  warm 
stage,  for  the  demonstration  of  their  amoeboid  movements,  in 
the  manner  several  times  described  previously.  In  chromic 
acid  preparations,  the  individual  medullary  cells,  as  well  as 
the  fat  cells,  retain  their  form  and  aspect. 

Development  of  Bone-tissue. — For  the  study  of  the 
development  of  bony  tissue  (whether  from  cartilage  or  from 
fibrous  tissue,  as  in  the  flat  bones  of  the  skull)  the   human 


BY    DR.    KLEIN.  65 

foetus  is  best  adapted,  after  having  been  steeped  in  Miiller's 
liquid,  or  in  one-quarter  to  half  per  cent,  solution  of  chromic 
acid,  for  a  few  da}rs.  The  sections  may  be  stained  with  car- 
mine (see  Chapter  VI.).  For  studying  the  development  and 
growth  of  bone  in  the  epiphyses,  longitudinal  sections  may 
be  made  through  the  epiphysis  of  the  femur,  or  of  the  tibia,  of 
the  metacarpal  bones,  or  phalanges  of  newl}r  born  human 
foetuses,  or  of  young  rabbits. 


CHAPTER  IV. 

MUSCULAR  TISSUE. 

Section  I. — Uhstriped  Muscle. 

The  elements  of  this  tissue  are  cells — the  so-called  "  contrac- 
tile fibre-cells" — of  varying  length,  and  for  the  most  part 
spindle-shaped,  this  form  being  often  modified  by  a  flattening 
of  the  cells  where  they  come  in  contact.  Their  ends  are  either 
single  or  divided.  Their  substance  is,  in  the  fresh  state,  a  pale 
or  finely  granular  protoplasm,  sometimes  longitudinally  stri- 
ated :  in  the  thicker  part  of  the  cell  lies  an  oblong,  compressed 
nucleus,  rather  rounded  at  the  extremities  (thus  becoming 
staff-shaped),  or  pointed.  The  nucleus  contains  one  or  two 
large  shining  nucleoli :  if  single,  the  nucleolus  lies  in  the  centre 
of  the  nucleus  ;  if  double,  one  is  found  at  each  extremit}'. 
External  to  the  nucleus,  and  in  a  straight  line  with  its  longi- 
tudinal axis,  some  small  granules  may  sometimes  be  seen. 
The  unstriped  muscular  fibres  are  always  arranged  in  bundles, 
the  elements  of  which  are  separated  from  each  other  by  inter- 
stitial substance.  The  bundles  are  held  together  by  connective 
tissue,  in  which  they  lie  in  such  a  way  that  the}'  either  form 
membranes  (as  in  the  intestine)  or  meshworks  (as  in  the  blad- 
der). In  the  former  case,  the  bundles  are  parallel  and  mostly 
undivided  ;  in  the  latter,  they  run  in  various  directions,  divide 
frequently,  and  intercommunicate  with  each  other. 

The  best  materials  for  the  stud}'  of  involuntary  muscular 
fibre,  are  the  bladder  of  the  frog,  the  mesentery  of  the  newt,  the 
muscular  coats  of  the  intestines  of  the  frog  and  mammalia,  and 
arteries,  such  as  those  at  the  root  of  the  mesentery  of  the  frog. 
The}r  may  be  demonstrated  either  in  connection  or  isolated. 

To  show  their  arrangement,  a  portion  of  the  bladder  of  the 
frog  may  be  spread  on  the  glass  slide  with  the  mucous  surface 
downwards,  and  covered  in  half  per  cent,  salt  solution.  In 
5 


6Q  MUSCULAR   TISSUE. 

such  a  preparation  it  is  seen  that  a  mesh  work  is  formed  by  the 
repeated  division  of  the  bundles  of  fibres.  If  the  bit  is  soaked 
for  a  few  minutes  in  one  per  cent,  or  two  per  cent,  acetic  acid, 
the  epithelium  brushed  off  with  a  camel-hair  pencil,  and  the 
membrane  then  examined  in  water  or  glycerin,  the  individual 
elements  of  the  muscular  bundles  come  very  distinctly  into 
view ;  those  of  the  muscular  coats  of  the  arteries  can  also  be 
studied  advantageously.  The  mesentery  of  the  newt  maybe 
prepared  in  the  same  manner.  Instructive  preparations  of 
muscular  tissue  may  be  obtained  by  carefully  excising  the  iris 
of  an  albino  rabbit  just  killed,  and  spreading  it  flat  on  the  ob- 
ject glass  in  an  indifferent  liquid.  The  muscular  tissue  of  the 
intestine  can  be  prepared  as  follows:  A  short  portion  of  the 
small  intestine  of  a  rabbit,  or  mature  fetus,  is  filled  with  half 
per  cent,  salt  solution  by  ligaturing  one  of  the  ends,  and  tying 
into  the  other  a  glass  tube  with  a  canulated  extremit}',  through 
which  the  liquid  must  be  injected.  The  gut  having  been  in 
this  way  well  distended,  a  second  ligature  is  placed  between 
it  and  the  canula.  Thin  shreds,  consisting  only  of  the  perito- 
neum and  of  the  longitudinal  muscular  layer,  are  then  stripped 
off  with  the  aid  of  pointed  forceps  from  the  surface  of  the  in- 
testine opposite  to  its  mesenteric  attachment.  These  strips 
are  carefully  spread  out  and  prepared  in  an  indifferent  liquid. 
Of  course  care  must  be  taken  not  to  pierce  the  intestine  with 
the  forceps.  Another  suitable  object  of  study  is  the  abdominal 
extremity  of  the  Fallopian  tube,  which,  in  some  mammalia 
(e.  g.,  in  the  sow),  is  dilated  into  a  large  thin  sac.  It  may  be 
prepared  in  the  same  way  as  the  bladder  of  the  frog.  An  ex- 
cellent method  of  preparing  unstriped  muscle  is  to  immerse  the 
tissue  in  half  per  cent,  solution  of  gold,  for  which  purpose  the 
bladder  of  the  fi*og,  the  mesentery  of  the  newt,  the  iris  of  the 
eyes  of  albino  animals,  or  the  muscular  coat  of  the  intestine 
of  small  mammalia  may  be  used.  The  bladder  of  the  frog  is 
prepared  as  follows  :  A  frog  is  decapitated,  and  the  upper 
two-thirds  of  the  abdominal  cavity  opened.  A  solution  of  chlo- 
ride of  gold  is  injected,  either  by  means  of  a  tube  ten  to  fifteen 
centimetres  in  length,  which  is  drawn  out  at  one  end  so  as  to 
form  a  canula,  and  bent  at  an  obtuse  angle  so  as  to  facilitate 
its  introduction  into  the  bladder,  or,  still  better,  with  the  aid 
of  a  glass  syringe  furnished  with  a  long  beak.  As  soon  as  the 
bladder  is  filled;  a  ligature  is  placed  round  its  neck  and  tight- 
ened round  the  canula,  after  which  the  organ  may  be  excised 
and  placed  in  a  capsule,  containing  a  similar  solution,  for  fif- 
teen minutes.  After  this  time  it  is  cut  into  small  sections, 
which  arc  immersed  in  acidulated  water  and  exposed  to  the 
light.  If  this  method  is  followed,  there  is  no  fear  of  folds  or 
shrinking,  as  the  bladder  is  already  more  or  less  hardened. 
As  soon  as  the  fragments  have  acquired  a  dark  violet  or  dull 


BY    DR.    KLEIN.  67 

red  color,  the  mucous  membrane  is  pencilled  away  and  the  re- 
mainder covered  in  glycerin.  The  mesentery  of  the  newt,  the 
iris,  or  the  muscular  coat  of  the  intestine  of  mammalia  may 
be  prepared  in  the  method  already  explained,  and  then  treated 
in  every  respect  as  just  described.  Chloride  of  palladium, 
which  has  also  been  used  for  the  coloring  of  muscular  fibres, 
has  no  advantage  over  the  gold  salt.  In  sections  of  unstriped 
muscle,  previously  hardened  in  one-eighth  to  one-fourth  per 
cent,  solution  of  chromic  acid,  and  subsequently  colored  in  pic- 
ric acid,  carmine,  aniline,  &c,  the  muscular  bundles  are  dis- 
tinctly seen,  as  well  as  their  relations  to  each  other,  and  to 
the  septa  of  connective  tissue  which  surround  and  separate 
them.1 

In  sections  through  the  hardened  intestine  of  the  frog,  rab- 
bit, or  rat,  the  muscular  cells,  where  they  are  seen  in  longitu- 
dinal section,  appear  to  be  separated  from  each  other,  not  by 
straight  lines,  but  by  marginal  borders,  which  exhibit  fine  trans- 
verse markings,  referable  to  the  existence  of  minute  furrows, 
which  run  in  a  direction  vertical  to  the  axis  of  the  fibre. 

To  isolate  the  individual  muscle-cells  for  the  study  of  their 
form  and  nuclei,  macerating  liquids,  by  which  the  interstitial 
substance  is  disintegrated,  are  employed.  Small  fragments  are 
introduced  into  a  dark  sherry-colored  solution  of  bichromate 
of  potash,  two  or  three  per  cent,  acetic  acid  mixture,  nitx-ic 
acid  diluted  with  four  times  its  volume  of  water,  or  thirty-five 
per  cent,  potash  solution.  The  arrangement  of  the  nerves  of 
unstriped  muscle  will  be  described  in  a  future  chapter. 

Section  II. — Striped  Muscle. 

The  tissue  of  striped  muscles  consists  of  long  cylinders  (mus- 
cular fibres)  which  are  united  by  connective  tissue  into  bundles 
(fasciculi)  of  varying  length.  The  following  parts  have  to  be 
considered  :  The  contents  of  substance  of  the  individual  fibre 
with  its  muscle-corpuscles;  the  sarcolemma  ;  and  the  junction 
of  muscle  with  tendon.  The  mode  of  ending  of  the  nerves  in 
muscle  will  be  described  in  the  next  chapter. 

Proper  Substance  of  Muscular  Fibre. — The  leg  of  a 
water-beetle  (Hydrophilus)  is  torn  out,  and  its  horny  covering 
removed.  A  snip  is  then  taken  from  the  exposed  muscular 
mass,  with  the  aid  of  curved  scissors,  or  a  fine  scalpel,  and  at 
once  covered    without  addition.     If  the   cover-glass  is  then 

1  Fine  sections  of  structures  containing  numerous  unstriped  muscu- 
lar fibres,  which  have  been  hardened  in  chromic  acid,  then  placed  for  a 
few  days  in  diluted  alcohol,  and  finally  stained  in  a  weak  ammoniacal 
solution  of  carmine,  exhibit  a  striking  contrast  between  the  muscular 
fibres  and  the  connective  tissue,  the  former  being  tinged  yellow  by  the 
chromic  acid,  the  latter  red  by  the  carmine. 


68  MUSCULAR    TISSUE. 

slightly  pressed,  so  as  to  flatten  out  the  object,  arhoreseent 
branchings  of  the  tracheae  first  attract  attention.  These  air- 
tubes  consist,  like  the  trachea?  of  mammalia,  of  parallel  rings, 
and  entwine  the  muscular  fibres  with  a  network  of  fine,  dark 
capillaries,  each  of  which  follows  a  winding  or  spiral  course. 
The  muscular  fibres  themselves,  which  either  run  parallel,  or 
cross  each  other  in  various  directions,  are  in  active  movement 
In  some  fibres  this  movement  resembles  that  of  a  wave,  which 
rapidly  progresses  in  the  direction  of  its  length;  in  others, 
when  it  is  slower,  it  has  a  vermicular  character.  On  more 
careful  examination  it  is  seen  that,  during  the  progress  of  the 
wave,  the  muscle  swells,  returning  to  its  original  thickness 
immediately  after.  It  is  further  observed  that  the  dark  paral- 
lel striae  come  nearer  together  during  the  swelling,  and  that 
the  intervals  return  to  their  original  width  after  the  wave  has 
passed.  In  the  contents  of  a  muscular  fibre,  when  in  a  state 
of  rest,  the  following  parts  can  be  distinguished:  (a)  the  dark 
parallel  cross  stripes,  which  as  we  shall  find,  correspond  to 
thin  parallel  disks  of  less  refractive  isotropous  substance 
(called  interstitial  disks) ;  (b)  the  portion  intervening  between 
these.  This,  again,  appears  to  consist  of  two  parts,  viz.,  a 
broader  middle  one  of  dull  gray  appearance,  and  on  either  side 
of  this  a  narrow,  clear  layer.  The  whole  is  made  up  of  highly 
refractive,  anisotropous  contractile  substance,  which  is  to  be 
regarded  as  the  essential  substance  of  the  muscular  fibre.  The 
dark  cross-lines  do  not  seem,  under  high  powers,  homogeneous, 
but  appear  to  consist  of  series  of  contiguous  granules  of  equal 
size.  Many  muscular  fibres  exhibit  no  other  differences;  in 
others,  it  is  possible  to  distinguish  lines  running  longitudinally 
of  greater  or  less  extent,  and  which  are  so  arranged  that  twejr 
come  between  what  appear  to  be  dark  granules  of  the  inter- 
stitial striae.  With  reference  to  these  granules,  it  is  not  to  be 
supposed  that  the}' actually  exist  as  such ;  the  appearance  is 
rather  to  be  regarded  as  expressive  of  the  fact  that  the  dark, 
interstitial  transverse  stripes  are  interrupted  b}r  clear,  longi- 
tudinal lines,  the  interval  between  the  latter  remaining  dark — 
as,  e.g.,  in  a  check  of  which  dark  transverse  lines  are  covered 
by  light  longitudinal  lines.  In  a  fresh  muscular  fibre,  as  seen 
under  the  microscope,  the  transverse  interstitial  disks  are  not 
placed  vertically,  as  we  can  satisfy  ourselves  b}'  using  the  fine 
adjustment,  but  are  set  at  an  oblique  angle  with  the  long  axis 
of  the  muscular  fibre.  In  this  respect  a  muscular  fibre  ma}'  be 
compared  to  a  roll  formed  of  coins  of  different  metals,  so  ar- 
ranged that  the  thin  dark  disks  alternate  with  thicker  light 
ones.  If  such  a  roll  is  laid  on  a  plain  surface,  all  the  coins 
lean  in  one  direction,  and  present  their  edges  to  the  eye,  re- 
garding them  from  above,  just  as  the  disks  in  a  muscular  fibre 
do  under  the  microscope. 


BY    DR.    KLEIN.  69 

We  have  now  to  consider  the  significance  of  the  appearances 
above  described.  The  fact  may  be  stated  in  limine,  that  the 
whole  of  what  intervenes  between  two  interstitial  stripes,  i.  e., 
the  gray  band  and  its  two  bright  borders,  affects  polarized 
light  in  the  same  way — that  consequently  the  view  according 
to  which  only  the  borders  are  doubly  refracting,  is  erroneous. 
If  a  microscope  is  employed,  of  which  the  stage  admits  of  ro- 
tation around  the  vertical  axis  of  the  instrument,  as  in  the 
larger  instruments  of  Hartnack,  and  these  bright  borders 
(which  should  be  distinct  and  regular)  are  observed,  in  a 
muscular  fibre,  under  No.  8  objective,  and  if  the  stage  is  slowly 
rotated,  so  as  to  alter  the  course  of  the  rays  in  relation  to  the 
muscular  fibre  under  observation,  a  remarkable  change  is  seen 
to  take  place  in  these  borders.  As  the  rotation  is  continued 
the  bright  bands  fade,  first  on  one  side  of  the  interstitial  line, 
then  on  the  other,  coming  into  view  again  in  the  same  order; 
the  changes  do  not,  however,  occur  simultaneously  through- 
out the  whole  of  the  muscular  fibre. 

When  fresh  muscular  tissue  is  placed  in  absolute  alcohol, 
and  then  steeped  for  a  few  minutes  in  oil  of  turpentine, 
mounted  in  dammar  varjiish,  and  covered,  only  two  kinds  of 
substance  can  be  distinguished  in  the  fibres,  i.  e.,  dark  inter- 
stitial stripes  and  a  dull  gray  substance  between  them,  without 
a  trace  of  the  clear  borders.  The  longitudinal  section  of  such 
a  muscular  fibre  may  be  represented  diagrammatical^',  as  in 
Fig.  15.  In  the  diagram,  the  slightly  refracting  interstitial 
substance  is  represented  by  a,  the  clear  borders  by  b,  the  dull 
gray  b}r  c.  Let  us  endeavor  to  understand  the  course  of  the 
rays  which  pass  through  b.  Let  $  be  a  ray  which  enters  from 
the  mirror  in  the  direction  a  /3,  and  penetrates  at  o  into  the 
less  refractive  medium  a,  and  passes  through  it  in  the  direc- 
tion o  6 — inasmuch  as  it  deviates  from  the  normal  in  a.  Let 
s'  be  another  ray  which  enters  b  at  the  angle  m',  i.  e.,  a  greater 
angle  than  that  under  which  $  enters.  Aeeordinglj*,  the  de- 
viation it  will  undergo  in  the  medium  a  will  be  greater  than 
the  deviation  undergone  by  $.  And  if  it  be  assumed  that  it 
is  so  great  that  the  sine  of  the  angle  of  deviation^/,  the  angle 
being  a  right  angle,  the  ray  will  pass  out  between  a  and  b.  If 
the  angle  of  incidence  is  greater  than  mf,  the  angle  of  deviation 
is  greater  than  a  right  angle,  so  that  the  ray  does  not  enter  a 
at  all,  but  is  totally  reflected  through  b.  Hence  the  substance 
b  appears  clearer  than  c,  for  more  rays  pass  out  at  b  than  at  c; 
the  excess  consisting  of  those  rays  which,  entering  b  in  a  di- 
rection towards  a,  and  at  a  greater  angle  than  in',  are  totally 
reflected  in  b,  as  above  explained. 

The  bright  borders  of  the  proper  substance  present  the  same 
characters  and  relations  in  the  muscles  of  crabs  after  treat- 
ment with  gold.     Occasionally  they  may  be  also  seen  in  the 


70  MUSCULAR    TISSUE. 

muscles  of  frogs,  and  in  those  of  the  tail  of  the  rabbit,  if  quite 
fresh.  From  these  facts  it  is  evident  that  the  clear  borders 
of  the  proper  substance  need  not  be  regarded  as  actually  ana- 
tomically distinct  from  the  rest,  but  their  presence  can  be  ex- 
plained as  mere  optical  results  of  total  reflection,  i.  e.,  provided 
it  be  admitted  that  the  interstitial  substance  and  the  proper 
substance  refract  light  in  different  degress. 

In  order  to  study  the  longitudinal  stria?  preparations  must 
be  made  in  humor  aqueus  of  the  fresh  muscular  tissue  of 
Hydrophilus,  of  the  sartorius  of  the  frog,  or  of  the  muscles 
of  the  back  of  the  lizard,  care  being  taken  to  separate  the 
muscular  bundles  slightly  from  one  another.  In  such  prepa- 
rations it  is  seen  that  the  substance  which  lies  between  two 
adjoining  transverse  striae  appears  to  be  marked  off  into  a 
number  of  quadrangular  areas  which  correspond  to  the  sides 
of  the  prismatic  "  sarcous  elements." 

A  number  of  such  sarcous  elements,  arranged  in  a  linear 
series  parallel  to  the  axis  of  the  muscle,  and  connected  each 
to  each  by  shorter  disks  of  transparent  intermediary  substance, 
together  constitute  a  so-called  primitive  fibril.  And,  in  ac- 
cordance with  this  definition,  we  can  conceive  each  muscular 
fibre  to  be  formed  of  primitive  fibrils,  along  with  the  interme- 
diary substance  (corresponding  to  the  longitudinal  strife),  by 
which  these  fibrils  are  held  together.  It  is  no  less  possible  to 
conceive  of  the  muscular  fibre  as  consisting  of  disks  (each 
composed  of  a  number  of  laterally  contiguous  sarcous  ele- 
ments, along  with  the  intermediary  substance  by  which  they 
are,  as  just  remarked,  held  together),  separated  each  from 
each  by  thinner  disks  of  intermediary  substance.  The  best 
demonstration  that  the  sarcous  elements  are  the  elements  of 
the  muscular  substance  which  are  arranged  in  disks  trans- 
versely, and  in  fibrils  longitudinally,  is  to  be  obtained  by  the 
method  of  Cohnheim.  A  muscular  fibre  of  a  frog,  Hyrophilus, 
or  cray  fish  is  exposed  in  a  platinum  capsule  to  a  freezing 
mixture,  at  a  temperature  of — G°  C.  to — 8°  C.  After  a  short 
time  the  muscle  acquires  the  consistence  of  wax.  Fine  sec- 
tions are  then  made  with  the  aid  of  a  cooled  razor,  and  are  at 
once  examined  in  a  drop  of  serum  under  a  thin  cover-glass, 
care  being  taken  to  introduce  slips  of  silver  paper  to  avoid 
pressure.  Such  a  preparation,  seen  under  Hartnack's  immer- 
sion objective  No.  10,  exhibits  the  following  facts:  Circular 
or  oval  disks  present  themselves  (cross  sections  of  muscular 
fibres),  the  margins  of  which  are  sharply  defined  and  possess 
a  double  contour  (sarcolemma).  Within  the  sarcolemma  a 
beautiful  mosaic  is  seen,  in  which  the  triangular,  four-sided,  or 
pentagonal  areas  appear  to  consist  of  dull-looking  material, 
separated  by  lines  which  are  brighter,  more  transparent,  and 
refract   light  less  strongly.     These  lines  are,  in  general,  of 


BY    DR.    KLEIN.  71 

extreme  tenuity,  but  certain  spots  are  always  to  be  observed, 
within  which  the  areas  of  dulness  are  further  apart;  in  other 
words,  the  clear  lines  of  demarcation  are  wider.  Wherever 
this  is  the  case  there  exist  sharply  defined  nucleus-like  bodies, 
which,  as  we  shall  find,  are  actually  the  nuclei  of  the  muscle- 
corpuscles.  In  cross  sections  of  muscular  fibres  of  Crustacea, 
insecta,  amphibia,  and  reptilia,  nuclei,  surrounded  by  spots  in 
which  the  clear  lines  are  thicker  than  elsewhere,  are  met  with 
in  all  parts  of  the  fibres  ;  but  in  mammalia  they  occur  only  in 
the  immediate  neighborhood  of  the  sarcolemma.  In  the 
Crustacea  and  in  Hydrophilus,  the  prevalent  form  of  the 
mosaic  is  pentagonal ;  in  the  frog,  four-cornered,  and  usually 
rectangular.  Provided  that  the  preparation  is  protected  from 
pressure  and  evaporation,  it  remains  unaltered  for  several 
days.  If  a  small  quantity  of  water  or  very  dilute  acetic  acid 
is  added  to  the  fresh  preparation,  the  disks  swell  out  in  a 
remarkable  manner;  the  polygonal  areas  become  more  trans- 
parent and  increase  in  size,  while  the  intermediary  substance 
disappears. 

A  fresh  section,  obtained  as  above,  may  be  placed  for  a  few 
minutes  in  diluted  serum  and  then  transferred  for  from  ten  to 
thirty  seconds  to  half  per  cent,  silver  solution  ;  finally,  washed 
in  water  slightly  acidulated  with  acetic  acid,  covered  in  glyce- 
rin, and  exposed  to  light.  A  preparation  is  thus  obtained  in 
which  the  sectional  disks  are  colored  of  various  shades,  from 
clear  yellowish-brown  to  dark-brown.  Clear  white  lines  on  a 
brown  ground  are  seen  with  great  distinctness,  which  corre- 
spond completely  with  the  trellis-work  of  transparent  lines 
seen  in  the  fresh  preparation,  from  which  appearance  we  learn 
that  the  spaces  of  the  mosaic  are  stained  brown  by  silver. 
Oblique  sections,  whether  examined  fresh  or  after  staining 
with  silver,  exhibit  corresponding  appearances.  In  longitudi- 
nal sections,  prepared  according  to  the  same  method,  small 
brown  rectangles,  longer  in  the  direction  of  the  axis  of  the 
muscle  than  in  the  transverse  direction,  which  correspond  to 
the  sarcous  elements,  are  here  and  there  visible.  These 
rectangles  are  separated  from  each  other  by  clear  narrow  lines. 
If  a  very  small  fragment  of  mammalian  or  frog  muscle 
(sartorius  or  mylohyoid  of  the  frog,  or  the  flat  muscle  in  front 
of  the  trachea  of  the  rabbit),  be  steeped  for  fifteen  or  twenty 
minutes  in  chloride  of  gold,  then  exposed  to  light  for  one  or 
two  days  in  slightly  acidulated  water,  and  subsequently 
hardened  in  common  alcohol,  sections  can  be  made  in  planes 
at  right  angles  to  the  axis  of  the  muscle.  These  exhibit 
.-tjtpearances  which  coincide  in  every  respect  with  those  above 
described,  the  only  difference  being  that  the  rectangular  sar- 
cous elements  exhibit  a  clear  red  or  purple  tinge,  while  the 
interstitial  substance  is  dark. 


72  MUSCULAR    TISSUE. 

From  all  those  facts  we  learn  that  the  substance  of  a  mus- 
cular fibre  consists,  in  the  first  place,  of  oblong  prisms,  i.  e., 
sarcous  elements,  with  their  axes  parallel  to  its  axis,  and 
formed  of  a  material  which  refracts  light  strongly,  is  stained 
strongl}-  with  silver,  slightly  with  solution  of  chloride  of  gold, 
and  swells  out  in  the  fresh  state  on  the  addition  of  water  ;  and, 
secondlj',  of  a  less  refractive,  transparent,  interstitial  substance, 
occupying  the  remainder  of  the  space ;  which  is  not  colored  by 
silver,  but  is  intensely  stained  by  chloride  of  gold,  and  dis- 
appears in  dilute  acetic  acid.  This  last  reagent  appears  to 
have  the  faculty  of  dissolving  the  interfibrillar  part  of  the  inter- 
stitial substance,  leaving  the  interstitial  disks  of  the  fibrils 
almost  intact.  Similar  facts  are  observed  in  muscles  which  are 
subjected  to  the  hardening  influence  of  alcohol  or  chromic 
acid.  In  sections  of  muscles  so  prepared,  the  fasciculi  which 
are  cut  transversel}'  are  seen  to  consist  of  disks,  which  are 
either  round  or  flattened  against  each  other,  and  ma}'  be  easily 
stained  in  carmine  or  picric  acid.  In  such  disks  the  double 
contoured  section  of  the  sarcolemma  includes  a  number  of  small 
roundish  corpuscles,  each  of  which,  as  may  be  seen  in  longitu- 
dinal sections,  is  a  fibril  cut  across.  Muscular  fibres,  cut  lon- 
gitudinally, seem  to  consist  mereby  of  fibrils  which  are  divided 
b}T  cross  lines  into  small  long  rods  placed  end  to  end.  In  sec- 
tions of  hardened  tongue  of  the  frog,  it  is  very  easy  to  obtain 
isolated  fibrils  :  the}'  are  also  to  be  seen  in  teased  preparations 
of  other  muscles  hardened  in  alcohol  and  chromic  acid. 

The  Sarcolemma. — Each  muscular  fibre  is  invested  in  a 
structureless  hyaline  membrane.  To  demonstrate  it,  the  readiest 
method  is  to  add  water  to  a  fresh  preparation  of  Hydrophilus, 
or,  better,  frog  muscle.  After  a  short  time  the  sarcolemma 
separates  in  transparent  bulgings  with  double  contours. 
Greater  lengths  of  sarcolemma  can  be  shown,  by  carefully 
teasing  fresh  frog-muscle  in  salt  solution.  In  such  a  prepara- 
tion, fibres  are  always  to  be  found,  which,  over  a  greater  or 
less  extent,  are  no  longer  striated,  but  consist  of  a  finely 
granular  mass.  Continuing  the  observation,  it  is  seen  that  the 
parts  of  the  fibre  on  either  side  of  such  a  spot  become  con- 
tracted, as  indicated  by  the  approximation  of  the  transverse 
striae,  and  by  the  widening  of  the  fibre.  By  virtue  of  this  con- 
traction, the  granular  muscular  substance  is  torn  asunder,  the 
sarcolemma  being  brought  into  view  as  a  transparent  tube. 
Within  this  tube  a  greater  or  less  number  of  granules  are  ob- 
served in  active  molecular  movement.  As  the  disintegration 
of  the  muscular  substance  progresses,  an  increasing  quantity 
of  sarcolemma  is  brought  into  view.  The  broken  up  ends  (if 
muscular  substance  are  always  irregular  in  form,  presenting 
numerous  projections,  none  of  which  exhibit  striation.  By  and 
by  fresh  spots  become  the  seat  of  the  same  change,  so  that  the 


BY    DR.    KLEIN.  73 

disintegrated  parts  are  separated  from  each  other  only  by 
short  intervals  of  normal  muscle.  By  drawing  asunder  a  small 
number  of  muscular  bundles,  their  opposite  ends  being  seized 
with  fine  forceps,  a  preparation  may  be  obtained  which  shows 
similar  appearances  in  a  larger  proportion  of  fibres. 

The  extraordinary  power  of  resistance  of  the  sarcolemma 
may  be  shown  as  follows  :  One  of  the  hind  legs  of  a  tadpole  is 
amputated  at  the  thigh.  The  animal  is  then  replaced  in  water. 
After  fort3'-eight  hours,  the  loosened  muscular  fibres  hang  from 
the  stump  in  long  pencils.  If  these  are  cut  off"  close  to  the  sur- 
face of  the  stump  with  sharp  scissors,  and  covered  in  water, 
the}'  are  found  to  consist  of  a  number  of  hyaline  tubes,  which, 
when  seen  in  profile,  present  doubfy  contoured  edges.  Next 
the  cut  edge  some  of  them  contain  a  plug  of  striped  muscular 
substance,  or  of  coarsely  granular  material,  which  is  divided 
into  a  number  of  closely  packed  polyhedral  cells.  In  the  rest 
of  the  tubes,  coarsely  granular  young  cells  are  seen  sprouting 
from  the  internal  surface. 

Muscle-Corpuscles. — In  preparations  of  fresh  muscle 
(newt,  frog,  or  Hydrophilus)  numerous  nuclei  occur,  which  in 
the  Hydrophilus  are  roundish,  in  the  frog  oblong  or  staff- 
shaped.  If  dilute  acetic  acid  be  added,  the  muscular  substance 
becomes  swollen  and  transparent,  and  the  nuclei  are  seen  very 
distinctly,  each  embedded  in  granular  protoplasm,  which  has 
the  form  of  a  spindle-shaped  cell,  the  long  axis  of  which  is 
parallel  to  that  of  the  fibre.  If,  on  the  other  hand,  we  examine 
an  oblique  or  cross  section  of  frozen  muscle,  covered  in  dilute 
acetic  acid,  it  is  easy  to  satisfy  one's  self  that  the  nuclei  in 
question  are  not  embedded  in  fusiform  protoplasmic  masses, 
but  in  finely  granular  lamella?,  which  are  seen  to  be  dotted 
about  the  whole  thickness  of  the  fibre,  and  may  be  either  di- 
vided or  simple.  The  distribution  of  these  lamellae  in  the 
muscular  fibre  differs  in  different  animals.  In  mammalia,  they 
are  confined  to  the  immediate  neighborhood  of  the  surface;  in 
the  Hijdrophilus,  crab,  newt,  and  frog,  they  constitute  a  net- 
work within  the  muscular  fibre,  exhibiting  marked  differences 
in  thickness,  not  only  between  different  lamella?,  but  between  dif- 
ferent parts  of  the  same  lamella.  In  fresh  muscle  of  Dytiscus 
marginalia,  the  arrangement  of  these  protoplasmic  masses  is  as 
follows:  In  some  muscular  fibres,  the  granular  protoplasm  has, 
throughout  the  fibre,  the  form,  more  or  less,  of  cylindrical  bands, 
in  which  roundish  nuclei  are  arranged  close  together  in  linear 
scries.  Here  and  there,  these  nuclei  are  separated  by  distinct 
marks,  so  that  the  whole  cylinder  seems  as  if  divided  into  por- 
tions, each  corresponding  to  a  nucleus.  In  other  fibres,  there 
are.  in  place  of  an  axial  cylinder  of  protoplasm,  two  or  three 
lamella:  which  are  continuous  with  each  other  by  subordinate 
lamella?  of  various  extent.     In  these,  roundish  nuclei  arc  em- 


74  MUSCULAR    TISSUE. 

bedded  at  various  distances,  and  in  cross  sections  they  appear 
thicker  at  the  level  of  the  nuclei.  In  an  optical  longitudinal 
section,  in  which  a  lamina  is  seen  in  its  whole  length,  it  is  ob- 
served to  be  usually  curved.  In  a  transverse  section  it  is  also 
often  curved.  We  therefore  conclude  that  these  lamellae  are 
composed  of  placoid  cells,  each  of  which  corresponds  to  a  nu- 
cleus, and  constitutes  a  muscle-corpuscle,  the  limits  of  which 
are  indicated  by  the  markings  often  seen  between  neighboring 
nuclei.  In  Hydrophilus,  muscular  fibres  are  also  met  with,  in 
which  the  lamellae  are  replaced  by  cylinders. 

In  the  individual  muscular  fibres  of  the  tongue  of  the  frog, 
obtained  by  taking  a  snip  from  that  organ  near  the  surface, 
and  covering  it  at  once  with  serum,  chains  of  oblong  nuclei,  or 
large  groups  of  nuclei  without  definite  arrangement,  are  to  be 
found  here  and  there.  In  the  latter  case,  the  nuclei  are  not  all 
oblong;  some  of  them  are  constricted  and  possess  knobs.  In 
sections  of  tongue  stained  in  gold,  it  is  seen  that  these  chains 
and  groups  of  nuclei  are  embedded  in  granular  protoplasm, 
which  is  continuous  with  the  granular  lamellae  above  described. 
These  bodies  are  therefore  to  be  regarded  as  enlarged,  many- 
nucleated  muscle-corpuscles. 

Tendinous  Insertions. — The  transition  from  muscle  to 
tendon  takes  place  in  two  ways:  In  one  the  transverse  striae 
cease,  the  whole  muscular  fibre  passing  into  a  tendinous  bundle 
of  the  same  size,  consisting  of  parallel  wavy  fibres.  In  the 
other,  the  muscular  fibre  tapers  to  a  blunt  point,  the  sarco- 
lemma  extending  beyond  it  as  a  thread-like  structure  of  vary- 
ing thickness,  resembling,  and  becoming  continuous  with,  a 
slender  bundle  of  connective  tissue.  Oblong  cellular  structures 
may  be  seen  in  this  fibre.  The  first  form  may  be  very  easily 
and  complete!}'  demonstrated  in  a  teased  preparation  in  serum 
or  saline  solution,  in  the  muscular  layer  which  extends,  in 
Hijdrophilus,  from  the  trunk  to  the  first  joint  of  the  extremi- 
ties, or  in  a  similar  preparation  of  the  thoracic  cutaneous 
muscle  of  the  frog.  In  the  latter  case,  care  will  be  necessary 
to  remove  the  tendinous  insertions  along  with  the  muscle,  and 
to  spread  out  the  whole  in  serum  or  saline  solution  before 
covering  it.  The  second  form  can  be  studied  in  fresh  teased 
preparations  of  the  muscles  of  the  limbs  of  small  mammalia, 
or  of  the  muscles  of  the  larynx;  but  more  easily  in  very  thin 
sections  of  the  tongue  of  man  or  of  mammalia,  especially  in 
those  fibres  which  radiate  upwards  towards  the  dorsal  mucous 
membrane.  In  sections  of  tongue  hardened  in  chromic  acid, 
which  are  made  across  the  long  axis  of  the  organ,  bundles  of 
fibres  are  seen  to  pass  upwards  between  the  transversely  cut 
bundles  of  the  longitudinalis  linguae.  Of  these  bundles  it  is 
seen  that  certain  of  the  muscular  fibres  stop  short,  the  sarco- 
lemma  being  prolonged  into  a  thread,  as  above  described.    The 


BY    DR.    KLEIN.  75 

rest  of  the  muscular  fibres  enter  the  mucosa,  and  end  in  ten- 
dinous bundles  of  equal  diameter,  which  again  unite  with  the 
mesh  work  of  the  mucosa. 

Arrangement  and  Division  of  Muscular  Fibres. — 
They  are  grouped  into  bundles  by  septa  of  connective  tissue, 
which  in  general  contain  numerous  amoeboid  cells,  and  a  net- 
work of  ordinary  branched  cells.  From  these  septa  thinner 
lamellae  spring,  which  are  interposed  between  the  individual 
bundles.  In  a  mature  foetus  a  cross  section  of  muscular  bun- 
dles, e.g.,  of  the  tongue,  palate,  or  eyelids,  shows  that  they  are 
intersected  by  a  beautiful  network  of  nucleated  branched  cells, 
in  such  a  way  that  each  mesh  is  occupied  by  a  single  fibre.  In 
general,  striated  muscles  do  not  divide:  there  are,  however, 
situations  in  which  muscular  fibres  are  seen  to  divide  dicho- 
tomously  or  dendritically.  The  best  example  is  to  be  found  in 
the  cardiac  muscular  fibres,  of  which  a  repeated  dichotomous 
division  is  characteristic,  as  also  their  union  with  one  another 
so  as  to  form  a  network.  In  the  tongue  of  mammalia,  the 
muscular  fibres  often  divide  before  ending  in  tendons;  but  in 
that  of  the  frog  the  divisions  occur  much  more  frequently. 
Both  in  recent  preparations,  and  in  sections  made  after  hard- 
ening, muscular  fibres  are  seen  which  branch  dendritically,  as 
they  ascend  towards  the  dorsal  mucous  membrane,  the  ulti- 
mate branches  being  so  small  that  they  contain  only  a  few 
fibrils,  which  finally  end  in  connective  tissue  fibres. 

Examination  of  Muscular  Fibre  in  Polarized  Light. 
— We  assume  the  reader  to  be  acquainted  with  the  action  of  a 
Nicol's  prism,  contenting  ourselves  with  stating  that  the  polari- 
zation microscope  is  an  ordinary  microscope,  in  which  one 
Nicol  is  placed  above  the  eye-piece  or  ocular  (i.e.  between  the 
eye-glass  and  the  observer's  eye),  and  a  second  between  the 
object  and  mirror.  The  upper  Nicol  is  usually  of  one  piece 
with  the  ocular.  The  prism  is  so  fixed  that  it  can  be  rotated, 
and  that  the  axis  of  rotation  is  contained  in  its  principal  plane. 
The  degree  of  rotation  is  measured  by  a  graduated  circle. 
The  lower  Nicol  is  surrounded  by  a  condensing  lens,  and  can 
(in  Ilartnack's  microscope)  be  fitted  into  the  tube  which 
ordinarily  contains  the  diaphragm  or  condensor.  In  looking 
through  such  a  microscope,  it  is  seen  that  the  illumination  of 
the  field  varies  according  to  the  relative  position  of  the  two 
prisms;  so  that,  in  rotating  the  upper  one  (which  is  called  the 
analyzer),  it  is  darkened  and  lightened  twice  in  each  complete 
rotation.  The  positions  of  greatest  obscurity  are  those  in 
which  the  principal  planes  of  the  two  Nicols  are  at  right  angles 
to  each  other — of  greatest  luminousness,  those  in  which  these 
planes  are  coincident.  When  the  microscope  is  used 'with  the 
Nicol  in  the  first-mentioned  position,  the  object  is  said  to  be 
observed  between  crossed  Nicols. 


76  MUSCULAR   TISSUE. 

Before  proceeding  to  describe  what  is  seen  in  muscle  when 
examined  between  crossed  Nicols,  the  facts  observed  when 
crystals  which  possess  similar  optical  properties  arc  looked  at 
in  the  polarizing  microscope,  should  be  first  carefully  studied. 
Muscular  fibres  can  be  shown  to  possess  optical  properties  which 
resemble  those  of  doubly  refractive,  positive,  uniaxial  crystals, 
such,  e.  jy.,  as  those  of  rock  crystal  or  quartz,  etc.  The  meaning 
of  these  expressions  must  be  illustrated.  If  a  number  of  doubly 
refracting  microscopical  crystals  of  any  kind  are  placed  under 
the  polarizing  microscope,  it  is  seen  that  when  the  upper  Xicol 
(or  analyzer)  is  rotated  so  as  to  make  the  field  dark,  the  crys- 
tals appear  (according  to  their  position)  more  or  less  illumin- 
ated ;  whereas  this  is  not  the  case  if  the  crystals  are  isotropous, 
i.  e.,  belong  to  the  "  regular"  system  of  crystallization. 

The  degree  of  illumination  of  each  crystal  varies  according 
to  its  position.  This  may  be  readily  shown  by  rotating  the 
object-glass,  or  stage  on  which  it  lies,  without  moving  either 
prism  :  it  is  then  seen,  as  regards  each  crystal  (supposing  the 
Nicols  to  be  crossed),  that  four  times  in  each  complete  rotation 
it  loses  its  luminousness  altogether.  These  two  positions  are 
called  the  inactive  azimuths,  because  the  body  looks  in  these 
positions  as  if  it  were  isotropous — dark  on  the  dark  field. 
This  happens  whenever  the  principal  plane  of  the  crystal  lies 
in  the  principal  plane  of  either  Nicol,  and  is  consequently  at 
right  angles  to  that  of  the  other.  In  all  other  positions  it  looks 
more  or  less  illuminated,  the  degree  of  brightness  increasing 
and  diminishing  as  the  azimuth  in  which  it  is  placed  declines  or 
approaches;  consequently,  the  crystal  appears  brightest  when 
its  principal  plane  is  inclined  at  an  angle  of  45°  to  the  plane  of 
polarization.  When  the  crystalline  body  is  of  a  certain  thick- 
ness, the  appearances  are  somewhat  different.  Thus,  if  a  plate 
of  mica  from  one  to  two  millimetres  thick  is  placed  on  the  ob- 
ject-glass with  the  Nicols  crossed,  it  is  seen  that  the  field  is  not 
only  luminous  but  colored,  the  color  varying  according  to  the 
thickness  of  the  plate — its  intensity  varying  according  to  the 
inclination  of  the  principal  plane  of  the  mica  to  that  of  the 
prisms,  being  brighest  when  that  inclination  is  45°.  If  now  the 
plate  of  mice  is  rotated,  it  is  seen  that  in  each  rotation,  as  be- 
fore, there  are  four  azimuths  of  greatest  brightness,  and  four 
intervening  ones  of  greatest  obscurit}'.  But,  in  addition  to 
this,  it  is  observed  that,  in  the  bright  azimuths,  the  colors  dis- 
played differ — the  color  of  the  field  in  any  given  position  of  the 
plate  being  complementary  to  that  seen  when  it  is  rotated  90°. 
These  facts  are  of  great  practical  importance  in  all  eases  in 
which  it  is  desired  to  observe  the  doubly  refractive  parts  of 
transparent  objects  between  crossed  Nicols,  without  losing 
sight  of  those  parts  which  are  isotropous.  If  such  objects  are 
examined  in  the  ordinary  way  in  the  dark  field,  it  is  obvious 


BY    DR.    KLEIN.  77 

that  all  those  parts  which  are  isotropous  are  invisible.  If, 
however,  the  field  is  colored,  by  placing  a  plate  of  mica  or 
selenite  underneath  the  object,  everything  is  seen  as  distinctly 
as  if  the  light  were  not  polarized,  with  the  difference  that  the 
doubly  refractive  bodies  are  distinguished  from  others  by  their 
color — the  latter  being  of  the  color  of  the  field,  the  former  of  a 
color  differing  from  it  variously,  according  to  their  thickness, 
their  position,  and  their  optical  properties.  In  all  doubby  re- 
fracting ciystals,  there  is  at  least  one  direction  in  which  light 
ma}r  be  transmitted  without  suffering  double  refraction — i.  e., 
bifurcation.  Those  crystals  in  which  there  is  only  one  such 
direction  are  called  uniaxial,  e.  g.,  Iceland  spar,  qtiartz,  and 
tourmaline.  When  such  crystals  are  examined  between  crossed 
Nicols,  in  such  a  position  that  the  light  is  transmitted  through 
them  in  the  direction  above  referred  to  (which  is  always  that 
of  the  axis  of  ciystallization),  they  are  not  seen.  We  shall  find 
that  the  same  holds  good  as  regards  the  anisotropous  parts 
of  muscular  fibre. 

In  a  fresh  muscular  fibre  seen  between  crossed  Nicols,  the 
first  fact  that  strikes  one  is  that  the  appearances  correspond 
with  those  observed  in  doubly  refracting  bodies.  Next  it  is 
seen  that  all  the  muscular  fibres  under  observation  are  not 
equally  illuminated.  Those  are  brighest  which  are  so  placed 
that  the  long  axis  forms  an  angle  of  45°,  the  illumination  di- 
minishing as  the  angle  diminishes,  until  it  disappears  at  the 
moment  that  the  fibre  axis  lies  in  the  plane  of  polarization  of 
either  Nicol.  It  is  further  seen  that  all  parts  of  the  muscular 
fibre  are  not  doubly  refracting,  but  only  those  parts  which 
were  before  described  as  sarcous  elements.  The  interstitial 
substance  looks  dark  whatever  be  the  position  of  the  fibre,  so 
that  between  crossed  Nicols  it  is  invisible. 

The  method  to  be  adopted  for  demonstrating  these  facts  is 
as  follows  : — 

Method. — From  a  number  of  plates  of  selenite  or  mica,  one 
is  selected  which,  when  placed  in  the  proper  azimuth,  gives  be- 
tween crossed  Nicols  a  field  of  the  tint  which  is  known  as 
teinte  de  passage.1  Such  a  plate  having  been  found,  it  is  fixed 
to  the  object-glass  with  a  drop  of  dammar.  Fresh  muscular 
fibres  of  the  extremities  of  the  crab,  frog,  or  hydrophilus,  are 
placed  in  absolute  alcohol  for  half  an  hour,  or  in  ordinary  al- 
cohol for  several  days.  As  soon  as  the  muscular  tissues  are 
deprived  of  water,  they  are  soaked  in  oil  of  turpentine.     Of  the 

1  The  teinte  de  passaged  a  peculiar  purple  violet,  and  lies  between 
red  and  blue  in  this  sense,  that  if  the  plate  possess  a  thickness  a  shade 
greater  than  that  which  produces  the  tint  required,  the  color  is  blue  ;  if 
a  shade  less,  red.  These  facts  are  of  importance  as  aids  in  selecting 
a  plate. 


70  MUSCULAR    TISSUE. 

muscle  so  treated,  a  preparation  is  made  on  the  plate  of  mica 
above  mentioned,  the  muscular  fibres  being  teased  in  such  a 
way  that  they  lie  in  various  directions.  If  the  preparation  is 
now  examined  in  the  purple  fU'ld  (obtained  as  above  described), 
the  different  colors  of  the  individual  muscular  fibres  arc  brought 
out  with  the  greatest  distinctness.  On  rotation  of  the  upper 
Nicol  they  undergo  changes:  if  the  rotation  extends  to  'J0C, 
each  color  is  replaced  by  its  complementary.  In  a  cross  section 
of  a  muscle  (of  any  animal)  hardened  in  alcohol,  and  prepared 
in  dammar  varnish  after  steeping  in  turpentine,  the  individual 
fibres  show  various  degrees  of  illumination.  All  transitions 
present  themselves  between  those  which  are  bright  between 
crossed  Nicols,  and  those  which  are  completely  invisible;  and 
it  is  found  that  the  latter  are  those  which  are  cut  in  planes  at 
right  angles  to  their  axis — the  former,  those  cut  at  an  angle  of 
45°  to  their  axis.  It  is  thus  seen  that  the  long  axis  of  a  mus- 
cular fibre  corresponds,  in  relation  to  its  properties  of  double 
refraction,  to  the  axis  of  crystallization  of  a  uniaxial  crystal — 
in  short,  that  a  muscular  fibre  is  optically  comparable  to  such 
a  crystal.  Briicke  has  further  demonstrated,  not  only  that  the 
muscular  fibres  are  uniaxial,  but  also  that  they  are  positive, 
i.  e.,  that  they  resemble  those  uniaxial  crystalline  bodies  in 
which  the  extraordinary  index  of  refraction  exceeds  the  ordi- 
nary index.  Inasmuch  as  the  apparatus  necessary  for  demon- 
strating this  is  not  to  be  found  in  most  laboratories,  and  an 
explanation  of  the  mode  in  which  it  is  accomplished  would  in- 
volve a  more  general  discussion  of  the  subject  of  polarization 
than  our  space  allows,  it  has  been  omitted.  The  reader  is  re- 
ferred to  Briicke's  article  in  Strieker's  Histology  for  further 
information. 

If  a  teased  preparation  of  the  fresh  muscle  of  a  frog  is 
treated  with  water  and  covered,  the  ends  of  the  muscles  swell, 
and  the  contents  project  as  a  transparent  granular  mass,  in 
which  the  strire  are  no  longer  visible.  Between  crossed  Nicols 
these  parts  are  found  to  be  doubly  refractive,  and  look  like  a 
silver-gray  cloud  of  dust  on  the  dark  ground.  The  particles 
of  which  the  cloud  consists  are  regarded  by  Briicke  as  the 
real  elements  of  the  doubly  refracting  substance.  They  are 
the  constituents  of  the  sarcous  elements,  and  are  called  Dis- 
diaklasts.  The  disaggregation  of  the  sarcous  elements  is  de- 
termined by  the  water. 


BY    DR.    KLEIN.  79 


CHAPTER  V. 

TISSUES  OF  THE  NERVOUS  SYSTEM. 
Section  I. — Nerve  Fibres. 

According  to  the  presence  or  absence  of  the  medulla  which 
surrounds  their  central  and  essential  part,  viz.,  the  axis- 
cylinder,  nerve  fibres  are  distinguished  as  medullated  and 
non-racdullated.  The  presence  or  absence  of  the  so-called 
Schwann's  sheath  affords  an  additional  and  subordinate  dis- 
tinction. This  sheath  is  a  resistant,  elastic,  sometimes  fibril- 
lated,  but  more  commonly  homogeneous,  membrane,  contain- 
ing a  variable  number  of  oval  nuclei. 

Axis-Cylinder. — All  nerve  fibres  contain  an  axis-cylinder ; 
it  is  a  solid  cylindrical  structure,  which,  under  the  highest 
powers,  is  seen  to  be  made  up  of  the  most  delicate  fibrils 
(primitive  fibrils).  It  varies  in  size,  in  accordance  with  the 
thickness  of  the  nerve  fibre.  As  it  approaches  the  periphery, 
it  splits  into  its  constituent  fibrils  by  repeated  division,  or  by 
giving  off  smaller  lateral  branchlets.  To  demonstrate  the 
fibrillated  structure  of  the  axis-cylinder,  a  fresh  nervous 
bundle  may  be  prepared  from  the  lateral  columns  of  the  spinal 
cord  of  a  small  mammal,  from  the  optic  nerve,  the  olfactory 
nerve,  or  from  some  nerve  belonging  to  the  sympathetic  sys- 
tem. The  preparation  must  be  macerated  for  twenty-four 
hours  in  iodized  serum,  and  then  further  prepared  by  teasing 
with  needles.  In  the  nerve  fibres  of  the  lateral  columns  of  the 
spinal  cord,  the  structure  of  the  axis-cylinder  may  also  be 
shown  in  preparations  which  have  been  steeped  for  several 
days  in  diluted  solution  of  bichromate  of  potash.  In  prepa- 
rations thus  obtained,  many  of  the  fibres  are  seen  to  exhibit 
points  at  which  the  medullary  sheath  is  broken,  in  conse- 
quence of  which  the  pale,  finely  striated  axis-cylinder  becomes 
visible.  Fibrillar  structure  may  also  be  readily  demonstrated 
in  the  processes  of  the  ganglion  cells,  and  in  the  pale  naked 
axis  cylinders  of  various  thicknesses  of  the  nervous  centres. 
Again,  in  the  fresh  tadpole's  tail,  as  prepared  in  serum  or  in 
half  per  cent,  salt  solution,  fibrillar  structures  can  be  seen 
with  great  distinctness  in  the  peripheral  branching  axis-cylin- 
der. This  structure  is  not,  however,  peculiar  to  the  peripheral 
or  central  portions  of  the  course  of  a  nerve,  but  exists  in  other 
parts.     To  show  this,  the  best  way  is  to  place  the  fresh  nerve 


80  TISSUES    OF    THE   NERVOUS    SYSTEM. 

in  common  alcohol  for  a  few  minutes,  and  to  stain  the  prepa- 
ration with  carmine.  It  must  then  be  put  in  absolute  alcohol 
for  twenty  to  thirty  minutes,  after  previously  teasing  it  out 
somewhat.  If  it  is  allowed  to  remain  twelve  hours  or  more  in 
oil  of  turpentine,  and  then  covered  in  dammar  varnish,  it  will 
be  found  that  all  the  nerve  fibres  are  more  or  less  completely 
deprived  of  their  medullary  sheaths.  The  axis-cylinder  ap- 
pears in  general  to  consist  of  granulous  substance,  but  here 
and  there  distinct  longitudinal  streaking  can  be  recognized. 
The  axis-cylinder  can  also  be  freed  of  its  medullary  sheath  if 
chloroform  or  collodion  be  added  to  a  teased  preparation  of 
fresh  nerve,  which  is  as  nearly  dry  as  possible  without  being 
thoroughly  desiccated.  Occasionally  the  primitive  fibrils  of 
the  non-medullated  nerve  fibres  are  beset  with  small  varicosi- 
ties at  nearly  regular  intervals,  which,  when  treated  with  cer- 
tain reagents  (perosmic  acid,  chloride  of  gold),  become  very 
distinct. 

Medullary  Sheath. — In  a  teased  preparation  of  a  fresh 
sciatic  nerve  of  the  frog,  in  half  per  cent,  salt  solution,  the 
individual  nerve  fibres  are  seen  to  be  invested  by  a  sheath  of 
transparent,  highly  refractive  material,  which,  when  it  presents 
its  surface,  appears  hyaline,  but,  as  seen  at  the  edge  of  the 
nerve,  exhibits  a  double  outline.  Thus  the  medullary  sheath 
confers  on  the  nerve  fibre  a  dark  edge  or  double  contour;  so 
that  these  appearances  in  a  nerve  are  characteristic  of  its 
presence.  Soon  after  the  preparation  has  been  made,  it  is  ob- 
served that  the  sheaths  of  many  fibres  become  beset  with  drop- 
like bodies  of  irregular  form,  which  are  either  bright  and 
shining,  or  granulous  and  turbid.  The}r  are  produced  by  a 
coagulation  of  the  medulla.  In  preparations  made  in  iodized 
serum,  the  fibres  remain,  however,  for  several  hours  quite 
smooth,  without  undergoing  this  change.  In  the  nervous 
centres,  the  medullated  fibres  which  possess  no  Schwann's 
sheath  often  present  a  necklace-like  appearance,  due  to  this 
coagulation  of  the  medullary  sheath  (the  so-called  varicose 
fibres).  The  medullary  sheath  exhibits  a  remarkable  arrange- 
ment at  those  points  of  the  course  of  the  nerve  at  which  it 
divides  into  two  or  more  branches.  At  such  points  the  sheath 
becomes  considerably  attenuated,  as  well  as  contracted.  To 
show  this,  the  membrana  nictitans  of  a  frog  is  carefully  ex- 
cised, spread  out  in  a  drop  of  humor  aqueus,  and  covered — 
care  being  taken  to  introduce  strips  of  paper  under  the  cover- 
glass  so  as  to  prevent  pressure.  The  thoracic  cutaneous 
muscle  of  the  frog  may  be  prepared  in  the  same  way.  Where 
a  medullated  nerve  fibre  passes  into  a  non-medullated,  as  in 
the  objects  above  mentioned,  the  sheath  is  usuall}'  thinned  out 
towards  the  point  where  it  is  about  to  cease,  in  which  case 
the  thin  portion  ma}7  either  extend  up  to  the  line  at  which  it 


BY    DR.    KLEIN.  81 

abruptly  terminates,  or  may  end  in  a  terminal  thickened  bor- 
der. In  other  instances,  more  particularly  in  the  striated 
muscles,  the  sheath  very  often  stops  suddenly  without  any 
previous  attenuation. 

Neurilemma. — In  order  to  make  out  satisfactorily  the 
relation  of  the  nerve  fibres  in  a  nerve  trunk,  sections  must  be 
prepared,  either  of  nerves  hardened  in  alcohol,  or  in  diluted 
chromic  acid,  and  must  then  be  stained  with  carmine  ;  or  tis- 
sues known  to  be  richly  supplied  with  nerves  must  be  em- 
ployed, c-g-i  tongue,  oesophagus,  trachea,  urinary  bladder,  etc. 
In  cross  sections  of  nerves,  the  nerve  fibres  are  seen  to  be  in- 
closed in  a  well-defined  connective-tissue  sheath  (neurilemma), 
of  thickness  more  or  less  proportional  to  that  of  the  nerve 
itself.  Between  the  fibres  of  the  neurilemma,  cellular  struc- 
tures are  met  with.  In  many  nerve  trunks,  septa  stretch  in- 
wards from  the  sheath,  by  which  the  nerve  fibres  are  divided 
into  a  greater  or  less  number  of  bundles.  In  such  preparations 
the  cross  sections  of  each  nerve  fibre  exhibit  an  external  ring 
with  double  contour — the  cut  edge  of  the  medullary  sheath — 
inclosing  a  body  of  circular  outline  which  does  not  fill  up  the 
whole  of  the  space,  and  is  readily  stained  by  carmine.  In  a 
longitudinal  section  of  a  nerve  we  observe,  within  the  connec- 
tive-tissue sheath,  the  double  contoured  fibres,  running  parallel 
with  each  other,  but  following  a  more  or  less  wavy  course,  and 
showing  the  nuclei  of  their  Schwann's  sheaths.  In  newly-born 
children  the  number  of  nuclei  is  much  greater  than  in  adults. 
The  spinal  nerves,  which  in  the  frog  find  their  way  to  the  skin 
from  the  spinal  cord  through  the  dorsal  lymph  sac,  possess  an 
extraordinarily  thick  neurilemma ;  this  is  covered  by  a  layer 
of  endothelium,  which  can  be  demonstrated  by  staining  with 
nitrate  of  silver.  In  the  neurilemma  of  many  microscopical 
nerves,  fine  capillary  vessels  can  often  be  made  out.  For  the 
tracing  out  of  medullated  fibres,  the  use  of  osmic  acid  is  of 
great  value;  for  the  medullary  sheath  is,  in  consequence  of 
the  fatty  matter  it  contains,  stained  dark  by  this  reagent. 

Schwann's  Sheath. — With  the  exception  of  the  optic 
and  auditory  nerves,  the  fibres  of  all  peripheral  nerves  possess 
a  Schwann's  sheath.  The  nuclei  which  the  sheath  contains 
are  seen,  when  examined  in  the  fresh  state  in  indifferent  fluids, 
to  be  pale,  and  more  or  less  distinctly  granular.  When  acted 
on  l»y  acids  or  hardening  reagents,  they  shrink.  In  freshly 
prepared  teased  preparations  (e.g.,  of  the  sciatic  nerve  of  the 
frog),  the  Schwann's  sheath  of  the  wide  medullated  fibres  can 
be  recognized  with  great  difficulty.  In  general,  only  the 
nuclei  can  be  made  out.  The  sheath  itself  can  be  more  easily 
seen  in  the  narrow  non-medullated  fibres.  In  the  nerves  of 
Lbe  tail  of  the  tadpole,  and  of  the  membrana  nictitans  of  the 
frog,  in  those  of  the  mesentery  of  the  frog  and  of  mammalia 
6 


82  TISSUES    OF   THE   NERVOUS   SYSTEM. 

"whether  in  the  fresh  state  or  treated  with  gold,  in  the  cornea 
of  t he  frog  or  of  mammalia  treated  with  gold,  in  sections  of 
the  epiglottis  or  of  the  mucous  membrane  of  the  mouth  made 
after  treating  the  tissue  with  gold — the  Schwann's  sheath  can 
be  often  recognized  as  a  more  or  less  distinctly  streaked  mem- 
brane. It  generally  ceases  where  the  non-medullated  fibres 
split  into  their  constituent  fibrils. 

Non-medullated  Fibres. — Various  methods  must  be 
used  for  the  demonstration  of  the  non-medullated  fibres,  for 
the  same  method  does  not  answer  equally  well  in  all  cases. 
Among  these,  chloride  of  gold  has,  unquestionabl}',  the  first 
place.  In  very  many  instances  it  affords  the  only  means  we 
have  of  following  these  fibres  to  their  finest  ramifications,  e.g., 
in  the  skin,  mucosa,  cornea,  and  striped  muscular  tissue,  etc. 
Osmic  acid  is  also  very  useful.  The  silver  method,  or  treat- 
ment with  certain  acetic  acid  mixtures,  is  occasionally  em- 
ployed. In  membranes  which  are  prepared  in  the  fresh  state 
in  an  indifferent  liquid,  individual  non-medullated  nerve  fibres 
can  be  seen,  but  their  finer  ramifications  cannot  be  traced,  even 
in  the  most  transparent,  without  the  aid  of  the  reagents  above 
mentioned. 

Section  II. — Nekve  Cells. 

Nerve  Cells,  i.e.,  ganglion  cells,  may  be  investigated  (a) 
in  the  ganglia  which  are  attached  to  the  spinal  and  certain 
cerebral  nerves  ;  (b)  in  the  gray  substance  of  the  brain  and 
spinal  cord ;  (c)  in  ganglia  belonging  to  the  sympathetic 
system. 

(a)  Ganglia  of  the  Cranial  and  Spinal  Nerves. — As 
may  be  seen  in  sections  of  these  ganglia  (hardened  in  chromic 
acid  or  Midler's  fluid),  each  of  them  is  inclosed  in  a  capsule. 
This  capsule  varies  in  thickness  in  different  ganglia,  and  is 
continuous  with  the  neurilemma  of  the  nerves  which  enter  and 
leave  the  ganglion.  It  consists  of  fibrillated  connective  tissue, 
in  which  the  cellular  elements  proper  to  that  tissue  ma}'  be 
distinguished.  From  it  septa  of  connective  tissue  stretch  in- 
wards, and  unite  by  anastomosis  so  as  to  form  a  meshwork. 
This  meshwork  serves  to  support  the  rich  vascular  system  with 
which  the  ganglion  is  provided.  Its  meshes  arc  occupied  by 
the  nerve  fibres  and  b}r  ganglion  cells.  These  last  consist  of  a 
substance  partly  granulous,  partly  fibrillated,  in  which  a 
vesiculated,  spheroidal,  sometimes  oblong,  nucleus  is  em- 
bedded, which  itself  incloses  a  shining  nucleolus,  the  position 
of  which  may  be  either  central  or  eccentric. 

For  the  study  of  these  cells,  teased  preparations  must  be 
used.  The  spinal  ganglia  of  fish,  particularly  of  the  roach 
and  pike,  the  Gasserian  ganglion  of  the  frog,  or  the  ganglion 


BY    DR.    KLEIN.  83 

through  which  in  the  same  animal  the  auditory  nerve  passes — 
are  best  suited  for  the  purpose.  If  the  first  are  used,  the  root 
of  the  nerve  with  its  ganglion  is  excised,  and  macerated  in 
iodized  serum,  dilute  solution  of  bichromate  of  potash,  or 
Miiller's  fluid,  for  twenty-four  hours  or  more,  after  which  the 
cells  may  be  teased  out  with  needles.  Good  teased  prepa- 
rations can  also  be  obtained  of  the  ganglia  of  the  spinal 
nerves  of  fish  or  frogs  in  the  fresh  state.  The  ganglion  cells 
of  fish  and  frogs,  thus  isolated,  are  mostly  bipolar,  less  fre- 
quently multipolar.  The  processes  exhibit  fibrillar  streaking, 
and,  when  a  process  is  isolated  for  some  distance,  it  is  found 
to  become  invested  with  a  medullary  sheath  at  a  short  distance 
from  its  origin  ;  or,  in  other  words,  it  assumes  the  characters 
of  a  medullated  nerve  fibre.  The  Schwann's  sheath  of  this 
nerve  fibre  is  continuous  with  the  similar  membrane  which 
forms  the  capsule  of  the  ganglion  cells  from  which  it  originates, 
and  in  which,  as  in  the  Schwann's  sheath,  there  are  oblong 
nuclei  at  regular  distances.  In  the  ganglion  cells  of  the  Gas- 
serian  ganglion  of  the  frog,  there  are  always  masses  of  yellow 
pigment.  In  the  spinal  nerve  ganglia  of  the  mammalia,  it  is 
only  possible  to  isolate  unipolar  cells.  Good  permanent  pre- 
parations of  ganglion  cells  may  be  obtained  after  treatment 
with  chloride  of  gold.  With  this  view  the  Gasserian  ganglion 
of  the  frog,  freshly  excised  and  cut  into  with  fine  scissors,  is 
placed  for  ten  or  fifteen  minutes  in  chloride  of  gold,  and  then 
exposed  in  slightly  acidulated  water  to  daylight,  until  it  as- 
sumes a  darkish  tinge.  In  preparations  of  ganglia  thus  treated 
and  teased  in  glycerin,  the  ganglion  cell  substance,  along 
with  the  axis-cylinder  process,  is  violet  red,  while  the  nucleus 
is  pale.1 

(b)  Ganglion  Cells  of  the  Brain  and  Spinal  Cord. — 
The  spinal  cord  of  the  calf  or  ox  are  the  best  objects  for  this 
demonstration.  The  organ  must  be  divided  into  small  por- 
tions, which  must  be  placed  in  bichromate  of  potash  solution, 
for  periods  varying  from  a  few  da}Ts  to  several  weeks.  Then 
a  thin  slice  of  gray  substance  is  to  be  cut  with  the  razor — pre- 
ferably from  the  anterior  horns — and  teased  in  the  liquid  in 
which  it  has  been  macerated.     Any  one  who  is  practised  in  the 

1  Preparation  of  the  Gasserian  Ganglion. — A  frog  having  been 
rendered  ex-sanguine  by  slitting  open  the  ventricle,  the  roof  of  the 
skull  is  exposed,  and  then  carefully  raised  from  the  occipital  region  for- 
wards. This  process  is  continued  until  the  internal  auricular  foramen 
of  the  petrous  bone  can  be  distinctly  seen.  Then  the  medulla  oblon- 
gata and  pons  are  pushed  aside  with  a  needle,  and  the  notch  of  the 
pars  petrosa  cleared  of  fluid  by  dabbing  it  with  a  fragment  of  bibulous 
paper.  The  fifth  nerve  is  then  readily  seen.  On  it,  close  to  where  it 
enters  the  bone,  is  a  distinctly  yellow  swelling,  which  must  be  care- 
fully exposed  by  removing  the  portion  of  bone  which  conceals  it,  and 
excised  with  fine  scissors. 


#4  TISSUES   OF   THE   NERVOUS   SYSTEM. 

use  of  the  needle  can  also  obtain  good  preparations  by  teasing 
from  fresh  spinal  cords,  in  iodized  serum.  In  preparations  of 
this  kind,  in  addition  to  the  multipolar  ganglion  cells,  mednl- 
lated  nerve  fibres,  of  various  diameters,  possessed  of  irregular 
or  regular  dilatations  (varicosities),  and  axis-cylinders  of  va- 
rious size  with  distinct  fibrillar  streaking,  are  to  be  met  with. 
In  teasing  spinal-cord  preparations,  it  is  always  well  to  place 
the  glass  on  a  black  ground. 

The  ganglion  cells  of  the  anterior  horns  of  the  spinal  cord 
of  the  calf  are  remarkable  for  their  size,  and  consist  of  a 
granular  cell  substance,  in  which  (as  may  be  seen  in  prepara- 
tions in  iodized  serum  under  very  high  powers)  fibrils  may  be 
distinguished.  The  large  round  vesicular  nucleus  which  each 
cell  contains,  has  a  double  contour,  and  incloses  a  highly 
refractive  nucleolus:  in  its  neighborhood  there  is  usually  a 
mass  of  pigment.  Each  cell  possesses  processes  of  two  kinds — 
the  so-called  axis-cylinder  process,  and  the  branched  processes. 
The  axis-cylinder  process  springs  from  a  broad  base,  from 
which  it  tapers  to  a  fine  filament.  To  whatever  distance  this 
filament  is  traced,  it  is  seen  that  it  it  does  not  branch,  but 
becomes  thicker,  and  eventually  assumes  the  character  of  a 
medullated  nerve  fibre.  The  other  processes  are  broad  and 
flattened,  and  soon  divide  dentritically.  They  consist  of  fibrils 
embedded  in  a  coarsely  granular  interstitial  substance:  the 
fibrils  can  be  followed  distinctly  into  the  ganglion  cell.  As 
we  shall  see  subsequently,  the  terminations  of  these  processes 
form  a  dense  network  of  extremely  minute  filaments,  which 
network  is  in  equally  direct  continuity  with  the  endings  of 
the  nerve  fibres  which  enter  the  cord  by  the  posterior  roots. 
The  cells  of  the  posterior  horns  are  entirely  similar,  but  some- 
what smaller.  If  thin  sections  of  the  spinal  cord  of  the  pike 
are  hardened  in  bichromate  of  potash  or  chromic  acid,  washed 
in  water  for  twenty-four  to  forty-eight  hours,  and  then  placed 
in  diluted  ammoniacal  solution  of  carmine  for  a  few  hours  or 
a  day,  good  permanent  preparations  can  be  obtained  by  teasing, 
which  can  be  mounted  in  glycerin.  In  the  nuclei  of  Stilling, 
in  the  intra-cranial  part  of  the  cord,  cells  occur  resembling 
those  of  the  anterior  horn  of  the  spinal  cord,  and  may  be  pre- 
pared in  the  same  way. 

Gerlach's  method  of  demonstrating  the  relation 
between  the  ganglion  cells  and  the  network  of  non- 
medullated  nerve  fibres  in  the  spinal  cord. — Longi- 
tudinal sections,  which  must  be  as  thin  as  possible,  are  made 
through  the  anterior  horns  of  the  gray  substance  of  a  per- 
fectly fresh  spinal  cord  of  the  calf  or  ox ;  these  are  transferred 
as  they  are  cut  into  very  dilute  solution  of  bichromate  of 
potash  (one  part  in  5,000-10,000),  and  allowed  to  remain  for 
two  or  three  days  in  a  cool  place.     Thereupon  they  are  placed 


BY    DR.    KLEIN.  85 

for  twenty-four  hours  in  very  dilute  solution  of  carmine;  they 
are  then  washed  in  distilled  water,  teased  out- superficially  on 
the  object-glass,  and  mounted  in  glycerin.  I  have  also  found 
it  possible  to  demonstrate  the  extremely  fine  network  of  non- 
medullated  nerve  fibres,  with  the  greatest  distinctness,  in 
teased  preparations  of  sections  of  the  gray  substance  of  the 
spinal  cord  of  the  calf,  after  maceration  for  two  or  three  weeks 
in  one  per  cent,  solution  of  bichromate  of  potash. 

Ganglion  Cells  of  the  Hemispheres. — If  the  cortical 
substance  of  the  mammalian  brain  be  macerated  in  iodized 
serum,  bichromate  of  potash,  or  Midler's  fluid,  ganglion  cells 
of  more  or  less  conical  form  can  be  isolated,  from  the  base  of 
each  of  which  several  arborescent  processes  stretch  inwards 
towards  the  white  substance,  while  the  small  end  of  the  cone 
terminates  in  a  process  which  is  simple  near  its  origin,  but 
eventually  divides  into  fine  branches,  and  exhibits  everywhere 
(in  iodized  serum  preparations)  fibrillar  streaking.  Permanent 
teased  preparations  may  be  obtained  in  the  way  described 
above  as  applicable  to  the  spinal  cord. 

(c)  Ganglion  Cells  of  the  Sympathetic  System. — 
The  ganglion  cells  of  the  sympathetic  system  occur  either  as 
distinct  ganglia  of  various  size  (as  is  seen  in  the  digestive 
mucous  tracts,  and  in  the  genital  organs),  or  they  are  ar- 
ranged in  linear  series,  or  are  scattered  in  greater  or  less 
number  amongst  and  between  the  fibres  of  nerves.  The  sym- 
pathetic ganglia  (as,  for  example,  those  of  the  ganglionic  cord 
or  the  coeliac  ganglion  of  mammalia)  are  best  studied  as  fol- 
lows :  The  structure  is  placed  in  Midler's  fluid  or  bichromate 
of  potash,  and  allowed  to  remain  several  days  until  firm 
enough.  Fine  sections  are  then  prepared,  and  teased  in  gly- 
cerin, either  at  once  or  after  staining  in  solution  of  carmine. 
Another  plan  consists  in  steeping  sections  prepared  from 
frozen  ganglia,  in  chloride  of  gold  for  ten  or  fifteen  minutes, 
and  making  from  them  teased  preparations,  which  may  be 
mounted  in  glycerin.  Again,  small  fragments  of  fresh  ganglia 
may  be  steeped  in  one-tenth  to  one  and  a  half  per  cent,  acetic 
acid,  and  left  in  it  from  twenty-four  to  forty-eight  hours,  and 
then  employed  in  the  same  way. 

The  aorta  and  the  bulbus  arteriosus  of  the  frog  afford  excel- 
lent preparations.  For  this  purpose  the  vessel  is  ligatured  at 
the  point  of  division,  and  filled  with  half  per  cent,  solution  of 
chloride  of  gold  by  aid  of  a  capillary  tube.  A  second  ligature 
having  been  placed  around  the  bulb,  the  part  is  cut  out,  and 
steeped  for  ten  minutes  in  the  same  solution.  The  tube  is 
then  opened  and  exposed,  two  days  or  more,  in  acidulated 
water,  to  the  light.  When  of  sufficiently  dark  color,  it  is 
stuck  out  on  a  cork  with  pins.     Thin  lamella?  may  then  be 


86  TISSUES   OF   THE   NERVOUS   SYSTEM. 

stripped  off  the  external  aspect  of  the  vessel,  spread  out  on  an 
object-glass,  and  covered  in  glycerin. 

Meissner's  Plexus. — The  ganglionic  nodules,  occurring 
in  the  course  of  the  nerves  which  form  Meissner's  plexus,  in 
the  submucosa  of  the  intestine,  may  be  studied  as  follows. 
They  are  also  well  seen  in  longitudinal  and  cross  sections  of 
intestine  hardened  in  chromic  acid,  and  still  better  in  sections 
parallel  with  the  surface.  Strips  of  intestine  of  the  cat  or  clog 
(after  having  been  washed  with  half  per  cent,  salt  solution,  or 
water  colored  slightly  with  bichromate  of  potash)  are  steeped 
for  from  forty  minutes  to  an  hour  in  half  per  cent,  gold  solu- 
tion, and  then  exposed  to  light  in  distilled  water,  and  finall}' 
hardened  in  alcohol.  Sections  are  then  made  in  a  direction 
parallel  to  the  serosa,  of  which  of  course  those  only  are  of 
use  which  pass  through  the  submucous  tissue.  Any  one  pos- 
sessed of  sufficient  dexterity  can  obtain  good  preparations  by 
spreading  bits  of  rabbit's  intestine,  excised  and  cleansed  as 
above  described,  on  a  piece  of  cork  by  aid  of  pins,  with  the 
mucous  surface  uppermost.  The  mucosa  is  then  Avorked  off 
as  completely  as  possible  with  the  fine-pointed  forceps.  Fine 
flakes  of  loose  tissue  must  be  snipped  with  the  aid  of  the 
curved  scissors,  either  from  the  deep  surface  of  the  mucosa,  or 
from  the  surface  from  which  it  has  been  severed.  These  are 
either  examined  in  salt  solution  in  the  fresh  state,  or  treated 
with  gold  for  permanent  preparations. 

Auerbach's  Ganglia. — The  ganglia  of  Auerbach,  which 
are  interposed  between  the  transverse  and  longitudinal  muscu- 
lar layers,  are  demonstrated  as  follows  :  A  portion  of  fresh  intes- 
tine of  a  rabbit  or  new-born  foetus  is  blown  out  with  the  aid  of 
a  glass  tube.  The  operator  must  then  try  to  strip  off  with  the 
forceps,  from  the  external  surface,  a  thin  membrane,  which  will 
be  found  to  contain  the  serosa  and  the  longitudinal  muscular 
layer.  Strips  of  considerable  extent  ma}'  be  thus  obtained  with 
a  little  practice,  and  must  be  then  treated  with  gold  in  the 
usual  manner. 

The  ganglion  cells,  which  occur  in  the  genital  organs,  may 
be  best  studied  in  sections  or  parts  hardened  in  chromic  acid, 
or  colored  with  gold  and  then  hardened  in  alcohol. — Good 
preparations  of  sympathetic  ganglia  can  be  obtained  from  the 
bladder  of  the  rabbit.  Bits  of  the  fresh  bladder  are  colored 
with  chloride  of  gold,  and  then  steeped  in  acidulated  water  until 
they  swell  out  into  a  gelatinous  translucent  mass.  Thin  mem- 
branous fragments  stripped  off  with  the  forceps,  or  snipped  off 
with  the  scissors,  are  spread  out  and  covered  in  glycerin.  To 
these  preparations  we  shall  recur,  in  connection  with  the  dis- 
tribution of  the  nerves  among  unstriped  muscular  fibres. 

Intimate  Structure  of  the  Ganglion  Cells  of  the 
Sympathetic  System.— In  each  ganglion  cell  (with  the  ex- 


BY   DR.    KLEIN.  87 

ception  of  those  of  the  ganglia  of  Auerbach)  the  following  parts 
may  be  distinguished  ;  the  capsule,  the  body  of  the  cell  and  its 
nucleus,  aud  the  processes.  The  capsule  is  beset  with  strong  nu- 
clei at  even  distances  from  each  other  ;  in  sections  of  fresh  gan- 
glia hardened  by  freezing,  and  treated  with  nitrate  of  silver, 
markings  may  be  seen  in  the  capsule  which  indicate  the  exist- 
ence of  endothelium  ;  the  elements  of  this  endothelium  are  of 
such  size  as  to  make  it  apparent  that  each  of  the  nuclei  above 
mentioned  belong  to  an  individual  cell.  As  in  the  ganglia  of  the 
spinal  nerves,  the  capsule  is  continued  from  the  cell  upon  one 
of  the  processes,  with  the  Schwann's  sheath  of  which  it  becomes 
identified.  The  ganglion  cells  of  the  sympathetic  system  are 
of  various  size,  and  are  either  globular  or  oblong.  In  the  for- 
mer case,  they  may  be  either  without  distinguishable  processes, 
or  may  have  a  single  process  (unipolar),  or  two  in  opposite 
directions  (bipolar)  ;  being  in  the  former  case  pear-shaped,  in 
the  latter  spindle-shaped.  Others  occur  which  have  two  pro- 
cesses in  the  same  direction,  or  numerous  processes  in  various 
directions  (multipolar  cells).  The  substance  of  the  ganglion 
cell  is  for  the  most  part  finely  granular,  sometimes  containing 
clumps  of  pigment  of  various  size.  Each  cell  contains  a  single 
vesicular  nucleus  (or  two  nuclei),  which  is  usually  eccentric, 
and  always  contains  a  large,  shining  nucleolus.  In  the  exami- 
nation of  a  number  of  ganglion  cells,  one  or  two  can  generally 
be  found  in  which  fine  fibrils  are  distinguishable :  these  can 
often  be  traced  nearly  to  the  nucleus,  presenting  an  appearance 
which  seems  to  correspond  with  the  network  of  fibres  described 
by  some  in  the  body  of  the  cells. 

Spiral  Fibre  Cells. — In  the  cells  of  the  sympathetic  gan- 
glia of  the  frog,  as  well  as  of  the  coeliac  ganglion  of  mammalia, 
and  in  those  of  the  bladder  of  the  rabbit,  pear-shaped  or  club- 
shaped  ganglion  cells  may  be  isolated,  which  possess  two  pro- 
cesses, extending  in  the  same  direction.  These  processes  differ 
more  or  less  in  thickness  from  each  other :  they  are  contained 
near  their  origin  in  a  common  sheath,  which,  at  a  greater 
distance,  divides  into  two,  each  investing  one  of  the  processes. 
So  long  as  they  are  in  the  common  sheath,  their  arrangement 
to  one  another  is  peculiar.  Sometimes  they  merely  cross  one 
another;  at  others,  one  of  them,  usually  the  thinner,  twines 
spirally  round  the  other.  Occasionally,  this  last  is  perfectly 
straight ;  sometimes  it  is  apparently  of  the  same  substance  with 
the  body  of  the  cell ;  at  others,  it  seems  to  penetrate  into  its  in- 
terior tending  towards  the  nucleus,  without,  however,  being  de- 
monstrably united  with  it.  The  second  process,  viz.,  the  so- 
called  spiral  fibre,  originates  by  a  double  or  single  root,  which 
can  be  followed  to  certain  nucleolus-like  structures,  of  oblong 
form,  of  which  from  one  to  four  are  to  be  found  in  the  neighbor- 
hood of  the  pole  from  which  the  straight  process  springs.     But 


88  TISSUES   OF   THE    NERVOUS    SYSTEM. 

whether  the  spiral  fibre  is  connected  with  these  nuclei,  as  hns 
been  supposed,  by  a  network  of  extremely  fine  filaments  from 
which  it  appears  to  spring,  cannot  be  determined  any  more 
certainly  than  the  question  whether,  in  multipolar  cells  in  gene- 
ral, the  processes  spring  entirely  from  the  substance  of  the  cell, 
or  one  or  other  of  them  from  the  nucleus. 

Reproduction  of  Ganglion  Cells. — The  ganglion  cells  of 
the  sympathetic  system  seem  to  undergo  very  active  develop- 
ment. This  appears,  first,  from  the  frequency  with  which  cells 
containing  two  nuclei  are  met  with ;  secondl}',  from  the  cir- 
cumstance that  frequently  two,  three,  or  four  polyhedral  cells 
occur  in  a  common  capsule;  thirdly,  from  the  occasional  oc- 
currence of  two  club-shaped  cells  in  one  capsule,  so  placed  that 
they  are  in  apposition  by  their  flat  bases,  while  their  sharp 
ends  are  continuous  with  processes;  and  finally,  that  in  many 
organs,  as,  e.  </.,  in  the  (male)  genital  tract,  and  in  Meissner's 
ganglia  of  the  newly-born  foetus,  groups  (so-called  "  nests")  of 
extraordinarily  small  ganglion  cells  occur.  If  the  Auerbach's 
ganglia  of  the  rabbit's  intestine  are  prepared  as  directed  above, 
and  covered  in  serum,  they  are  found  to  consist  of  a  network 
of  bands  of  various  breadth,  the  nodes  of  which  constitute 
broad  plates  of  irregular  form,  the  whole  being  invested  by  a 
sheathing  in  which  nucleus-like  structures  are  distinguishable. 
The  substance  both  of  the  nodes  and  of  the  bands  which  connect 
them  is  finely  streaked  or  granular.  A  greater  or  less  number 
of  ganglion  cells  mostly  globular  inform,  are  embedded  in  this 
substance,  and  arranged  either  in  groups  (in  the  nodes)  or  in 
rows  (in  the  bands).  In  the  latter,  the  chains  of  cells  are  inter- 
rupted at  intervals;  the  former  exhibit  numerous  perforations, 
which  are  merely  the  interstices  of  a  dense  meshwork  of  bands. 
In  gold  preparations,  these  facts  can  also  be  easily  demon- 
strated. 

In  preparations  made  in  the  same  manner  from  the  intestine 
of  a  nearly  mature  human  embryo,  it  is  possible  to  make  out 
that,  in  the  reticular  sj'stcm  above  described,  numerous  small 
cellular  structures  occur,  embedded  in  the  substance  both  of 
the  bands  and  nodes,  in  most  of  which  all  that  can  be  seen  is  a 
nucleus  surrounded  by  a  very  narrow  entourage  of  granular 
substance:  a  few  present  the  ordinary  characters  of  ganglion 
cells. 

In  sections  of  intestine  of  the  rabbit  hardened  in  chromic 
acid  (as  we  shall  see  in  Part  II.),  the  connection  of  these  gan- 
glia with  the  ganglionic  masses  of  similar  form  which  exist  in  the 
circular  fibres,  and  communicate  towards  the  mucosa  with  the 
ganglia  of  Meissner,  can  be  well  seen. 


BY    DR.    KLEIN.  89 

Section  III. — Peripheral  Nerve  Endings. 

Terminal  Organs  of  Nerve  Fibres.— Pacinian  Bod- 
ies.— The  Pacinian  bodies  are  oval  or  pear-shaped  little  mas- 
ses which  are  found  in  the  subcutaneous  tissue  of  the  skin  of 
the  finger,  and  in  that  of  the  beak  and  tongue  in  birds  (goose 
and  duck).  In  man  they  are  met  with  also  in  the  genital  tract, 
e.  gr.,  in  the  labia  majora,  prostate,  and  corpora  cavernosa :  in 
all  these  situations  they  can  be  best  studied  in  sections.  They 
are  most  easily  demonstrated,  however,  in  the  mesentery  of 
the  cat,  in  which  they  are  visible  to  the  naked  eye  as  elliptical, 
transparent  bodies,  occurring  mostly  in  the  fatty  parts.  Pre- 
parations are  made  as  follows :  A  mesentery  of  a  cat  that 
has  just  been  killed  is  spread  out  on  an  object-glass  and  cov- 
ered with  a  drop  of  serum  or  half  per  cent,  solution  of  common 
salt;  or  a  portion  of  mesentery  containing  Pacinian  bodies  is 
placed  in  solution  of  bichromate  of  potash  for  twenty-four 
hours,  and  then  covered  in  glycerine.  We  begin  our  study 
with  the  medullated  nerve  fibre,  which  enters  the  corpuscle  at 
one  end.  From  the  point  at  which  the  nerve  parts  from  the 
twig  from  which  it  is  a  branch,  its  course  is  winding.  As  it 
approaches  the  Pacinian  body  its  sheath  becomes  thicker,  and 
acquires  an  appearance  as  if  it  consisted  of  several  layers  of 
nucleated  membrane.  The  dark-bordered  nerve  fibre  is  sepa- 
rated from  the  sheath  by  a  distinct,  clear  interspace,  into 
which  oblong  nuclei  project  at  regular  distances  from  the  in- 
ternal surface  of  the  sheath,  so  as  to  resemble  an  endothelium. 
The  Pacinian  corpuscle  may  be  divided  into  the  neck  (the 
point  at  which  the  nerve  enters)  and  the  body.  In  the  neck, 
the  lamellae  of  the  Schwann's  sheath  split  repeatedly,  becom- 
ing further  and  further  apart  from  each  other,  so  as  to  form 
the  well-known  concentric  capsules  of  which  the  body  is  con- 
stituted. Each  capsule  is  beset  with  regularly  arranged  flat 
oblong  nuclei ;  and,  in  the  part  of  the  body  which  is  nearest 
the  neck,  each  capsule  communicates  with  its  neighbors  by 
cross  lamelhe,  which  run  obliquely  from  one  to  the  other. 
Elsewhere  the  capsules  are  discontinuous.  In  the  neck,  the 
nerve  fibre  is  dark-bordered  and  convoluted,  but  as  it  enters 
the  clear  space  which  is  contained  in'  the  inmost  capsule  it 
becomes  straight,  and  at  the  same  time  pale  and  finely  streaked. 
In  its  course  in  the  axis  of  this  space  it  is  separated  from  the 
capsule  by  a  clear  interval,  into  which  nuclei,  arranged  at 
regular  distances,  project.  Near  the  end  of  the  axial  space 
the  nerve  fibre  usually  divides  into  two,  occasionally  into 
three,  branches,  each  of  which  ends  in  a  pear-shaped  enlarge- 
ment (cell),  containing  a  vesicular  nucleus.  Sometimes  the 
nerve  fibre  remains  undivided,  in  which  case  the  terminal  cell 
is  relatively  larger.     In  the  mesentery  of  the  cat  I  have  seen 


90  TISSUES    OF    THE   NERVOUS    SYSTEM. 

Pacinian  corpuscles  in  which  the  nerve  fibre,  instead  of  termi- 
nating, passed  out  at  the  end  opposite  to  that  at  which  it 
entered,  eventually  ending  in  another  Pacinian  body.  In  this 
case  the  relation  of  the  nerve  fibre  to  the  concentric  capsules, 
and  of  these  to  each  other,  in  the  neighborhood  of  the  point 
of  exit  of  the  nerve,  was  the  same  as  in  the  neck.  In  the 
most  superficial  of  the  concentric  capsules,  endothelial  mark- 
ing can  be  seen  after  treatment  with  nitrate  of  silver. 

In  connection  with  the  Pacinian  corpuscles  we  must  mention 
the  so-called  "  Endkolben"  (club-shaped  endings),  which  are 
described  in  the  papillae  of  certain  mucous  membranes,  and 
are  said  to  consist  of  an  axis-cylinder,  ending  in  an  enlarge- 
ment, surrounded  by  a  thickened  sheath. 

Meissner's  Bodies,  or  Tactile  Corpuscles. — These 
bodies  occur  in  certain  broad  papillae  of  the  skin  of  the  volar 
side  of  the  fingers  and  of  the  palm  in  man.  The}'  can  be  best 
demonstrated  in  vertical  sections  of  portions  of  skin,  made 
across  the  parallel  furrows,  and  either  hardened  in  chromic 
acid  or  in  alcohol  after  treatment  with  gold.  They  are  oblong 
bodies,  each  occupying  the  axis  of  a  papilla.  Their  outline  is 
often  broken  by  deep  notches.  In  each  corpuscle  numerous 
cross  markings  are  to  be  seen,  which  depend  partly  on  the 
existence  of  fine  fibres,  partly  on  the  arrangement  of  spindle- 
shaped  nuclei.  Into  each  body  a  medullated  nerve  fibre,  pro- 
vided with  a  nucleated  Schwann's  sheath,  finds  its  way,  and 
then  twines  once  or  twice  round  it :  the  nerve  may  often  be 
followed  to  its  upper  extremity.  Sometimes  the  fibre  appears 
to  enter  the  corpuscle  from  one  side,  in  which  case  it  cannot 
be  traced  further. 

Peripheral  Nerve  Cells. — Fresh  thin  portions  of  human 
skin  (e.  g.,  skin  of  the  prepuce  or  of  amputated  extremities),  or 
small  portions  of  the  shaven  skin  of  the  rabbit's  abdomen,  are 
placed  for  a  few  minutes  in  half  per  cent,  acetic  acid,  and  then, 
after  immersion  for  one  or  two  hours  in  solution  of  chloride 
of  gold,  are  treated  in  the  usual  wa}\  In  sections  of  such  skin, 
fine  nerve  fibres  present  themselves,  which,  after  penetrating 
the  rete  malpighianum,  are  seen  to  be  connected  with  bodies  of 
an  oblong  or  stellate  form,  which  are  strongly  stained  03- gold, 
and  often  contain  each  a  distinct,  clear,  nucleus-like  structure. 
These  nerve  cells  are  not  really,  as  has  been  supposed,  terminal 
organs,  for  fine  fibres  are  seen  not  only  to  reach  them,  but  to 
pass  beyond  them,  towards  the  surface.  Similar  nerve  cells 
exist  in  the  epithelium  of  the  mucous  membrane  of  the  mouth 
and  of  the  vagina.  Again,  in  the  network  of  delicate  non-rae- 
dullated  fibres  which  branch  under  the  epithelium  of  the  tail- 
pole's  tail,  the  nerve  fibres  are  continuous  with  the  processes 
of  branched  nerve-cells. 

Recently,  terminal  bodies  have  been  discovered  by  certain 


BY    DR.    KLEIN.  91 

authors  in  the  mucous  membrane  of  the  epiglottis,  from  which 
it  would  appear  that  nerve  fibres,  either  medullated  or  others, 
end  under  the  epithelium  in  club-shaped  bodies,  consisting  of 
granulous  substance,  each  of  which  contains  one  or  two  nuclei, 
and  is  inclosed  in  a  prolongation  of  the  Schwann's  sheath  of 
the  nerve.  In  the  mucous  membrane  of  the  frog's  stomach  it 
is  also  stated  that  the  nerve  fibres  end  between  the  cylindrical 
elements  of  the  epithelium  in  oval  or  club-shaped  swellings. 
Again,  in  the  connective  tissue  of  the  bladder  of  the  frog,  are 
to  be  found  cells  which  consist  of  a  fine  granulous  protoplasm, 
and  contain  several  nuclei.  In  the  skin  of  the  wing  of  the  bat, 
and  in  the  skin  of  the  ears  of  mice,  the  medullated  nerves  come, 
at  certain  parts,  into  remarkable  relation  with  the  papillae  of 
the  hairs  (See  Chapter  XI.). 

Peripheral  Branching  of  the  Non-Medullated 
Nerve  Fibres  in  Different  Tissues. — Under  this  head 
will  be  described  the  termination  of  the  nerves  in  the  cornea, 
conjunctiva,  in  the  tail  of  the  tadpole,  in  the  skin  in  certain 
mucous  membranes,  in  unstriped  muscular  fibres,  in  striped 
muscular  fibres,  in  bloodvessels,  and  in  glands.  The  nerve 
endings  of  organs  of  special  sense  will  be  described  hereafter. 

Nerves  of  the  Cornea. — In  a  living  or  recently  killed 
rabbit,  the  cornea  is  excised  close  to  the  limbus,  and  placed  in 
chloride  of  gold  solution  for  three-quarters  of  an  hour.  The 
preparation  is  then  transferred  to  distilled  water,  in  which  it 
remains  until  it  has  attained  a  steel-gray  color,  the  time  re- 
quired varying,  according  to  the  season,  from  six  hours  to  six- 
teen or  twenty.  Thence  the  object  is  transferred  to  a  small 
wide-mouthed  vessel,  which  contains  a  small  quantity  of  nearly- 
concentrated,  filtered  solution  of  tartaric  acid.  As  soon  as  it 
has  had  time  to  absorb  the  liquid,  its  color  becomes  deeper, 
and  changes  to  grayish-violet.  If  the  bottle  is  then  plunged 
into  water  at  a  temperature  of  40°  to  50°  C,  to  such  a  depth 
that  both  liquids  stand  at  the  same  level,  the  preparation  as- 
sumes, after  a  few  minutes,  an  intense  violet-red  color,  which 
goes  on  increasing  until  it  attains  a  dirty  brownish-red,  and 
exhibits  a  velvety  lustre.  The  cornea  is  now  removed,  and 
steeped  in  distilled  water  for  two  hours  or  more.  The  epithe- 
lium, along  with  a  thin  layer  of  corneal  substance,  is  then 
stripped  off  with  the  aid  of  the  pointed  forceps,  beginning  from 
the  sclerotic  beyond  the  edge.  In  a  preparation  thus  obtained, 
it  is  seen  that  there  exists  in  the  anterior,  i.  e.  most  superficial, 
layer  of  the  cornea  propria,  a  plexus  of  nerves  of  various 
breadth  ;  each  of  these  nerves  consists  of  a  bundle  of  minute 
fibrils,  invested  in  a  pale  Schwann's  sheath  with  oblong  nuclei, 
within  which  they  may  either  run  parallel  to  each  other,  or  wind 
round  each  other  in  a  more  or  less  spiral  manner.  Wherever 
a  bifurcation  occurs,  or  two  nerves  join,  there  is  an  enlarge- 


92  TISSUES   OF   THE   NERVOUS   SYSTEM. 

ment,  in  which  the  individual  fibrils  are  distinct^'  woven  to- 
gether into  a  network.  From  the  nerves  of  this  plexus,  fibriH 
are  given  off  either  alone  or  in  tufts.  Their  general  direction 
is  towards  the  surface.  In  taking  this  course  they  divide  into 
finer  and  finer  filaments,  so  that  the  finest  are  scarcely  dis- 
tinguishable under  the  highest  powers,  and  form,  by  repeated 
anastomoses,  a  network  which  lies  immediately  under  the  epi- 
thelium. The  fibrils  themselves  are  beset  with  minute  granu- 
lar varicosities.  In  either  case  these  form  a  network,  the 
meshes  of  which  are  oblong  or  quadrangular.  Corneas  pre- 
pared in  the  manner  above  described  may  be  also  advanta- 
geously employed  for  the  preparation  of  vertical  and  horizontal 
sections. 

The  nerves  of  the  substantia  propria  of  the  cornea  of  the 
frog  are  best  demonstrated  as  follows:  A  silk  thread  having 
been  passed  through  the  centre  of  the  cornea  of  rana  esculenta 
and  brought  out  again  at  the  sclerotic  ring,  the  two  ends  are 
knotted  together.  After  the  thread  has  remained  from  five  to 
eight  hours,  the  cornea  is  excised  and  placed  for  twenty  min- 
utes or  more  in  half  per  cent,  solution  of  chloride  of  gold.  It 
is  then  transferred  to  distilled  water,  and  exposed  to  light  until 
it  acquires  a  dark  violet-red,  or  reddish-brown  color;  the  time 
required  for  this  purpose  varying  from  one  to  three  days,  ac- 
cording to  the  season.  The  epithelium  must  now  be  removed 
with  the  aid  of  sharp-pointed  forceps,  along  with  a  very  thin 
layer  of  corneal  tissue,  after  which  the  cornea  is  to  be  mounted 
in  glycerin.  In  such  a  preparation  it  is  seen  that  the  nerve 
trunks  form  a  rich  plexus  by  division  and  anastomosis  in  the 
corneal  substance.  The  branches  of  this  plexus  may  be  dis- 
tinguished as  nerves  or  bundles  of  the  first  order,  and  resemble 
in  their  structure  the  corresponding  nerves  already  described  in 
the  cornea  of  the  rabbit.  From  these,  smaller  bundles,  not  pos- 
sessed of  a  nucleated  sheath  (nerves  of  the  second  order)  are 
given  off.  These  run  a  course  which  is  sometimes  winding, 
sometimes  straight,  and  are  connected  by  scanty  anastomoses, 
so  as  to  form  a  plexus  of  large  meshes.  The}'  give  off,  either 
laterall}'  or  terminally,  the  fibrils  of  the  third  order. 

Nerves  of  the  Conjunctiva  and  Membrana  Nicti- 
tans. — For  the  study  of  the  nerves  of  the  mammalian  conjunc- 
tiva, the  conjunctiva  fornicis,  or  the  plica  semiluna?'is  of  the 
eye  of  the  pig,  calf,  or  rabbit  answers  best.  Portions  of  the  fresh 
plica  semilunaris  are  treated  in  the  same  way  as  the  cornea  of 
the  rabbit.  As  soon  as  the  proper  degree  of  coloration  is  at- 
tained, the  preparation  is  hardened  in  diluted  alcohol.  Sec- 
tions are  then  made  in  both  directions,  and  covered  in  glycerin. 
The  conjunctiva  fornicis  is  prepared  free  over  a  considerable 
surface,  and  spread  out  on  a  cork  with  the  free  surface  up- 
wards.    It  may  then  be  immersed  in  gold  solution  in  a  cup- 


BY    DR.    KLEIN.  93 

sule,  or  this  liquid  may  be  poured  on  it,  after  which  it  must 
be  treated  as  before.  The  demonstration  of  the  fine  nerves  of 
the  conjunctiva  is  not  so  easy  as  of  those  of  the  cornea,  so  that 
a  general  idea  of  their  distribution  can  only  be  obtained  by  a 
comparison  of  a  number  of  preparations.  The  nerve  trunks, 
composed  of  medullated  fibres,  divide  in  the  superficial  layer 
of  the  mucosa  into  small  branches,  each  containing  two  or 
three  medullated  fibres,  in  which  varicosities  occur  here  and 
there.  These  mostly  accompany  bloodvessels,  following  a 
winding  course,  and,  by  their  communications,  forming  a  plex- 
us. They  give  off  under  the  epithelium  non-medullated  fibres, 
by  the  anastomosis  of  which  a  scanty  sub-epithelial  network 
is  formed.  I  have  seen  fibres  originating  from  this  network 
making  their  way  towards  the  surface  among  the  epithelium 
cells,  and  dividing  dichotomously,  but  have  been  unable  to 
trace  their  further  course. 

The  mode  of  preparing  the  membrana  nictitans  is  the  same 
as  that  for  the  cornea.  The  fresh  membrane  is  placed  for 
twenty  minutes  in  chloride  of  gold,  and  then  in  distilled  water 
until  it  is  of  a  dark  color.  The  epithelium  of  the  anterior  sur- 
face is  then  stripped  off  with  the  sharp-pointed  forceps,  after 
which  the  preparation  is  covered  in  glycerin.  The  objects 
which  present  themselves  are  (1)  The  flask-shaped  glands  (with 
their  short,  narrow  ducts)  lined  with  spheroidal,  granular,  nu- 
cleated cells  ;  they  are  surrounded  by  a  layer  of  spindle-shaped 
cells,  not  unlike  muscle-cells.  (2)  Granular,  large,  flat,  branched 
cells,  brightly  stained,  possessing  oblong,  flat  nuclei,  and  send- 
ing out  processes  which  communicate  in  the  same  way  as  cor- 
nea corpuscles.  (3)  Pigment  cells,  some  of  which  are  much 
branched  and  communicate  with  each  other,  while  others  are 
isolated  and  clump-shaped.  (4)  A  rich  network  of  bloodves- 
sels. (5)  Nerves.  From  the  plexus  of  medullated  nerves, 
separate  medullated  nerve  fibres  spring,  which,  close  to  their 
origin,  lose  their  medullaiy  sheaths.  The  non-medullated 
fibres  possess  numerous  oblong  nuclei. 

Nerves  of  the  Skin. — We  have  already  had  occasion  to 
describe  the  method  of  preparation  to  be  adopted  for  the  study 
of  the  nerves  in  the  skin.  It  may,  however,  be  well  to  add 
that,  immediately  after  removing  the  preparation  from  the 
gold  solution,  it  is  possible  to  cut  sections.  The  nerve  trunks, 
which  find  their  way  from  the  subcutaneous  tissue  towards 
the  epidermis,  unite  at  the  surface  of  the  corium  to  form  a 
dense  network  of  non-medullated  fibres,  from  which  fine  fibrils 
stretch  vertically  into  the  rete  Malpighii  either  as  isolated 
fibrils  which  pass  up  into  the  epithelium  between  two  neigh- 
boring papillae,  or  as  groups  of  several  fibrils  which  pierce  the 
tips  of  the  papilhe.  In  the  rele  Malpighii  the  nerve  fibres  often 
divide,  and  occasionally  communicate  with  their  neighbors  by 


94  TISSUES   OF   THE    NERVOUS   SYSTEM. 

horizontal  brandies,  or  with  processes  of  the  deeply  stained 
branched  cells  above  described.  Isolated  fibres  may  be  traced 
in  the  rete  Malpighii  to  within  a  short  distance  of  the  horny 
layer,  where  they  either  seem  to  lose  themselves  in  swellings 
of  various  size,  or  to  divide  dichotomously  beyond  ;  eventually 
returning  towards  the  corium.  The  hair  bulbs  are  also  sur- 
rounded by  a  network  of  fine  non-medullated  nerve  fibres,  the 
further  description  of  which  will  be  found  in  another  part. 

Nerves  of  the  Tadpole's  Tail. — The  best  object  for  the 
purpose  is  the  tadpole  of  Hyla.  The  distribution  to  be  now 
described  may  be  studied  in  recent  preparations  in  half  per 
cent,  salt  solution  or  serum.  It  is,  however,  better  to  make 
preparations  by  the  method  full}'  described  in  the  chapter  on 
connective  tissue.  The  peripheral  nerves  of  the  tadpole's  tail 
are  derived  from  a  plexus  which  lies  immediately  underneath 
the  sub-epithelial  hyaline  layer ;  the  nerves  which  form  it  are 
composed  almost  entirely  of  non-medullated  fibres,  which  are 
invested  in  a  sheath  beset  with  oblong  nuclei.  From  this  plex- 
us similar  fibres  arise  towards  the  epithelium,  and  by  division 
become  smaller  and  smaller,  anastomosing  with  each  other 
so  as  to  form  a  second  plexus  nearer  the  epithelium  than  the 
other.  They  also  possess  nuclei,  the  position  of  which  in  re- 
lation to  the  fibre  is  sometimes  lateral,  sometimes  apparently 
axial.  In  the  more  superficial  plexus,  spindle-shaped  enlarge- 
ments are  frequently  seen  at  equal  distances  from  each  other. 
These  are  distinctly  granular,  and  each  contains  one  oblong, 
clear,  sharply-defined  nucleus,  and  nucleoli.  They  are  to  be 
considered  as  bipolar  ganglion  cells,  occurring  in  the  course 
of  the  fine  non-medullated  fibres.  Immediately  under  the  epi- 
thelium the  densest  branching  of  the  fine,  pale  fibres  is  seen. 
These  bifurcate  repeatedl}*,  displaying  at  tolerably  regular  dis- 
tances, and  especially  at  the  points  of  division,  numerous 
granular  swellings.  The  branchlets  arising  from  this  repeated 
division  join  each  other  archwise,  forming  a  very  close  network, 
the  meshes  of  which  are  round,  or  more  often  polyhedral,  and 
of  such  size  that  two  or  four  of  them  can  be  covered  by  the 
nucleus  of  an  epithelial  cell.  In  this  network,  nuclei  and  cells 
are  scattered,  the  former  being  sharply  defined  and  of  oblong 
or  irregular  shape,  exactly  similar  to  those  mentioned  above 
as  occurring  in  the  fine  non-medullated  fibres.  The  cells  are 
spindle-  or  (more  frequently)  star-shaped,  flat,  and  finely  granu- 
lar, each  containing  a  roundish  nucleus.  Their  short  pointed 
processes  are  in  continuity  with  the  fibres  of  the  nerve  plexus. 
They  may  be  regarded  as  multipolar  ganglion  cells.  (See  p. 
77,  ■'  peripheral  nerve  cells.")  I  could  never  find  any  connec- 
tion between  the  pale  nerve  fibres  and  the  well-known  pale  or 
pigmented  branched  cells  of  the  connective  tissue.  From 
these  facts  we  learn  that  the  fine  nerves  of  the  tadpole's  tail 


BY    DR.    KLEIN.  95 

terminate  close  to  the  epithelium  in  a  dense  network  of  pale 
fibres,  extending  equally  on  both  sides  of  the  tail  so  as  to  form 
a  continuous  sub-epithelial  layer.  As  no  nerve  fibres  can  be 
traced  bej-ond  this  network,  we  are  entitled  to  conclude  that 
the  nerves  terminate  in  it. 

Nerves  of  the  Mucous  and  Serous  Membranes. — 
Thin  strips  of  fresh  mucous  membrane  are  cut  from  the  vagina 
or  mouth  of  the  dog  or  rabbit,  and  are  placed  for  from  forty- 
five  to  sixty  minutes  in  half  per  cent,  solution  of  chloride  of 
gold,  and  are  then,  after  having  been  washed  with  distilled 
water,  transferred  to  a  solution  of  tartaric  acid,  hardened  in 
alcohol,  and  employed  for  the  preparation  of  sections  in  the 
manner  already  explained.  The  nervous  trunks  which  are 
distributed  to  the  mucous  membrane  consist  mostly  of  medul- 
lated  fibres,  and  give  off  branches  which  resolve  themselves 
into  a  network  of  fine  non-medullated  fibres,  lying  immedi- 
ately beneath  the  epithelium,  and  the  films  of  this  network  are 
beset  with  nuclei,  which  are  either  far  apart,  as  in  the  vaginal 
mucous  membrane  of  the  dog,  and  in  the  oral  and  vaginal 
mucous  membrane  of  the  rabbit,  or  more  frequent,  as  in  the 
mouth  of  the  dog.  From  this  network,  filaments  having  vari- 
cosities of  various  sizes,  find  their  way  into  the  epithelium, 
and  give  off  branches  to  the  different  layers  of  epithelium 
which  combine  into  a  network,  some  of  which  appear  to  end 
in  a  knob-like  swelling.  In  the  middle  layers  they  are  in  com- 
munication with  branched  nerve-cells:  there  is  no  evidence 
of  an}r  connection  between  them  and  the  branched  cells  of  the 
mucosa. 

Nerves  of  the  Septum  Cistern®  and  of  the  Mesen- 
tery of  the  Frog  or  Newt. — It  is  comparatively  difficult 
to  demonstrate  non-medullated  nerves  in  these  parts  by  means 
of  the  ordinary  method  of  staining  with  gold.  It  can  be 
done  in  the  following  way  successfully :  The  fresh  membrane 
is  placed  for  from  fort\T-five  to  sixty  minutes  in  solution  of 
gold  ;  thereupon  it  is  exposed  to  the  light  for  several  days  in 
distinctly  acid  water.  As  soon  as  the  preparation  has  ac- 
quired a  markedly  reddish  or  grayish-violet  tint,  it  is  pencilled 
on  both  sides  so  as  to  remove  the  endothelium,  and  placed  for 
ten  minutes  in  diluted,  distinctly  alkaline  solution  of  carmine. 
It  is  then  washed  in  acidulated  water  and  covered  in  glycerin. 
From  the  winding  nervous  trunks  which  accompany  the  larger 
vessels  of  the  mesentery,  numerous  small  twigs  branch  off  in 
great  numbers,  consisting  of  very  numerous  non-medullated 
fibres,  which  combine  to  form  a  network.  Although  these 
fibrils  are  much  more  numerous  than  has  been  hitherto  sup- 
posed, they  never  terminate  by  a  free  end,  but  always  take 
part  in  the  formation  of  a  network.    (The  numerous  non-medul- 


9t>  TISSUES   OF    THE   NERVOUS   SYSTEM. 

lated  fibres  which  are  distributed  to  the  bloodvessels  will  be 
described  elsewhere.) 

Nerves  of  the  Peritonaeum. — For  the  demonstration 
of  the  fine  fibres  of  the  peritonaeum  of  the  rabbit,  the  follow- 
ing is  the  best  method:  Three  drops  of  concentrated  acetic 
acid  are  added  to  twenty  cubic  centimetres  of  distilled  water. 
To  this  mixture  five  drops  of  half  per  cent,  solution  of  gold 
is  added.  The  fresh  peritonaeum  is  immersed  in  the  solution, 
and  allowed  to  remain  exposed  to  the  light  for  several  days 
until  it  becomes  darkly  stained.  Very  instructive  prepara- 
tions may  be  obtained  by  preparing  in  the  same  way  the  fold 
in  the  peritonaeum,  which  stretches  backward  and  to  the  left, 
from  the  diaphragm  to  the  upper  surface  of  the  stomach,  close 
to  the  cardia. 

Nerves  of  Unstriped  Muscular  Fibres. — The  bladder 
of  the  frog,  the  small  arteries  of  the  same  animal,  the  muscular 
coats  of  the  intestine,  or  of  the  vagina  of  the  rabbit,  may  be 
employed.  The  following  methods  are  applicable  :  As  regards 
the  bladder  of  the  frog,  the  previously  described  method  of  pre- 
paring the  muscular  fibres  themselves,  also  serves  for  the  de- 
monstration of  their  nerves.  In  the  bladder  of  mammalia,  the 
mixture  of  acetic  acid  and  gold,  mentioned  above  in  relation  to 
the  preparation  of  the  nerves  of  the  peritonaeum,  answers  well. 
After  the  preparation  is  sufficiently  stained,  thin  shreds  of 
muscular  tissue  are  stripped  from  the  external  surface  of  the 
swollen  membrane,  and  prepared  in  glycerin.  In  the  large 
arteries  of  the  mesentery  of  the  frog,  the  method  already  em- 
ployed for  the  demonstration  of  the  non-medullated  nerve 
fibres  of  the  mesentery  generally,  is  to  be  used.  The  relatively 
large  arteries  of  the  frog  (as,  e.  g.,  those  of  the  root  of  the  me- 
sentery) can,  as  a  rule,  lie  advantageously  prepared  by  placing 
them  for  five  minutes  in  half  or  one  per  cent,  acetic  acid,  and 
then  either  allowing  them  to  stand  in  the  gold  solution  twent}r 
to  thirty  minutes,  or  transferring  them  to  chromic  acid  solu- 
tion of  one-tenth  per  cent,  for  from  thirty  minutes  to  an  hour. 
For  the  unstriped  muscular  fibres  of  the  intestine,  uterus,  etc., 
sections  of  frozen  organs  may  be  treated  with  acetic  acid  and 
gold,  or  chromic  acid,  in  the  same  way.  Finally,  small  por- 
tions of  the  same  tissues  may  be  steeped  in  gold  solution, 
washed  in  distilled  water,  treated  with  tartaric  acid,  hardened 
in  alcohol,  and  employed  for  the  preparation  of  sections.  The 
facts  thus  demonstrated  maybe  summed  up  as  follows  :  Nerve 
trunks  of  various  size  run  in  the  sheaths  of  connective  tissue 
which  lie  between  the  muscular  bundles.  These  trunks  consist 
either  of  non-medullated  fibres,  or  of  medullated,  or  of  both 
kinds  mixed,  and  form  a  plexus  with  wide  meshes.  In  this 
(which  may  be  termed  the  principal  plexus)  the  ganglion  cells 
which  have  been  already  described  are  intercalated.     Its  nerves 


BY   DR.    KLEIN.  97 

give  off  numerous  fibres,  some  of  which  are  medullated,  but 
soon  lose  the  medullary  sheath,  others  non-medullated.  These 
last  are  pale,  streaked  longitudinally,  and  have  nucleated 
sheaths.  By  their  abundant  ramifications,  they  form  a  network 
of  rhomboidal  or  oblong  meshes,  having  nuclei  at  their  points 
of  junction.  This  network  involves  the  individual  muscular 
bundles,  and  is  called  the  intermediary  network.  Fine  fila- 
ments, containing  granules,  spring  from  it,  which  penetrate  be- 
tween the  muscular  cells,  and  divide  dichotomously  in  this 
situation,  forming  by  their  connection  the  intra-muscular  net- 
work. In  addition  to  the  fibrils  which  lie  between  the  fibres, 
the  network  contains  others,  which  penetrate  the  muscle-cells 
and  become  connected  with  the  nucleoli  of  their  nuclei,  in  such 
a  wajr,  however,  that  the  nucleolus  is  not  the  end  of  the  fibril, 
but  is  intercalated  in  it.  It  is  only  in  a  few,  out  of  a  great 
many  successful  preparations,  that  the  iutra-muscular  network 
can  be  demonstrated.  Most  serve  to  show  only  the  interme- 
diary plexus. 

Nerves  of  the  Striped  Muscles. — The  demonstration 
of  the  nerves  of  voluntary  muscle  has,  hitherto,  been  accom- 
plished only  in  fresh  preparations;  there  are,  however,  one  or 
two  cases  in  which  the  silver  method  can  be  used.  It  is,  in 
the  first  place,  to  be  borne  in  mind  that  only  muscles  that  are 
still  irritable  are  of  any  use  for  the  purpose.  Secondly,  that 
the  greatest  care  must  be  taken  in  making  the  preparation, 
especially  to  prevent  the  cover-glass  from  pressing,  by  strips 
of  paper. 

Muscular  Nerve  Endings  of  the  Water-beetle. — The 
muscles  of  certain  invertebrate  animals,  e.  g.,  Dytiscus,  or,  still 
better,  Hydrophilus  piceus,  and  particularly  those  which  pass 
from  the  thorax  to  the  legs,  are  best  suited  for  the  purpose. 
The. muscle  is  severed  near  its  insertion  with  fine,  sharp  scis- 
sors, and  at  once  placed  on  the  object-glass  and  covered,  or 
transferred  to  a  drop  of  serum  and  spread  out  so  as  to  sepa- 
rate a  few  muscular  fibres.  It  is  easy  to  recognize  the  broad, 
riband-shaped,  medullated  nerve  fibres,  each  possessing  a  stri- 
ated axis-cylinder,  which  rapidly  divide  into  finer  non-medul- 
lated fibres,  each  distinctly  streaked  and  beset  with  nuclei.  A 
single  muscular  fibre  may  receive  several  non-medullated  nerve 
fibres.  At  the  point  at  which  each  enters  the  muscular  sub- 
stance, a  more  or  less  marked  elevation  is  distinguishable,  the 
so-called  Doyere's  prominence.  This  consists  of  granular  sub- 
stance in  which  clear,  roundish  nuclei  are  embedded.  The 
prominence,  with  its  nuclei,  is  lengthened  out  into  processes  in 
directions  corresponding  with  that  of  the  axis  of  the  muscular 
fibre.  These  processes  may  either  stretch  along  the  surface  of 
the  muscular  fibre,  or  sink  into  its  depth.  Sometimes  the 
prominence  is  represented  by  a  mere  lamina  of  granular  sub- 
1 


98  TISSUES   OF   THE   NERVOUS   SYSTEM. 

stance,  which  does  not  project  above  the  surface.  The  axis- 
cylinder  penetrates  into  the  substance  of  the  prominence,  pass- 
ing through  the  sarcolemma,  with  which  its  Schwann's  sheath 
becomes  continuous.  It  usually  divides  dichotomously  in  the 
prominence,  each  branch  ending  in  a  rounded  extremity.  The 
prominence,  therefore,  consists  of  two  parts,  viz.,  the  axis- 
cylinder,  with  its  two  branches,  and  the  nucleated  granular 
substance  in  which  it  is  embedded.  The  granular  substance 
consists,  in  all  probability,  of  the  same  material  as  that  which 
constitutes  the  so-called  muscle-corpuscles. 

Muscular  Nerve  Endings  of  the  Frog. — In  many 
respects  the  nerves  of  the  muscles  of  the  frog  differ  from 
those  above  described.  In  the  first  place,  there  are  many 
muscular  fibres  which  are  entered  by  only  one  nerve.  In 
order  to  make  out  this  fact,  it  is  a  good  plan  to  place  portions 
of  muscle  in  a  mixture  of  chlorate  of  potash  and  nitric  acid 
at  40°  C. ;  or,  better,%to  place  the  tissue  for  twenty-four  hours 
or  more  in  diluted  sulphurous  acid,  after  which  it  is  exposed, 
still  remaining  in  the  liquid,  to  a  temperature  of  40°  for  a  few 
hours.  If  the  muscle  is  then  shaken  with  water  in  a  test  tube, 
the  individual  fibres  separate  very  readily  from  each  other,  and 
may  be  covered  without  further  preparation.  For  the  study  of 
the  finer  relation  of  the  muscular  nerves,  separate  fasciculi  of 
the  gastrocnemius  may  be  employed,  which  must  be  cut  out 
with  their  tendons — those  parts  being  chosen  to  which  vessels 
and  nerves  can  be  traced  with  the  naked  eye.  The  preparation 
is  covered  in  humor  aqueus,  after  it  has  been  spread  out  with 
great  care  with  needles.  It  is  then  possible  to  observe  that  a 
medullated  fibre  comes  into  contact  here  and  there  with  a 
muscular  fibre,  and  divides  into  several  medullated  branches. 
Just  as  the  branches  approach  the  point  at  which  they  enter 
the  sarcolemma,  in  order  to  attain  the  surface  of  the  muscular 
substance,  they  lose  their  medullary  sheath.  At  this  point, 
they  resolve  themselves  into  a  number  of  small  pale  filaments, 
which  run  parallel  to  the  long  axis  of  the  muscle,  keeping  close 
to  its  surface,  and  are  beset  with  oblong  structures  resembling 
nuclei.  Eventually,  each  terminates  abruptly  in  a  rounded 
end. 

Another  excellent  object  for  demonstration  of  the  muscular 
nerves  is  the  thoracic  cutaneous  muscle  of  the  frog,  which 
must  be  divided  along  its  insertions,  and  then  severed  from  its 
thoracic  attachments,  and  carefully  spread  out  in  a  drop  of 
humor  aqueus  and  covered,  care  being  taken  to  interpose  strips 
of  paper  underneath  the  edge  of  the  cover-glass.  It  is  also 
possible  to  demonstrate  the  nerve  endings  in  frog-muscles  with 
the  aid  of  nitrate  of  silver — the  same  parts  being  used  for  the 
purpose.  The  isolated  fasciculi  are  placed  in  serum,  to  which 
an  equal  quantity  of  distilled  water  has  been  added,  for  ten  or 


BY    DR.    KLEIN.  99 

fifteen  minutes.  Thence  they  are  transferred  to  a  quarter  per 
cent,  solution  of  nitrate  of  silver  for  thirty  or  sixty  seconds, 
and  then  exposed  to  the  light  until  they  acquire  a  brownish 
color.  They  are  further  prepared  in  a  drop  of  a  mixture  of 
equal  parts  of  ordinary  acetic  acid,  glycerine,  and  "water.  In 
such  preparations  a  s}'stem  of  clear  lines  shows  itself  in  the 
striped  brown  ground  of  muscular  substance.  These  lines 
correspond  exactly,  in  their  whole  arrangement,  with  the  intra- 
muscular nerves  above  described. 

Muscular  Nerve  Endings  of  Snakes  and  Lizards. — 
The  most  beautiful  muscular  nerve  endings  with  which  we  are 
acquainted  are  those  of  the  reptilia,  e.g.,  Lacerta  agilis,  Lacerta 
viridis,  and  Coluber  natrix.  In  preparations  of  the  muscle  of 
the  thigh  or  of  the  back  of  the  lizard  in  humor  aqueus  or 
serum,  it  is  seen  that  the  medullated  nerve  fibres  divide  into 
branches  in  the  same  way  as  in  the  frog.  Here,  as  before,  the 
branches  lose  their  medullary  sheath  just  as  they  enter  the 
sarcolemma,  and  then  resolve  themselves  into  a  beautiful  digi- 
tate or  fringe-like  expansion  of  pale  fibres  embedded  in  a 
granular  ground  containing  nuclei,  resembling  that  described 
in  Hydrojohilus,  but  of  a  laminar  form.  In  the  subcutaneous 
muscles  of  Coluber  natrix,  the  terminal  expansion  forms  a  rich 
network  of  riband-shaped  fibres  embedded  in  a  granular  ground. 
The  network  is  so  close  that  it  looks  like  a  lamina  in  which 
round  and  oval  orifices  have  been  punched  out.  In  silver 
preparations  made  as  above  directed,  as  well  in  the  lizard  as 
in  the  snake,  the  same  facts  may  be  demonstrated — the  intra- 
muscular system  of  nerves  exhibiting  themselves  as  clear  lines 
on  a  brown  ground. 

The  endings  of  the  muscular  nerves  of  mammals  resemble 
those  of  reptiles. 

From  the  preceding  details  it  appears  that  two  forms  of 
muscular  nerve  endings  may  be  distinguished.  In  the  first 
form,  the  ends  of  the  axis-cylinder,  or  those  of  its  branches, 
lie  in  immediate  contact  with  the  muscular  substance  under- 
neath the  sarcolemma  (frog).  In  the  second,  they  are  embed- 
ded in  a  granulous  ground  {Hydrophilus,  reptilia,  mammalia). 
The  demonstration  of  nerve  endings  is  one  of  the  most  difficult 
tasks  which  can  be  undertaken  by  the  histologist. 


100  METHODS. 


PART    II. 

PREPARATION  OF  THE  COMPOUND  TISSUES. 


CHAPTER  VI. 
METHODS. 

The  methods  of  examining  tissues  in  the  fresh  state,  with 
or  without  the  addition  of  reagents,  and  of  isolating  the  ele- 
ments by  the  process  of  teasing  with  needles,  have  been  fully 
described  in  the  First  Part.  We  have  also  seen  that,  in  trans- 
parent structures,  particularly  membranes,  the  anatomical 
relations  of  the  elements  may  be  studied,  either  by  observing 
them  in  the  natural  condition,  or  after  preparation  with  the 
solution  of  chloride  of  gold,  or  with  that  of  nitrate  of  silver. 
For  the  investigation  of  the  compact  tissues,  other  modes  of 
preparation  are  necessary,  in  order  to  bring  them  into  such  a 
condition  that  fine  sections  can  be  made  of  them.  It  is  the 
purpose  of  this  chapter  to  describe  the  method  by  which  this 
is  accomplished. 

Preparation  of  Sections  of  Fresh  Tissues. — There 
are  a  few  organs  or  parts  of  organs  which  possess  such  a  con- 
sistence that  it  is  possible,  without  preparation,  to  make  micro- 
scopical sections  of  them ;  such  as  cartilage,  some  tumors, 
skin,  hypertrophied  lymphatic  glands,  prostate  gland,  kidney, 
liver,  and  under  certain  circumstances  involuntary  muscle. 
Sections  of  these  tissues  serve  either  for  the  study  of  the  con- 
dition of  the  elements,  or  the  action  of  reagents  ;  or  are  made 
with  a  view  of  treating  them  with  gold  or  silver.  They  are, 
however,  mainly  useful  as  facilitating  the  preparation  of  the 
individual  elements  by  the  process  of  teasing.  For  this  pur- 
pose the  section  may  be  either  used  in  the  fresh  state  with 
indifferent  liquids,  or  after  maceration  in  iodized  serum,  Mid- 
ler's fluid,  or  one  per  cent,  solution  of  bichromate  of  potash. 

For  the  study  of  the  anatomical  relation  of  fresh  tissues, 
other  methods  must  be  used.  The  simplest  plan  is  to  take  the 
object  in  the  hand,  and  use  a  sharp  section  knife.  It  is  some- 
times recommended   to  fix  the  tissue  between  elder  pith  or 


BY   DR.    KLEIN.  101 

cork,  by  mechanical  means.  This  is  not  advantageous  on  the 
following  grounds  :  Those  tissues  which  are  soft  are  so  injured 
by  the  pressure  that  their  elements  are  in  a  completely  un- 
natural condition  ;  whereas,  in  the  case  of  firm  tissues,  it  is 
quite  easy  to  do  without  such  assistance. 

Preparation  of  Sections  by  Freezing. — For  the  pur- 
pose of  obtaining  sections  of  tissue  without  any  dislocation  or 
alteration  of  structure,  the  method  of  freezing  is  well  adapted. 
A  freezing  mixture  is  prepared  by  introducing  alternately 
small  quantities  of  broken  ice,  or  snow  (not  so  advantageous), 
and  of  finely  powdered  salt,  into  a  large  vessel,  mixing  the 
two  ingredients  thoroughly  after  each  addition.  The  tem- 
perature should  be  determined  by  the  introduction  of  a  ther- 
mometer. The  object,  which  must  be  small,  should  be  cut  to 
an  oblong  form,  and  placed  on  a  flat  cork,  much  wider  than 
itself.  It  must  be  pinned  to  this  cork  at  the  end  opposite  that 
from  which  the  sections  are  to  be  cut.  In  the  case  of  a  mem- 
brane, the  object  must  be  folded,  and  fixed  in  the  same  way. 
The  whole  is  then  placed  in  a  platinum  crucible,  which  has 
been  previously  plunged  into  the  freezing  mixture.  The  cru- 
cible must  be  at  once  covered,  and  a  little  of  the  freezing 
mixture  placed  on  the  top  of  it.  The  section  knife,  which 
must  be  sharp,  is  cooled  by  laying  it  on  ice.  As  soon  as  it  is 
ascertained,  by  exploration  with  a  needle,  that  the  preparation 
is  firm  enough,  the  knife  is  handed  to  an  assistant,  who  wipes 
it,  and  holds  it  in  readiness.  The  cork  is  then  taken  out  with 
the  forceps,  and  seized  by  the  fingers  of  the  left  hand  in  such 
a  way  that  they  do  not  come  into  contact  with  the  preparation. 
A  succession  of  sections  having  been  rapidly  made,  the  num- 
ber varying  with  the  skill  of  the  operator,  the  cork  is  replaced 
in  the  crucible.  The  sections  may  be  employed  either  for 
immediate  examination,  or  for  teasing,  or  subjected  to  further 
processes  of  preparation.  As  soon  as  the  portion  of  tissue  in 
the  crucible  is  again  of  the  proper  consistence,  more  sections 
can  be  made.  As  regards  the  temperature  which  should  be 
employed,  and  the  time  during  which  the  object  should  be 
frozen,  no  definite  rule  can  be  given.  It  may  be  stated,  in 
general,  that  temperatures  varying  from  — 6°  to  — 20°  C.  are 
sufficient  for  all  purposes.  The  time  necessary  for  the  attain- 
ment of  the  proper  degree  of  firmness  is  obviously  dependent 
on  the  temperature  of  the  freezing  mixture,  on  the  thickness 
of  the  object,  and  on  the  relative  quantity  of  water  it  contains. 
Accordingly  the  time  is  very  variable,  so  that  the  proper 
moment  for  removing  the  preparation  can  only  be  determined 
by  frequently  repeated  exploration  ;  by  which  means  alone  it 
i~  possible  to  avoid  the  risk  of  carrying  the  hardening  too 
far — a  result  which  is  alike  prejudicial  to  the  structure  of  the 
organ,  and  to  the  success  of  the  section. 


102  METIIODS. 

Methods  by  which  Tissues  are  Hardened  for  the 
Preparation  of  Sections. — For  the  purpose  of  rapidly 
hardening  tissues,  small  portions  may  be  advantageously 
placed  in  the  chloride  of  gold,  osmic  acid,  or  chloride  of  pal- 
ladium, and  kept  till  they  are  sufficiently  consistent.  Such 
preparations  must  usually  be  embedded  in  the  manner  to  be 
hereafter  described,  before  sections  are  made  from  them.  The 
sections  themselves  are  then  exposed  to  the  light  in  distilled 
water,  and  covered  in  glycerin.  Half  per  cent,  solution  of 
chloride  of  gold,  solutions  of  perosraic  acid  varying  from  one- 
tenth  to  two  per  cent.,  or  solutions  of  chloride  of  palladium 
from  one-tenth  to  half  per  cent.,  are  used. 

Other  agents  and  methods  in  use  are  the  following :  Alco- 
hol, oxalic  acid,  boiling  and  drying,  chromic  acid  and  its  com- 
pounds, (a)  For  thin  membranous  tissues,  hardening  in  alco- 
hol answers  well.  It  is  more  rapid  than  chromic  acid,  which, 
however,  has  superseded  it  for  many  purposes  for  which  it 
was  formerly  employed.  Absolute  alcohol  is  used  principally 
for  hardening  brain,  and  for  injected  tissues.  Common  alco- 
hol is  also  used  for  the  hardening  of  pancreas,  salivary  glands, 
and  the  glands  of  the  stomach  and  intestine,  and  of  objects 
which  have  been  already  treated  with  gold  or  silver.  Further, 
when  tissues  have  been  partly  hardened  in  chromic  acid  com- 
pounds, the  hardening  can  be  accelerated  and  completed  by 
subsequent  immersion  in  common  alcohol,  (b)  The  use  of 
oxalic  acid  and  oxalates,  and  other  similar  salts,  majr  be  en- 
tirely dispensed  with.  If  used,  weak  solutions  of  from  a  half 
to  two  per  cent,  are  preferable,  (c)  The  process  of  boiling, 
etc.,  is  entirely  relinquished.  In  former  times  it  was  employed 
for  intestine,  kidney,  trachea,  and  larynx.  The  intestine  was 
boiled  in  a  mixture  of  water,  creasote,  and  vinegar,  stretched 
on  cork,  and  dried.  Sections  were  made  with  scalpels,  and 
then  steeped  in  acetic  acid,  (d)  The  chromium  compounds 
are  the  most  valuable  agents  we  possess  for  hardening — viz., 
chromic  acid,  in  solutions  varying  in  strength  from  one-tenth 
to  half  per  cent.;  bichromate  of  potash,  in  solutions  from  half 
to  two  per  cent.,  and  MiilLr's  liquid,  which  consists  of  two 
parts  of  bichromate,  and  one  part  of  sulphate  of  soda,  in  100 
parts  of  water.  These  have  the  immense  advantage  that  they 
produce  no  marked  shrinking  or  distortion  of  the  tissues,  so 
that  they  retain  for  the  most  part  their  natural  characters. 
This  is  particularly  the  case  as  regards  bichromate  of  potash 
and  Midler's  liquid.  Very  small  portions  of  tissue  must  be 
used,  particularly  when  chromic  acid  is  employed,  for  it  pene- 
trates much  less  readily  into  the  tissues  than  the  others ;  so 
that  if  the  preparation  is  too  large,  it  is  apt  to  become  putrid 
in  the  centre,  while  the  outside  is  too  hard.  If  the  objects 
are  smeared  with  foreign  matters,  as,  e.  g.,  intestine  by  intes- 


BY   DR.   KLEIN.  103 

tinal  contents,  blood,  or  mucus,  it  is  desirable  to  rinse  them  in 
water  colored  \-ellow  b}*  bichromate  of  potash,  before  intro- 
ducing them  into  the  hardening  liquid.  The  quantity  of  liquid 
must  be  large  in  proportion  to  the  size  of  the  object.  If  the 
process  does  not  go  on  quickly  enough,  the  liquid  must  be  re- 
newed. Chromic  acid  hardens  much  more  rapidly  than  bi- 
chromate or  Midler's  liquid,  from  two  to  five  days  being  often 
enough  for  the  former,  while  as  many  weeks  are  required  for 
the  latter.  Its  greatest  disadvantage  is  that  the  tissue  be- 
comes brittle  if  it  is  left  in  it  beyond  the  time  that  is  neces- 
saiy.  It  is,  on  this  account,  a  good  plan  to  transfer  the 
objects  to  common  alcohol  before  they  have  acquired  the 
requisite  consistence.  The  alcohol  not  only  serves  to  com- 
plete the  hardening,  but  to  preserve  the  objects  in  a  state  fit 
for  use.  For  some  tissues,  chromic  acid  is  not  suitable  to 
begin  with,  e.  g.,  retina,  ovary,  or  kidnej^s.  For  all  these 
organs,  the  bichromate  of  potash  must  be  used.  After  two  or 
three  weeks  they  are  transferred  to  chromic  acid  or  alcohol,  to 
complete  the  hardening. 

Embedding. — It  has  been  several  times  mentioned  that 
small  portions  of  hardened  tissues  must  be  embedded.  This 
is  effected  by  immersing  the  bits  in  a  fluid  mass,  which  can  be 
rendered  solid  either  by  cooling  it  or  depriving  it  of  water; 
the  purpose  being,  first,  to  render  it  possible  to  hold  the  bit, 
and  secondly,  to  facilitate  the  cutting  of  sections  equally  thin 
throughout.  Mixtures  are  used  of  stearin  and  oil,  stearin  and 
wax,  paraffin  and  oil,  paraffin  and  wax,  paraffin  spermaceti 
and  oil,  wax  and  oil,  gum  arabic,  gelatin,  gelatin  and  glycerin. 
Among  the  fatty  mixtures,  the  best,  cheapest,  and  easiest  to 
prepare,  is  wax  and  oil.  Next  comes  the  mixture  of  paraffin 
spermaceti  and  oil.  For  portions  of  tissue  which  have  an  un- 
even surface,  especiall}'  if  the  inequalities  are  close  together, 
embedding  in  gelatin  or  gum  is  more  to  be  recommended, 
especially  to  those  who  have  not  had  much  practice. 

Embedding  in  Wax  and  Oil. — For  this  purpose  pure 
white  wax  and  pure  olive-oil  should  be  used.  Equal  quantities 
of  these  ingredients  are  warmed  in  a  capsule  till  all  the  wax  is 
fused;  they  are  then  thoroughly  mixed  with  a  glass  rod.  It 
is  better  to  prepare  a  considerable  quantity  at  a  time,  although 
only  very  little  is  required  for  one  embedding.  The  propor- 
tion of  wax  to  oil  depends  on  the  consistence  of  the  object  to 
be  embedded ;  the  more  wax  being  employed  the  firmer  the 
object,  and  vice  versa.  When  sections  of  compact  tissues  (e.  g., 
glands  of  the  organs  of  digestion,  trachea,  larynx  and  muscle, 
bone,  the  eye  and  its  appendages)  are  to  be  made,  the  mode  of 
procedure  is  as  follows:  If  the  organ  has  been  hardened  in 
alcohol,  an  oblong  bit  must  be  cut  from  it  with  a  razor,  in- 
cluding the  part  of  which  it  is  desired  to  make  sections.     If 


104  METHODS. 

it  has  been  hardened  in  any  aqueous  solution,  e.  g.,  chromic 
acid  or  bichromate  of  potash,  it  must  be  first  steeped  in  com- 
mon alcohol.  According  to  the  size  of  the  bit,  a  little  box  or 
case,  of  paper  or  any  suitable  material,  such,  for  example,  as 
zinc-foil,  must  be  made,  so  that  it  will  hold  the  fused  mixture. 
"When  paper  is  used,  the  sides  are  joined  with  gum  or  paste, 
or  are  merely  pinned  together.  The  box  should  be  about  half 
as  loiii;  again  as  the  object  used.  When  read}-,  it  is  filled  with 
the  fused  wax-mass  to  a  depth  sufficient  to  cover  the  object. 
As  soon  as  the  mass  begins  to  solidifj'  at  the  sides,  the  bit  is 
introduced  as  follows:  A  needle  is  stuck  slightly  into  the 
end  opposite  to  that  from  which  sections  are  to  be  cut,  and 
the  bit  is  plunged  into  the  mass  with  its  long  diameter  hori- 
zontal, and  in  such  a  position  that  the  end  furthest  from  the 
needle  is  near,  but  not  in  contact  with,  the  side  of  the  box, 
and,  consequently,  the  other  end  is  at  a  considerable  distance 
from  the  side.  In  this  way,  although  the  whole  is  surrounded 
with  the  wax  mass,  there  is  a  greater  thickness  around  the  end 
into  which  the  needle  is  stuck,  so  that  the  whole  can  be  se- 
curely and  conveniently  held.  The  solidification  can  be  accel- 
erated by  immersion  in  water  or  alcohol.  If  the  portions  of 
tissue  are  compact  enough,  it  is  possible  to  perforate  the  bit 
with  a  very  slender  needle,  the  point  of  which  is  stuck  into  the 
table  or  cork  on  which  the  box  rests;  by  this  means  the  ope- 
rator is  saved  the  trouble  of  holding  the  needle  till  the  wax- 
mixture  solidifies.  In  finally  withdrawing  the  needle,  the 
greatest  care  must  be  taken  to  give  it  a  twisting  motion,  as 
otherwise,  especially  if  the  object  is  thin,  it  is  apt  to  be  dis- 
placed. If  the  object  contains  a  cavity  communicating  with 
the  surface  by  a  single  opening  (e.  g.,  the  cochlea),  it  is  neces- 
sary first  to  fill  the  cavity  with  the  mass :  this  is  done  either 
by  placing  it  in  vacuo,  or  by  making  an  additional  opening. 
If  a  thin  membrane  is  to  be  embedded,  of  such  tenuity  that  a 
needle  could  not  be  introduced  without  danger  of  destroying 
it,  the  following  methods  may  be  used:  (1)  A  box  is  half 
filled  with  the  mass,  and  then,  as  soon  as  it  begins  to  solidify, 
the  membrane  is  applied  to  the  half-solid  surface,  in  such  a 
position  as  is  most  suitable  with  reference  to  the  direction  in 
which  the  section  is  to  be  made.  The  box  is  then  filled  with 
a  thoroughly  fused  mass,  care  being  taken  that  it  is  not  too 
hot.  (2)  The  fused  mass  is  allowed  to  drop  on  an  object-glass 
or  a  thin  flat  piece  of  cork,  so  as  to  form  a  layer  thick  enough 
to  serve  as  a  basis  for  the  object,  which  is  then  laid  upon  it 
and  covered  with  an  additional  layer  of  wax-mass.  If  an 
object-glass  is  used,  it  must  be  first  covered  with  turpentine, 
otherwise  it  will  be  difficult  to  remove  the  solidified  mass  from 
it.     In  all  cases  the  surface  of  the   object   must   be  nearly 


BY   DR.   KLEIN.  105 

dried  before  embedding,  otherwise  the  mass  will  not  adhere 
to  it. 

As  regards  the  other  fatty  masses,  the  only  one  which  can 
be  recommended  is  a  mixture  of  five  parts  paraffin,  two  parts 
spermaceti,  and  one  of  lard.  It  is,  however,  decidedly  inferior 
to  the  mass  of  wax  and  oil. 

Embedding  in  Gum  or  Gelatin. — It  has  already  been 
stated  that  objects  with  delicate  projections  in  close  proximity 
to  each  other  (e.  g.,  papillae  or  villi),  can  be  better  embedded 
in  gum  or  gelatin  than  in  wax  and  oil.  The  wax-mass,  in 
solidifying,  does  not  penetrate  between  the  projecting  parts, 
so  that  they  are  unsupported,  and  consequently  are  apt  to  be 
broken  off  in  making  sections.  Gum  is  solidified  by  immersion 
in  alcohol,  gelatin  by  cooling :  in  both  cases  the  process  is  so 
slow  that  the  mass  has  time  to  penetrate  between  the  inequali- 
ties of  the  surface  of  the  object.  The  gum  or  gelatin  solution 
must  be  concentrated  ;  to  the  gelatin  a  little  glycerin  should 
be  added.  I  think  gum  preferable,  first,  because  the  consist- 
ence of  the  solid  mass  can  be  varied  according  to  the  time  it 
is  left  in  alcohol ;  and  even  if  it  has  already  become  too  hard, 
it  ma}r  be  softened  b}'  adding  to  the  alcohol  a  few  drops  of 
water.  No  such  modification  is  possible  in  the  case  of  gelatin. 
It  is  also  more  easy  to  make  sections  in  gum  than  in  gelatin, 
the  elasticity  of  which  is  a  great  disadvantage.  On  the  other 
hand,  it  is  easier  to  embed  in  gelatin,  and  the  time  required  for 
solidification  is  much  shorter.  The  method  of  embedding  in 
gum  is  as  follows  :  A  thick  solution  of  powdered  and  sifted 
gum  arabic  is  prepared  in  a  beaker,  and  allowed  to  stand  in  a 
water-bath  until  all  air-bubbles  have  collected  at  the  surface  in 
the  scum,  which  must  then  be  removed  by  skimming  ;  after 
which  the  solution  may  be  used.  A  little  box  of  paper  is  then 
prepared,  of  suitable  size,  which  is  placed  on  a  plate  of  cork. 
The  bit  to  be  embedded  is  then  stuck  through  with  a  needle, 
the  point  of  which  is  thrust  into  the  cork  through  the  bottom 
of  the  box  ;  the  same  rules  being  followed  as  regards  the  posi- 
tion of  the  bit  in  the  box  as  in  embedding  in  wax-mass.  The 
whole  is  then  transferred  to  a  glass  capsule.  As  soon  as  the 
bit  is  nearly  dry  at  the  surface,  the  solution  is  poured  along  a 
glass  rod  into  the  box  until  it  is  full  to  the  brim.  Alcohol  is 
then  carefully  poured  into  the  capsule,  until  the  little  box  is 
immersed  to  half  its  height.  The  whole  must  then  be  covered 
over  and  left  for  two  or  more  hours.  As  soon  as  the  gum  be- 
comes opaque  and  white  on  the  surface,  which  occurs  in  about 
the  time  mentioned,  the  whole  mass  can  be  immersed  in  alco- 
hol until  it  is  brought  to  the  required  degree  of  solidity.  The 
process  may  be  accelerated  either  by  changing  the  alcohol 
frequently,  or  by  using  absolute  alcohol.  If  the  mass  is  too 
hard,  it  can  be  softened  by  adding  a  drop  or  two  of  water  to 


10G  METHODS. 

the  alcohol,  as  has  been  already  stated.  When  gelatin  is  used, 
the  mode  of  procedure,  so  far  as  relates  to  the  preparation  of 
the  solution,  is  similar.  The  bit  having  been  fixed  into  the 
box  and  surrounded  with  the  solution,  the  whole  is  allowed  to 
stand  until  it  becomes  solid.  Whichever  material  is  used,  the 
mass  is  freed  from  the  paper  box  as  soon  as  it  has  acquired 
sufficient  firmness,  and  the  ends  of  the  needle  are  snipped  off 
above  and  below. 

Preparation  of  Sections  of  Hardened  Tissues. — For 
making  sections,  razors  are  most  used.  Other  instruments 
are  also  employed,  the  purpose  of  which  is  to  make  up  for 
want  of  skill  in  the  operator.  The  principal  ones  are  Valentin's 
knife,  the  microtome  of  Hensen,  that  of  His,  another  micro- 
tome lately  described  by  Brandt,  and  the  section  cutter  of 
Stirling,  lately  improved  by  Rutherford.  Of  these,  the  most 
useful  is  that  of  His,  which  has  the  advantage  that  it  is  possi- 
ble to  cut  with  it  successive  sections  of  an  organ  in  equidistant 
planes,  parallel  to  each  other,  with  the  greatest  exactitude. 

The  razor  or  section  knife,  in  the  hands  of  a  skilful  operator, 
is  superior  to  any  of  these  contrivances.  The  knife  I  use  is  of 
the  form  shown  in  Fig.  1 G.  The  blade  measures  eight  inches  ; 
the  wooden  handle  is  massive,  so  that  it  can  be  firmly  grasped. 
One  side  of  it  is  flat,  the  others  slightly  concave,  it  is  thus  ex- 
tremely thin  to  a  considerable  distance  from  the  cutting  edge. 
When  sections  are  to  be  made  of  objects  embedded  in  wax- 
mass,  the  knife  must  be  wetted  with  common  alcohol,  in  which 
liquid  each  section  must  be  immersed  as  soon  as  it  is  made. 
Sections  of  objects  which  have  been  embedded  in  gum  or  gela- 
tin must  be  placed  in  water,  but  the  knife  wetted  with  alcohol. 

Coloring  of  the  Sections. — It  is  quite  unnecessary  to 
refer  to  all  the  colored  liquids  which  have  been  used  for  stain- 
ing. It  will  be  sufficient  to  describe  the  mode  of  using  carmine 
and  anil  in. 

Carmine. — The  most  simple  solution  for  the  purpose  is  the 
following:  Two  grammes  of  carmine  in  fine  powder  are  tho- 
roughly mixed  in  a  beaker,  with  a  few  drops  of  water.  Four 
cubic  centimetres  of  liquor  ammonhe  are  then  added,  and  forty- 
eight  cubic  centimetres  of  distilled  water.  The  liquid  is  filtered 
into  the  stoppered  bottle,  in  which  it  is  to  be  kept.  The  bottle 
is  then  left  open  for  a  few  days,  in  order  to  get  rid  of  the  excess 
of  ammonia.  One  or  two  drops  of  this  solution  are  introduced 
into  a  watch-glass,  and  diluted  with  distilled  water  to  such  an 
extent,  that  when  it  is  placed  on  a  written  or  printed  sheet  of 
paper,  the  letters  can  onl}rjust  be  distinguished  through  it. 
The  sections  are  immersed  in  the  diluted  liquid  till,  on  inspec- 
tion, they  appear  to  have  the  tint  desired.  Prolonged  steeping 
in  dilute  solution  gives,  as  a  rule,  better  results  than  rapid 
straining  in  strong  solution;  for,  in  the  former  case,  although 


BY    DR.   KLEIN.  107 

the  color  is  less  intense,  the  different  tissues  are  rendered  dis- 
tinct by  the  different  degrees  to  which  they  are  stained.  I  use 
the  carmine  solution  for  this  purpose  as  follows:  The  sections, 
having  been  allowed  to  remain  for  twenty  or  twenty-four  hours 
in  a  liquid  consisting  of  one  part  of  carmine  solution  and  nine 
to  twelve  parts  of  distilled  water,  are  washed  for  a  short  time 
in  distilled  water,  and  transferred  either  to  glycerin  (if  it  is  in- 
tended to  mount  them  in  this  medium),  or  to  alcohol  (if  they 
are  to  be  mounted  in  Dammar).  If  the  sections  have  not  been 
previously  in  alcohol,  it  promotes  the  staining  to  put  them  for 
a  few  minutes  into  that  liquid.  If  it  is  intended  to  preserve 
the  sections  in  gtycerin,  it  is  desirable  to  add  a  few  drops  of  it 
to  the  staining  liquid.  The  well-known  liquid  used  by  Beale 
for  staining  fresh  tissues  may  be  also  employed  for  staining 
sections;  but,  in  preparing  it  for  this  purpose,  the  alcohol  may 
be  omitted.     The  composition  of  Beale's  liquid  is  as  follows: — 

Beale's  Solution. — Ten  grains  of  carmine  are  heated  in 
half  a  drachm  of  liquor  ammonia?.  As  soon  as  the  liquid  is 
cold,  two  ounces  of  distilled  water,  two  ounces  of  pure  glycerin, 
and  half  an  ounce  of  alcohol  are  added.  The  solution  is  then 
either  filtered  or  decanted  from  the  undissolved  carmine.  This 
liquid  requires  no  dilution.  A  small  quantity  must  be  warmed 
in  a  watch-glass  to  get  rid  of  the  ammonia,  and  it  is  then  ready 
for  use.  We  shall  find  that,  in  the  preparation  of  the  mucous 
membrane  of  the  stomach,  it  is  of  special  value. 

Anilin — Anilin  is  used  in  aqueous  and  alcoholic  solution  ; 
the  former  being  most  useful.  It  is  obtained  by  treating  anilin 
blue  with  sulphuric  acid.  Two  centigrammes  of  the  soluble 
product  are  dissolved  in  twenty-five  centimetres  of  distilled 
water,  and  twenty  to  twenty-five  drops  of  alcohol.  This  solu- 
tion colors  sections  which  have  been  in  alcohol  very  rapidly. 

Picric  Acid  is  used  in  very  dilute  solution  for  the  purpose 
of  staining  sections  yellow.  Sections  may  be  first  stained  in 
picric  acid,  then  in  carmine,  in  which  case  the  muscles  are  col- 
ored yellow.  Whatever  the  staining  liquid  employed,  the  sec- 
tions must  be  transferred,  as  soon  as  they  are  sufficiently  col- 
ored, to  distilled  water  with  or  without  the  addition  of  a  trace 
of  acid. 

Methods  of  Mounting  Sections. — Sections  maybe  cov- 
ered either  in  glycerin,  in  mixtures  of  gelatin  and  glycerin,  of 
glycerin  and  acetic  acid,  of  glycerin  acetic  acid  and  alcohol,  in 
Canada  balsam,  or  in  Dammar  varnish.  If  glycerin  is  to  be 
used,  the  sections  should,  if  they  have  been  in  alcohol,  be  pre- 
viously placed  in  water.  Glycerin  alone,  answers  best  for  sec- 
tions of  tissues  treated  with  gold  or  silver.  Sections  of  organs 
treated  with  osmic  acid  must  be  placed  in  acetate  of  potash. 
Very  thin  unstained  sections  of  glandular  organs  and  of  con- 


108  METHODS. 

nectivc  tissue  ma}-  be  temporarily  mounted  in  glycerin,  but 
cannot  be  preserved  for  a  length  of  time  in  that  liquid. 

All  sections  which  are  intended  to  be  permanent,  excepting 
those  of  tissues  prepared  by  the  gold  or  silver  methods,  must 
be  mounted  in  Canada  balsam  or  Dammar ;  the  last  being 
preferable,  as  more  easy  to  manipulate.  It  is  prepared  as 
follows: — 

Preparation  of  Dammar  Varnish. — Half  an  ounce  of 
gum  Dammar  in  powder,  is  dissolved  in  an  ounce  and  a  half 
or  two  ounces  of  turpentine,  and  half  an  ounce  of  gum  mastic 
in  two  ounces  of  chloroform.  The  two  solutions  are  then 
separately  filtered  and  mixed.  This  varnish  so  obtained  is 
clear,  and  if  exposed  in  a  thin  layer  on  a  plate  of  glass  solidi- 
fies rapidly.  The  sections  which  are  to  be  mounted  must  be 
placed,  for  a  quarter  of  an  hour  or  more,  in  a  capsule  contain- 
ing absolute  alcohol,  which  should  be  provided  with  a  cover. 
Each  section  must  be  raised  with  the  aid  of  a  german-silver 
or  copper  lifter  (the  blade  of  which  is  then  placed  on  blotting- 
paper,  to  remove  the  adhering  alcohol),  and  transferred  to  a 
watch-glass  containing  oil  of  cloves.  B}r  this  means  it  be- 
comes, in  a  few  seconds,  quite  transparent.  If  it  is  colored, 
the  color  becomes  more  intense;  if  it  is  unstained,  it  becomes 
almost  invisible.  From  the  oil  of  cloves  it  is  transferred  by 
the  same  means  to  a  drop  of  Dammar  varnish,  previously 
placed  in  the  centre  of  an  object-glass.1 

If  excessively  delicate  and  thin  sections  are  to  be  mounted, 
such,  e.  g.,  as  sections  of  the  retina,  or  of  any  thin  membrane, 
it  is  not  possible,  without  risk,  to  transfer  them  from  one 
liquid  to  another.  In  this  case  it  is,  therefore,  necessary  to 
swim  the  section  directly  from  the  knife  on  to  the  object-glass, 
in  which  position  they  must  be  treated  with  the  several  liquids 
to  be  employed  ;  and  each  liquid  must  be  allowed  to  fall  on 
to  the  section,  and,  after  producing  its  effect,  removed  by  in- 
clining the  glass,  care  being  taken  not  to  allow  the  object  to 
float  away  at  the  same  time.  All  delicate  sections  must  be 
protected  by  the  interposition,  between  the  object  and  cover- 
glass,  of  a  square  of  silver  paper,  with  a  window  cut  in  it 
somewhat  smaller  than  the  latter. 

Methods  of  Preserving  Preparations  permanently. 
— Preparations  which  are  to  be  preserved  must  be  mounted 

1  The  lifter  or  spoon  may  be  made  by  flattening  the  end  of  a  copper 
or  german-silver  wire,  and  bending  it  at  right  angles.  It  is  desirable 
to  place  the  object-glass  on  a  white  ground  if  the  object  is  stained,  or 
on  a  black  ground  if  it  is  unstained,  in  order  that  the  folds,  if  present, 
may  be  seen  and  removed.  If  several  sections  are  to  be  placed  under 
one  cover-glass,  each  section  may  be  pressed  gently  down  on  the  sur- 
face of  the  glass  before  covering  ;  the  sections  then  adhere  to  the  glass 
sufficiently  to  keep  in  their  places. 

f 


BY   DR.    KLEIN.  109 

permanently.  Those  which  are  in  liquids,  such  as  glycerin, 
acetate  of  potash,  bichromate  of  potash,  etc.,  must  be  sur- 
rounded with  cement,  in  order  to  fix  the  cover-glass.  For 
those  which  are  in  glycerin  jelly,  Canada  balsam  (neither  of 
which,  however,  are  to  be  recommended),  or  Dammar  varnish, 
that  is  not  neeessaiy.  Various  kinds  of  varnish  are  used  for  the 
purpose,  such  as  Frankfort  lac,  asphalt,  etc.  I  use  always 
Dammar  varnish.  A  streak  of  the  varnish  is  placed  on  the  edge 
of  the  cover-glass  and  carried  all  round  it,  with  the  aid  of  a 
glass  rod  drawn  to  a  point,  or  a  brush,  care  being  taken  that  it 
extends  only  a  very  little  over  the  cover-glass.  Before  apply- 
ing the  varnish,  the  excess  of  liquid  must  be  carefully  removed 
with  blotting-paper  from  the  edge  of  the  cover-glass.  I  dis- 
pense with  the  instrument  frequently  used  for  mounting,  for  the 
following  reasons  :  If  the  cover-glass  is  already  fixed,  as,  e.  g., 
in  Canada  balsam  or  Dammar  preparations,  any  additional 
mounting  is  unnecessary.  If  it  is  not  fixed,  i.  e.,  when  the 
medium  in  which  the  preparation  is  contained  is  liquid,  there 
is  much  greater  risk  of  displacement  with  the  machine  than 
without  it.  It  should  always  be  borne  in  mind  that  the  pre- 
servation of  the  preparation  is  of  more  importance  than  the 
outside  setting.  The  other  kinds  of  varnish  may  be  used  in- 
stead of  labels,  for  writing  on  the  glass  the  name  of  the  pre- 
paration. If  it  is  desired  to  preserve  a  preparation  already 
covered  in  water  and  solution  of  osmic  acid,  or  bichronmte  of 
potash,  etc.,  without  removing  the  cover,  so  as  to  avoid  risk 
of  displacement,  the  best  way  is  to  irrigate  it  with  glycerin  or 
acetate  of  potash,  until  the  one  liquid  is  replaced  by  the  other. 
The  excess  of  liquid  must  then  be  removed  with  blotting- 
paper,  and  the  cover-glass  surrounded  with  Dammar  varnish. 
If,  l>3'  inadvertence,  the  upper  surface  of  that  part  of  the  cover- 
glass  which  is  above  the  preparation  has  been  smeared  with 
glycerin  or  Dammar  varnish,  and  it  is  desired  not  to  remount 
it,  the  only  way  is  to  wait  until  the  setting  is  dry.  The  spot 
can  then  be  removed  with  a  camel-hair  pencil  soaked  in  water 
if  it  be  glycerin,  or  in  turpentine  and  afterwards  in  alcohol  if 
it  be  Dammar. 


110  VASCULAR   SYSTEM. 


CHAPTER  VII. 
VASCULAR  SYSTEM. 
Section  I. — Methods  of  Injection.    » 

Before  describing  the  structure  of  the  bloodvessels  and 
lymphatics,  an  account  will  be  given  of  the  methods  of  inject- 
ing. The  processes  of  injection  may  be  divided  according  as 
they  are  used  during  life  or  after  death. 

Methods  of  Injecting  during  Life. — The  method  of 
injecting  the  vessels  of  an  animal  during  life  has,  hitherto,  not 
been  much  employed.  It  may  be  practised  either  for  the  pur- 
pose merely  of  introducing  into  the  circulation  any  suitable 
liquid  containing  coloring  matters,  or  other  substances  in 
solution  or  suspension,  or  with  a  view  to  empt3*ing  the  vessels 
of  their  contents  and  substituting  another  liquid.  For  ex- 
ample, we  have  already  seen  that  insoluble  coloring  matters 
are  introduced  in  order  to  feed  the  colorless  blood  corpuscles 
and  those  of  the  connective  tissue  ;  and  we  shall  subsequently 
see  that  hy  the  injection  of  colored  solutions,  a  "natural 
injection,"  produced  by  excretion  of  the  ducts  of  certain 
glandular  organs,  may  be  obtained.  (See  Chapter  X.)  The 
most  important  insoluble  coloring  matters  are  vermilion,  car- 
mine, and  anilin,  which  are  used  suspended  in  salt  solution,  as 
described  in  Chapter  I.  p.  26.  Insoluble  Prussian  blue,  as 
precipitated  by  the  gradual  addition  of  alcohol  to  the  solution, 
can  also  be  used  in  the  same  way. 

The  methods  are  as  follow  : — 

Injection  of  the  Frog  during  Life. — In  a  large  frog, 
secured  on  its  back,  the  abdominal  vein  is  carefully  exposed 
under  a  dissecting  lens,  in  its  course  up  the  middle  line  of  the 
anterior  wall  of  the  bell}'.  A  ligature  is  passed  round  the 
distal  end  of  the  prepared  part  and  tightened.  A  small  clip 
is  then  placed  on  the  proximal  end,  and  a  ligature  passed 
under  the  vein  between  the  two,  which  is  looped,  but  not 
tightened.  The  vein  having  then  been  opened  just  beyond  the 
loop,  with  a  pair  of  sharp  scissors,  a  fine  glass  canula  is 
introduced  in  the  direction  of  the  circulation.  The  loop  is 
then  tightened  round  the  canula  and  knotted.  The  canula 
must  now  be  filled,  with  the  aid  of  a  capillary  pipette,  with 
salt  solution,  and  connected  by  a  bit  of  india-rubber  tubing 
with  a  brass  syringe,  in  doing  which  great  care  must  be  taken 


BY    DR.    KLEIN.  Ill 

not  to  tear  the  canula  out  of  the  vein.  If  it  is  desired  to 
continue  the  injection  for  some  time,  it  is  better  to  employ  the 
pressure  of  a  column  of  liquid,  for  which  purpose  the  following 
arrangement  must  be  used:  A  moderate-sized  flask,  contain- 
ing the  injection  liquid,  is  supported  on  a  retort-holder  at  a 
height  of  about  two  or  three  feet  above  the  table.  The  flask* 
is  fitted  with  a  cork,  in  which  two  tubes  are  fixed,  the  one 
being  straight  for  the  admission  of  air,  the  other  bent  so  as  to 
form  a  syphon,  the  short  leg  of  which  dips  under  the  level  of 
the  liquid.  To  the  other  end  an  india-rubber  tube,  furnished 
with  a  screw-clamp,  is  fitted,  long  enough  to  reach  the  canula. 
A  current  is  now  produced  along  the  tube  by  suction,  which 
can  be  regulated  b}'  the  clamp  so  as  to  allow  the  liquid  to  flow 
in  a  rapid  succession  of  drops.  The  tube  is  then  momentarily 
closed  b3r  a  second  clip,  and  connected  with  the  canula.  The 
clip  on  the  tube  is  now  opened  and  that  on  the  vein  removed. 
As  soon  as  the  injection  is  finished  the  vein  is  ligatured  on  the 
proximal  side  of  the  canula,  which  is  then  withdrawn.  In 
long  injections,  it  is  of  course  necessary  to  open  the  peripheral 
end  of  the  vein.  If  it  is  desired  tq,  estimate  the  quantity  of 
liquid  injected,  a  cylindrical  bottle  is  substituted  for  the  flask, 
which  must  be  previously  graduated.  When  the  object  in  view 
is  to  replace  the  blood  completely  with  salt  solution  (with  or 
without  coloring  matter),  it  is  better  to  introduce  the  canula 
into  the  bulbus  arteriosus. 

Injection  of  small  Mammalian  Animals  during  life. 
— The  animal  is  secured  with  the  aid  of  Czermak's  holder. 
(See  Chapter  XYI.)  The  external  jugular  is  then  exposed 
by  a  sufficient  incision,  and  cleared  of  the  sorrounding  tissue 
with  the  aid  of  dissecting  forceps.  The  vessel  having  been 
ligatured  at  the  distal  end  of  the  prepared  part,  and  a  clip 
placed  on  it  at  the  central  end,  the  vein  is  opened  by  a  small 
incision,  and  a  proper  canula  inserted  and  secured  with  a 
ligature.  The  canula  is  then  filled  with  salt  solution  with  the 
aid  of  a  capillary  pipette,  and  connected  either  with  the 
syringe  or  the  tube  of  the  syphon  previously  described. 
Finally,  the  clip  is  opened,  and  the  liquid  allowed  gradually 
to  enter  the  vein.  As  soon  as  the  injection  is  completed,  the 
clip  is  immediately  closed.  Before  the  canula  is  removed,  the 
vein  is  of  course  ligatured.  If  the  quantit}r  to  be  injected  is 
small,  it  is  simpler  to  use  a  small  subcutaneous  syringe,  in 
which  case  all  that  is  necessary  is  to  compress  the  vein  imme- 
diately above  the  clavicle,  and  to  pierce  it,  when  distended, 
with  the  point  of  the  canula.  The  pressure  having  been 
discontinued,  the  liquid  is  at  once  injected.  The  aperture 
must  be  seized  by  means  of  clip-forceps  as  the  canula  is  with- 
drawn, so  as  to  prevent  bleeding. 


112  VASCULAR   SYSTEM. 

Injection  after  Death. — The  materials  used  for  this  pur- 
pose are  Prussian  blue,  carmine,  and  nitrate  of  silver. 

Prussian  blue,  like  carmine,  can  be  injected  either  in  solu- 
tion or  suspension  in  water,  or  in  solution  in  gelatin.  Silver 
is  mostly  used  in  solution  in  water.  Soluble  Prussian  blue, 
which  is  more  used  for  injection  than  any  other  coloring 
matter,  is  prepared  according  to  the  method  of  Briicke.  217 
grammes  of  ferro-cyanide  of  potassium  are  dissolved  in  a  litre 
of  water  iu  a  large  flask  (Solution  A).  In  another  flask  a 
solution  (B)  of  chloride  of  iron  is  prepared,  containing  one 
part  of  the  salt  in  ten  parts  of  water.  A  third  solution  (C)  is 
prepared  of  sulphate  of  soda,  which  must  be  saturated.  Equal 
parts  of  the  solutions  A  and  B  are  mixed,  each  with  twice  its 
bulk  of  C.  The  chloride  of  iron  mixture  is  then  poured  slowly 
into  the  mixture  containing  the  yellow  prussiate,  care  being 
taken  to  stir  constantly  during  the  addition.  The  precipitate 
having  been  allowed  to  settle,  the  greenish  supernatant  liquid 
is  poured  away,  and  the  residue  thrown  into  a  flannel  strainer. 
The  blue  liquid  which  passes  through  is  returned  to  the 
strainer  until  it  become^  transparent.  Thereupon  what  re- 
mains on  the  filter  is  washed  with  water  until  what  passes 
through  is  of  an  intense  blue  color.  The  filter  is  allowed  to 
drain  completely,  and  then  placed  between  shreds  of  blotting 
paper,  and  left  to  dry  gradually  in  a  sufficiently  cool  place.  It 
is  then  broken  up  into  small  fragments  and  kept  in  a  glass 
bottle.  The  blue  material  so  prepared  is  perfectly  and  readily 
soluble  in  water. 

A  two  per  cent,  solution  of  this  material  may  be  used  either 
at  the  ordinary  temperature  or  at  the  temperature  of  the  bod\r. 
It  can  be  injected  with  great  facility.  When  it  is  used  with 
gelatin,  the  mass  is  prepared  by  adding  five  parts  of  the  fil- 
tered solution  above  mentioned  to  one  hundred  parts  of  solu- 
tion of  gelatin,  containing  one  part  of  gelatin  to  eight  of 
water.  The  gelatin  is  first  dissolved  in  the  water  over  a  water- 
bath  in  a  porcelain  dish  ;  the  hot  solution  is  then  filtered 
through  flannel  or  fine  calico,  it  is  replaced  on  the  water-bath, 
and  the  blue  liquid  is  gradually  added  to  it  with  constant 
agitation. 

[There  are  some  other  blue  liquids  of  the  same  kind  in  use : 
"Beetle's  Prussian  blue  fluid"  is  prepared  as  follows :  Take 
one  ounce  of  common  glycerin,  one  ounce  of  spirits  of  wine, 
twelve  grains  of  ferro-cyanide  of  potassium,  one  drachm  of 
tincture  or  solution  of  perchloride  of  iron,  and  four  ounces  of 
water.  The  ferro-cyanide  is  dissolved  in  half  an  ounce  each 
of  water  and  glycerin,  and  the  iron  mixed  with  similar  quanti- 
ties of  both  ingredients.  The  chloride  of  iron  mixture  is 
thereupon  added  gradually  to  the  ferro-cyanide,  with  constant 
agitation.     Finally,  the  spirits  of  wine,  and  the  remainder  of 


BY    DR.    KLEIN.  113 

the  water  are  added  gradually.  "  TurnbulV 's  Blue." — Ten 
grains  of  protosulphate  of  iron  are  dissolved  in  an  ounce  of 
glycerin  diluted  with  a  little  water.  Thirty-two  grains  of  ferro- 
cyanide  of  potassium  are  dissolved  in  the  same  quantity.  The 
iron  is  then  added  to  the  red  prussiate  with  constant  agitation. 
Beale  modifies  this  formula  by  substituting  five  grains  of  sul- 
phate of  iron  and  ten  of  the  red  prussiate  for  the  quantities 
above  stated,  and  adding  to  the  mixture  an  ounce  of  water 
and  a  drachm  of  alcohol.] 

Carmine. — A  mass  which  is  fluid  at  ordinary  temperature 
is  prepared,  according  to  Beale,  as  follows  :  Take  five  grains 
of  carmine,  half  an  ounce  of  glycerin  containing  eight  or  ten 
drops  of  acetic  acid,  one  ounce  of  pure  glycerin,  two  drachms 
of  alcohol  and  §ix  drachms  of  water.  The  carmine  is  first 
mixed  with  a  little  water  containing  about  five  drops  of  ammo- 
nia. Half  an  ounce  of  pure  glj'cerin  having  been  added  to 
this  liquid,  it  is  shaken  in  a  flask,  and  then  gradually  poured 
into  the  acidulated  glycerin,  with  constant  .agitation.  If  the 
mixture  is  not  distinctly  acid,  a  trace  of  acetic  acid  is  added  to 
the  remaining  half  ounce  of  glycerin,  which  with  the  alcohol 
and  water  is  then  gradually  added  to  the  rest.  It  is  necessary 
to  prepare  this  mixture  each  time  that  it  is  used.  The  alcohol 
may  be  omitted  altogether  without  detriment.  Carmine  is 
usuall}-  emplo}'ed  in  solution  of  gelatin.  The  following  liquids 
are  to  be  recommended  : — 

Ge7-lach,is  Carmine  Mass. — Sixty-nine  grains  of  carmine  are 
dissolved  in  seventy  grains  of  water  with  eight  drops  of  liquor 
ammoniae.  The  solution,  having  been  exposed  to  the  air  for 
several  days,  is  mixed  with  a  solution  of  one  and  a  half  drachm 
of  gelatin  in  one  and  three-quarter  drachm  of  water.  A  few 
drops  of  acetic  acid  are  added  to  the  warm  mixture.  Dr.  Car- 
ter's Carmine  3fass. — Take  sixty  grains  of  carmine,  120 
grains  of  liquor  ammonias,  eighty-six  minims  of  glaciai  acetic 
acid,  two  ounces  of  solution  of  gelatin,  containing  one  part 
in  six,  one  and  a  half  ounce  of  water.  The  carmine  is  dis- 
solved in  the  ammonia  and  water  and  filtered.  The  filtrate  is 
added  to  one  and  a  half  ounce  of  solution  of  gelatin.  The 
other  half  ounce  is  mixed  with  the  acetic  acid,  and  added  gut- 
tali in  to  the  rest,  with  constant  agitation. 

I  found  this  mass  answer  extremely  well  with  the  following 
modification:  Four  grammes  of  carmine  having  been  sus- 
pended in  a  few  drops  of  water,  eight  cubic  centimetres  of 
liquor  ammonia?  and  forty-eight  cubic  centimetres  of  water  are 
added.  As  soon  as  the  carmine  is  dissolved,  the  liquid  is  fil- 
tered— a  process  which  requires  several  hours.  A  gelatin  so- 
lution, containing  one  part  in  eight  of  gelatin,  is  next  prei)ared 
and  filtered  through  fine  calico.  The  carmine  solution  is  added 
gradually  to  two  ounces  of  the  filtrate,  which  is  kept  warm 
8 


114  VASCULAR    SYSTEM. 

over  the  water-bath.  Forty  or  fifty  minims  of  glacial  acetic 
acid  are  then  added  to  another  half  ounce  of  warm  gelatin  solu- 
tion, which  is  mixed  gradually  with  the  rest,  with  constant 
agitation.  Before  the  whole  of  the  acid  gelatin  is  added,  the 
mixture  changes  its  color  from  bright  red  to  dirty  red.  I>y 
the  addition  of  the  last  drops,  the  mass  acquires  the  slight 
acid  reaction  which  is  necessary  to  render  it  indiffusible  in  the 
tissues. 

Silver  Solution. — The  solution  of  silver  used  for  injection 
contains  one-quarter  or  half  per  cent,  of  the  salt. 

Apparatus  and  Instruments. — Syringes  of  the  ordi- 
nary form  answer  well.  They  may  be  made  of  brass  or 
German  silver.  They  are,  however,  now  used  only  for  special 
purposes,  e.  g.,  for  the  injection  of  very  small  organs,  and  are 
open  to  the  objection  that  much  practice  is  required  in  order 
to  regulate  the  pressure  in  such  a  way  as  to  insure  success; 
deficient  pressure  rendering  the  injection  imperfect,  too  much 
producing  extravasation.  In  general,  and  indeed  in  all  cases 
in  which  it  is  desirable  that  the  pressure  should  be  constant 
throughout,  the  apparatus  to  be  hereafter  described  must  be 
used.  Canulas. —  When  the  syringe  is  used,  it  is  better  to 
employ  metal  canulas  than  glass  ones.  The  former  consist  of 
three  parts  (Fig.  17),  viz.,  a  collar,  with  two  cross  arms,  and 
a  tubular  beak.  The  beak  is  bevelled  at  the  end,  and  is 
grooved  at  a  short  distance  from  the  bevelling.  The  dimen- 
sions of  the  whole  are  accurately  shown  in  the  drawing.  The 
point  must  be  carefully  rounded.  The  nozzle  of  the  syringe 
is  plugged  into  the  collar,  and  is  fitted  with  a  stopcock,  in 
order  to  prevent  the  mass  from  returning  after  the  injection  is 
completed.  This  object  can  also  be  answered  by  a  ligature, 
but  in  many  cases  this  would  be  difficult  from  want  of  space. 
Three  or  four  such  canulas  with  beaks  of  different  calibres  are 
necessary.  Glass  canulas  should  be  made  of  the  following 
form  :  A  tube  is  drawn  out  in  such  a  manner  that  it  tapers  to 
a  degree  which  varies  according  to  the  size  of  the  vessel  into 
which  it  is  intended  to  be  introduced.  The  end  must  be  trun- 
cated and  smooth,  and  must  have  a  constriction  at  a  distance 
of  about  three  millimetres.  The  large  end  should  also  be  a 
little  drawn  out,  so  that  an  India-rubber  tube  can  be  easily 
slipped  over  it,  and  secured. 

The  various  forms  of  apparatus  for  injection  all  depend  on 
the  principle  that  the  pressure  which  is  required  for  injecting 
is  produced  by  the  influx  of  water  or  mercury  into  a  closed 
vessel.  The  mechanical  arrangements  employed  for  this  pur- 
pose are  as  follow :  A  bottle  containing  water  is  suspended  by 
a  pulley,  so  that  it  can  be  raised  to  any  required  height. 
From  a  tubulature  near  the  bottom  a  flexible  tube  issues, 
which  reaches  to  the  table,  and  is  connected  with  a  glass  tube, 


BY    DR.    KLEIN.  115 

■which  is  fitted  by  a  cork  into  one  of  the  tubulatures  of  a  large 
WoolfTs  bottle,  the  bottom  of  which  it  almost  touches.  In 
the  other  neck  of  the  bottle  a  cork  is  also  fitted,  which  con- 
tains a  short  glass  tube  bent  at  the  top  ;  this  is  connected  by 
a  flexible  tube  with  the  stem  of  a  T-shaped  tube,  one  branch 
of  which  leads  to  a  manometer,  the  other  to  a  second  smaller 
"WoolfTs  bottle,  in  which  the  injection  mass  is  contained.  The 
long  flexible  tube  which  leads  from  the  suspended  bottle  must 
be  furnished  with  a  clamp,  and  another  is  required  on  the  tube 
which  connects  the  T  with  the  injection-flask.  Another  ar- 
rangement consists  of  a  large  flask  holding  several  gallons,  in 
the  mouth  of  which  a  large  India-rubber  stopper  can  be  fitted. 
At  the  bottom  there  is  a  side  tubulature  (for  discharging  the 
water  when  necessary),  into  which  a  second  stopper  must  be 
fitted.  The  stopper  contains  a  strong  glass  tube,  having  a  bit 
of  India-rubber  tube  fitted  to  it,  guarded  by  a  strong  clamp. 
In  the  large  stopper  are  two  glass  tubes,  one  of  which  is  short, 
not  extending  beyond  the  neck,  and  bent  at  the  top;  it  is  con- 
nected with  a  T  tube,  which  corresponds  to  the  one  employed 
in  the  apparatus  first  described.  The  second  tube  is  of  the 
same  form  as  the  first,  and  communicates  with  a  supply-tap. 
In  other  forms  of  apparatus  rnercury  is  used.  The  apparatus 
may  then  consist  merely  in  a  single  WoolfTs  bottle,  into  one 
of  the  necks  of  which  a  rose  funnel  is  fitted,  reaching  to  the 
bottom.  The  other  neck  contains  a  short  bent  glass  tube, 
which  communicates  with  the  T  tube  as  before.'  In  all  forms 
of  apparatus  for  injection,  it  is  necessary  to  take  the  greatest 
care  to  make  all  the  junctions  absolutely  air-tight. 

The  injection  mass  is  always  contained  as  above  described 
in  a  WoolfTs  bottle,  which  should  be  previously  graduated,  so 
that  the  operator  may  know  as  he  proceeds  how  much  has 
been  injected.  One  of  the  necks  of  the  bottle  is  in  communi- 
cation with  the  T  tube,  by  means  of  a  short  glass  tube  fitted 
with  a  caoutchouc  connector,  which  does  not  reach  below  the 
vulcanite  stopper  in  which  it  is  fixed.  In  the  other,  a  long 
tube  is  contained,  the  end  of  which  reaches  to  the  bottom  of 
the  bottle,  while  the  top  communicates  with  the  canula.  If  a 
metal  canula  is  used,  the  India-rubber  tube  is  fitted  on  to  the 
stopcock.  If  the  canula  is  of  glass,  it  is  guarded  by  a  screw- 
clamp. 

When  the  organ  or  animal  to  be  injected  is  small,  it  answers 
well  to  use  the  syringe  as  a  compression  air-pump,  by  con- 
necting it  with  the  short  tube  of  the  WoolfTs  bottle.  The 
superiority  of  this  method  over  the  direct  use  of  the  syringe 

1  Of  the  more  complicated  forms  of  mercurial  apparatus,  that  devised 
by  Hering  (which  is  to  be  had  of  Heinitz,  instrument  maker  in  Vienna) 
is  undoubtedly  the  best,  and  answers  all  requirements.  A  description 
of  it  will  be  found  in  the  Wiener  Sitzungsberichte. 


116  VASCULAR   SYSTEM. 

is  obvious.  The  inequalities  of  the  pressure,  which  are  its 
chief  disadvantage,  are  annulled  by  the  elasticity  of  the  air 
contained  in  the  bottle,  which  serves  as  a  kind  of  cushion. 
'While  the  operator  fixes  his  attention  on  the  canula,  an 
assistant  gradually  injects  air  into  the  bottle  until  the  con- 
tents of  the  syringe  are  discharged.  The  tube  must  then  be 
closed  with  a  screw-clamp,  and  the  operation,  if  necessary, 
repeated. 

"When  warm  masses  are  used,  it  is  commonl}'  necessary  to 
place  the  injection-bottle  in  a  water-bath,  kept  warm  by  a 
spirit  lamp.  It  is  also  desirable  to  keep  the  object  warm,  for 
which  purpose  it  is  placed  on  a  plate  of  glass  over  a  water- 
bath ;  or  (as  in  Ludwig's  arrangement)  a  warm  chamber  of 
metal  supported  on  a  tripod  is  used,  which  is  large  enough  to 
hold  both  the  animal  and  the  bottle  containing  the  injection. 
It  is  furnished  with  a  cover  and  air  opening  for  the  admission 
of  the  compressed  air. 

In  order  to  illustrate  the  method  more  completely,  I  will 
describe  three  injections.  In  the  first  of  these  examples  the 
syringe  is  used  in  the  ordinary  way ;  in  the  second  it  serves 
as  a  pump  for  the  injection  of  air  into  the  "WoolrTs  bottle  con- 
taining the  mass;  in  the  third,  the  apparatus  is  used.  Sup- 
pose that  it  is  desired  to  inject  the  kidneys  of  a  small  mammal 
with  cold  two  per  cent,  solution  of  Prussian  blue.  The  animal 
having  been  just  killed  by  bleeding,  the  abdomen  is  opened 
and  the  whole  mass  of  intestines  pushed  aside  to  the  right. 
The  left  renal  artery  is  then  separated  from  surrounding  parts 
with  the  aid  of  two  pairs  of  ordinary  forceps  without  any  cut- 
ting instrument.  A  silk  ligature  is  placed  round  the  artery, 
and  looped  near  to  the  point  at  which  it  enters  the  kidney. 
The  vein  is  next  prepared  in  the  same  way,  and  a  ligature 
placed  round  it  close  to  its  junction  with  the  vena  cava.  By 
drawing  on  the  renal  vein,  it  is  easy  to  make  a  valvular  open- 
ing with  fine  scissors.  The  artery  is  similarly  opened  short 
of  the  loop,  and  the  metal  canula  with  its  stopcock  intro- 
duced, the  edge  of  the  incision  being  held  aside  with  the  for- 
ceps. In  making  the  opening  and  inserting  the  canula,  the 
greatest  care  must  be  taken  to  avoid  rupturing  the  artery  or 
cutting  it  through  with  the  scissors.  The  moment  that  the 
canula  is  in  the  artery,  the  loop  must  be  tightened  round  the 
groove.  The  canula  and  nozzle  are  then  filled  with  half  per 
cent,  salt  solution  with  the  aid  of  a  capillary  tube  :  the  syringe 
is  charged  with  the  liquid  and  connected  with  the  nozzle.  In 
injecting,  the  piston  must  be  slowly  pushed  forwards.  As 
soon  as  the  organ  becomes  blue,  and  the  liquid  appears  to  pass 
unmixed  from  the  opening  in  the  vein,  I  stop,  and  then  direct 
my  assistant  to  close  the  vein  with  a  clip,  or  to  tighten  a  loop 
previously  placed  round  the  vessel  for  this  purpose.     This 


BY   DR.    KLEIN.  117 

done,  I  make  one  push  more  with  the  piston,  turn  the  stop- 
cock of  the  nozzle,  and  take  away  the  syringe. 

I  will  next  describe  the  injection  of  a  whole  animal,  such  as 
a  rat  or  a  small  rabbit,  with  carmine  gelatin  mass.  The  animal 
is  killed  b}-  inhalation  of  chloroform.  A  window  is  then  cut 
out  in  the  left  wall  of  the  chest,  just  large  enough  to  expose 
the  heart  and  the  roots  of  the  great  vessels,  taking  care  not  to 
carry  these  incisions  so  near  the  middle  line  as  to  endanger 
the  internal  mammary  artery.  A  fold  of  pericardium  having 
been  taken  up  with  the  forceps  and  divided,  the  apex  of  the 
heart  is  raised  out  of  the  thorax  and  pierced  with  a  threaded 
needle  through  both  ventricles.  By  the  thread  which  has  been 
brought  through,  the  apex  is  then  drawn  downwards  by  an 
assistant,  while  the  root  of  the  aorta  is  cleared  with  the  aid  of 
two  pairs  of  dissecting  forceps.  A  ligature  is  then  passed 
round  it  close  to  its  origin,  and  looped.  Thereupon  the  wall 
of  the  left  ventricle  is  opened  near  its  base,  and  as  soon  as 
blood  has  ceased  to  flow,  the  canula  is  passed  into  the  aorta, 
to  such  a  distance  that  its  neck  can  be  grasped  by  the  ligature, 
which  is  then  tightened.  The  blood  in  the  canula  is  then  re- 
moved with  a  capillary  pipette,  and  filled  with  saline  solution 
with  another  pipette,  and  an  opening  is  made  in  the  right 
ventricle.  Up  to  this  time  the  animal  has  been  allowed  to 
remain  on  a  plate.  The  plate  is  now  placed  on  a  support,  at 
a  level  which  nearly  corresponds  with  that  of  the  WoolfFs 
bottle,  in  which  the  mass  is  contained,  which  is  kept  warm  by 
immersion  in  a  water-bath,  heated  by  a  spirit  lamp.  The  noz- 
zle having  been  connected  with  the  discharge  tube  of  the  flask 
by  an  India-rubber  tube,  and  the  syringe  (the  piston  of  which 
has  been  drawn  up)  with  the  other  opening  in  the  WoolfTs 
bottle,  an  assistant  injects  a  little  air  so  as  to  fill  the  discharge 
tube  up  to  the  orifice  of  the  nozzle.  The  stopcock  is  then 
closed,  and  the  point  of  the  nozzle  inserted  in  the  canula. 
The  stopcock  having  been  reopened,  the  assistant  pushes  on 
the  piston.  As  soon  as  the  syringe  is  emptied,  the  screw-clamp 
between  it  and  the  injection  bottle  is  tightened.  Air  is  again 
injected,  if  necessary,  in  the  same  manner.  If,  however,  a  full- 
sized  syringe  is  used,  it  is  seldom  necessary  to  repeat  the  pro- 
cess. When  the  vessels  are  sufficiently  full,  the  heart  is 
seized  with  strong  clip-forceps,  as  near  the  base  as  possible, 
care  being  taken  not  to  include  the  canula.  The  stopcock  is 
then  closed. 

As  a  third  example  may  be  taken  the  injection  of  the 
abdominal  organs  of  a  rabbit.  The  animal  is  decapitated. 
The  whole  of  the  left  wall  of  the  thorax  is  removed  from  the 
flanks  forwards  as  far  down  as  the  costal  origin  of  the  anterior 
half  of  the  diaphragm.  The  left  lung  and  the  heart  having 
been  drawn  aside  to  the  right,  the  thoracic  aorta  is  prepared 


118  VASCULAR   SYSTEM. 

with  two  pairs  of  dissecting  forceps  as  far  down  as  possiMe. 
A  ligature  having  been  passed  round  the  vessel  and  looped, 
and  the  vessel  slit  open,  the  canula  is  introduced  and  the 
ligature  tightened.  The  canula  having  been  then  cleared  of 
blood  and  filled  with  saline  solution,  the  plate  on  which  the 
animal  lies  is  put  into  the  warm  chamber  which  contains  the 
injection  bottle.  This  bottle,  which  is  charged  with  the  warm 
Prussian  blue  mass,  is  connected  with  the  pressure  bottle,  the 
manometer  of  which  indicates  a  pressure  of  00  to  120  milli- 
metres. It  is,  however,  not  in  communication  with  it,  for  the 
connecting  tube  is  closed  by  a  clamp.  This  clamp  is  then 
slightly  opened  for  a  moment,  so  as  to  fill  the  discharge  tube 
to  the  orifice,  and  immediately  closed,  the  stopcock  being 
shut  at  the  same  time.  The  nozzle  having  been  inserted  into 
the  canula,  the  stopcock  and  clamp  are  simultaneously 
opened.  The  cover  of  the  chamber  is  put  on  and  the  injection 
allowed  to  proceed,  all  that  is  required  being  to  maintain  the 
pressure  in  the  apparatus  as  nearly  constant  as  possible. 
When  the  injection  is  complete,  a  clip  is  placed  on  the  vena 
cava,  near  its  mouth,  and  the  stopcock  shut.  [The  special 
methods  to  be  used  for  the  injection  of  particular  organs,  and 
the  methods  of  double  injection,  will  be  given  under  the  proper 
heads.] 

Injection  with  Solution  of  Nitrate  of  Silver. — It  is 
preferable  for  this  purpose  to  work  with  the  apparatus,  as  it 
is  necessary  to  employ  a  considerable  pressure.  As  soon  as 
the  injection  is  completed,  it  must  be  replaced  by  water.  This 
is  effected  by  substituting  a  flask  containing  water  fo  rthat 
used  for  the  nitrate  of  silver  solution.  The  vessels  must  be 
thoroughly  streamed  with  water,  otherwise  the  endothelial 
markings  are  concealed  by  the  quantity  of  precipitate  which 
is  formed. 

Treatment  of  Injected.  Tissues. — Organs  injected  with 
colored  masses  must  be  suspended  in  ordinary  alcohol  in  a 
breaker.  If  a  whole  animal  has  been  injected,  the  body  must 
be  left  to  cool  for  half  an  hour  or  more.  It  must  then  be  trans- 
ferred to  a  large  vessel  containing  common  alcohol,  to  which 
a  few  drops  of  glacial  acetic  acid  have  been  added.  It  is  a 
good  plan  to  transfer  animals  which  have  been  injected  with 
gelatin  masses  to  ice-cold  alcohol,  immediately  after  the  com- 
pletion of  the  injection;  great  care  being  taken  in  this,  as  in 
every  other  case,  to  secure  the  artery  and  vein  so  as  to  avoid 
all  risk  of  escape  of  the  mass. 

Section  II. — Structure  op  the  Bloodvessels. 

Endothelium. — The  simplest  method  of  demonstration  is 
to  color  the  internal  surface  with  silver.     If  the  vessels  are  of 


BY    DR.    KLEIN.  119 

large  size,  they  are  prepared  as  follows:  A  portion  of  the 
vessel  taken  from  the  freshly  killed  animal  is  washed  with  di- 
luted serum  and  then  dipped  for  a  few  minutes  in  half  per 
cent,  solution  of  silver.  Its  internal  surface  is  then  exposed 
to  light  until  it  acquires  a  brownish-yellow  color.  If  the  mus- 
cular wall  is  thick,  the  intima  must  be  separated  by  the  meth- 
od previously  described  (Chapter  III.  p.  48)  and  covered  in 
gh'cerin,  with  its  endothelial  surface  upwards.  If  the  vessel 
is  thin-walled,  e.  y.,  the  vena  cava  of  a  small  animal,  it  can  be 
covered  without  an}r  preparation.  For  the  endothelium  of 
capillaries  in  the  kidney  or  bladder,  or  in  the  serous  mem- 
branes, the  best  results  are  obtained  by  injection  of  the  solu- 
tion of  nitrate  of  silver.  In  the  serous  membranes,  however, 
e.  <j.,  in  the  mesenter}",  good  preparations  can  be  obtained  by 
first  pencilling  one  or  both  surfaces  with  fresh  serum  in  situ 
(the  animal  having  been  bled  to  death)  and  then  cutting  out 
the  pencilled  part  and  coloring  in  silver  in  the  usual  way 

The  endothelium  of  the  large  arteries  consists  of  long  nar- 
row spindle-shaped  \  lates.  The  nucleus  is  oblong,  and  usual- 
ly in  the  middle  of  each  plate.  The  interstitial  lines  are  very 
slightly  sinuous.  The  endothelial  elements  of  the  veins  are 
relatively  broader.  If  the  staining  is  intense,  the  cell  is  filled 
with  brown  precipitate,  the  nucleus  remaining  clear.  The  ca- 
pillary vessels  appear,  when  colored  with  silver,  to  consist 
merely  of  oblong  plates,  the  interstitial  lines  of  which  are  com- 
monly more  or  less  sinuous.  The  oblong  regular  nuclei  of  the 
walls  of  the  capillaries  seen  in  profile  are  those  of  the  endo- 
thelium elements.  It  is  easy  to  color  the  nuclei  by  carmine, 
in  which  case  an  acid  solution  must  be  used,  i.  e.,  an  ammoni- 
acal  solution  to  which  a  sufficient  quantity  of  acetic  acid  has 
been  added  to  render  it  distinctly  acid.  Larger  vessels  must 
be  immersetl  in  the  solution,  but  for  capillaries  it  is  enough  to 
immerse  the  membrane  in  which  they  are  contained.  Ten 
minutes'  immersion  is  sufficient  for  the  purpose:  the  prepara- 
tion must  then  be  washed  in  water  and  prepared  in  glycerin. 
In  preparations  of  mesentery  of  the  frog  or  of  a  small  mamma- 
lian animal  in  bichromate  of  potash,  the  nuclei  may  be  readily 
recognized,  not  only  in  profile,  but  on  the  surface  of  the  small 
vessels. 

The  Intima- — The  anatomical  relations  of  the  intima,  i.  e., 
of  the  internal  longitudinal  fibres,  and  the  elastic  membrane, 
may  be  studied  either  in  sections  or  in  the  fresh  state.  In 
large  arteries,  the  best  method  is  to  immerse  the  vessel  in  one 
per  cent,  solution  of  bichromate  for  several  days.  The  intima 
is  then  peeled  off  in  thin  strips,  which  are  teased  in  the  same 
liquid  and  covered  with  gl}rcerin.  This  is  the  only  way  of 
showing  the  elastic  network  or  the  fenestrated  membrane 
which  exists  in  certain  arteries.     In  vessels  of  macroscopical 


120  VASCULAR   SYSTEM. 

dimensions,  e.  g.,  in  large  arteries  of  the  mesentery,  the  intima 
is  seen  in  profile  both  in  fresh  preparations  and  after  treatment 
with  bichromate  of  potash,  as  a  doubly-contoured,  sharply  de- 
fined membrane;  the  surface  view  showing  traces  of  longitu- 
dinal fibres.  In  cross  sections  of  smaller  arteries,  the  intima 
is  seen  as  a  wavy  hyaline  membrane,  differing  in  thickness 
according  to  the  size  of  the  artery.  The  intima  of  large  veins 
differs  only  in  its  thickness  from  that  of  the  arteries. 

Muscular  Coat. — The  muscular  coat  differs  in  its  charac- 
ters in  different  parts  of  the  vascular  system.  In  the  arteries, 
the  muscular  elements  form  layers  which  are  connected  to- 
gether by  the  elastic  lamella?  interposed  between  them,  the  two 
together  constituting  the  tunica  media.  In  many  arteries 
there  are  also  bundles  of  muscular  fibres  in  the  intima,  and  in 
others  in  the  adventitia.  In  the  minute  arteries  they  form  cir- 
cular layers,  the  number  of  which  varies  according  to  the  size 
of  the  vessel.  In  such  arteries  the  media  is  made  up  almost 
entirely  of  muscular  fibres. 

The  muscular  fibres  of  large  arteries  may  be  studied  either 
by  teasing  preparations  of  vessels  steeped  in  bichromate  of 
potash,  or  in  sections  hardened  in  chromic  acid.  The  muscle- 
cells  of  large  arteries  appear,  when  isolated,  to  be  broader, 
relatively,  than  ordinary  muscular  elements,  and  are  often  split 
at  their  ends  into  processes.  The  oblong  nuclei  are  more  or 
less  staff-shaped.  If  a  portion  of  fresh  bladder  of  the  frog  is 
treated  with  acetic  acid  in  the  manner  already  recommended 
in  the  chapter  on  unstriped  muscular  fibres,  or  a  portion  of 
mesentery  of  a  frog  or  mammal  with  bichromate  of  potash  or 
acetic  acid,  the  muscle-cells  can  be  distinguished  as  trans- 
versely arranged  short  spindles,  inclosing  long  distinctl}*  gran- 
ular staff-shaped  nuclei,  which  are  arranged  in  rows  alternating 
with  each  other.  In  optical  longitudinal  sections  of  minute 
arteries,  such  as  occur  very  frequently  in  sections  of  hardened 
tissues,  the  elements  of  the  media  exhibit  the  same  appear- 
ances as  in  cross  sections  of  involuntary  muscle  in  general ;  as, 
however,  the  muscle-cells  are  shorter,  and  their  nuclei  longer, 
most  ctoss  sections  exhibit  a  nucleus  in  almost  every  element. 
In  minute  veins,  muscular  elements  are  seen  which  have  a  longi- 
tudinal direction,  but  do  not  form  a  continuous  layer.1 

The  intima  and  adventitia  of  the  bloodvessels  contain  nu- 
merous branched  cells.  To  demonstrate  them,  sections  must 
be  made  of  bloodvessels  and  treated  with  gold.  They  ma}r  be 
also  shown  in  preparations  made  by  the  silver  method.  By  this 
method  a  rich  network  of  lymphatics  may  be  demonstrated  in 
the  adventitia  of  the  aorta  of  small  animals. 

1  For  the  special  arrangements  of  the  muscular  fibres  in  particular 
arteries,  the  reader  is  referred  to  larger  treatises  on  general  anatomy. 


BY    LR.    KLEIN.  121 

Nerves. — The  rich  plexus  of  non-medullated  nerve  fibres 
which  exists  in  the  adventitia  of  large  bloodvessels,  can  be 
studied  in  the  mesentery  of  the  frog,  which  for  this  purpose 
must  be  prepared  in  the  manner  directed  in  Chapter  V.  for  the 
demonstration  of  the  nerves  of  the  mesentery.  In  the  same 
organ  it  can  be  shown  that  the  capillaries  are  also  surrounded 
by  non-medullated  nerve  fibres.  In  the  nictitating  membrane 
and  tongue  of  the  frog,  the  plexuses  which  surround  the  capil- 
laries may  be  seen  to  give  out  fibrils  which  enter  the  walls  of 
the  vessels  themselves.  For  this  purpose  the  tongue  of  the 
frog  must  be  colored  in  a  half  per  cent,  solution  of  chloride  of 
gold,  and  used,  after  hardening  in  alcohol,  for  the  preparation 
of  sections.     (See  Chapter  XII.) 

The  development  of  bloodvessels  will  be  given  in  the  chapter 
on  Embryology. 

Section  III.— Microscopical.  Study  of  the  Circulation. 

Study  of  the  Circulation  in  Cold-blooded  Animals. 

— The  parts  which  may  be  used  for  this  purpose  are  (1)  the 
web  of  the  frog's  foot,  (2)  the  mesentery  of  the  frog  or  toad, 
(3)  the  tongue  of  the  same  animal,  (4)  the  tadpole. 

Web  of  the  Frog. — If  the  animal  is  not  curarized,  the 
arrangement  must  be  employed  which  was  described  in  Chap- 
ter III.  It  is,  however,  better  to  employ  curare,  as  described 
in  Chapter  XVII.  The  animal  is  laid  on  an  oblong  plate  of 
glass,  on  which  a  cork  disk  is  fixed  with  sealing-wax,  which 
should  be  three-tenths  of  an  inch  thick,  and  an  inch  and  a 
quarter  wide.  The  disk  must  have  a  hole  in  the  middle,  which 
should  be  about  three-quarters  of  an  inch  wide.  At  the  edge 
of  this  aperture  pins  are  stuck,  to  which  ligatures  attached  to 
the  toes  may  be  secured. 

Mesentery". — The  preparation  of  the  mesentery  is  not  so 
simple.  A  snip  is  made  in  the  right  side  of  the  belly,  parallel 
with  the  middle  line.  Before  dividing  the  skin  further,  it  is 
raised  to  ascertain  where  there  are  no  large  veins  ;  the  incision 
is  then  continued  upwards  and  downwards,  in  such  directions 
as  to  avoid  bleeding.  If,  notwithstanding,  a  vein  is  divided, 
the  bleeding  must  be  restrained  by  seizing  the  end  of  the  in- 
cision with  the  clip-forceps.  The  traces  of  blood  having  been 
removed  with  filter  paper,  the  muscles  are  divided  in  the  same 
vertical  line.  This  having  been  done,  the  intestine  and  mesen- 
tery are  drawn  out  carefully,  and  laid  on  the  anterior  surface 
of  the  belly.  The  next  step  is  to  place  the  animal  on  a  in  Fig. 
19.  (For  this,  however,  a  simple  glass  plate  of  similar  size 
may  be  substituted,  nt  the  edge  of  which  a  cork  is  fixed,  which 
should  have  an  aperture  corresponding  to  c,  covered  with  a 
round  cover-glass.)     The  frog  having  been  pushed  up  against 


122  VASCULAR   SYSTEM. 

rf,  the  intestine  can  be  easily  turned  over  on  to  b.  The  intes- 
tine then  lies  in  the  trough  c,  while  the  mesentery  rests  on  the 
glass  plate  b.  So  much  of  the  intestine  as  does  not  occupy  the 
trough  must  be  replaced.  If  the  observation  is  prolonged  i  as 
in  researches  on  inflammation),  it  is  well  to  place  in  the  trough, 
outside  of  the  intestine,  a  layer  of  Alter  paper,  on  which  half 
per  cent,  solution  of  salt  is  dropped  from  time  to  time.  It  is 
sometimes  useful,  when  high  powers  are  to  be  employed,  to 
cover  the  mesentery  with  thin  glass.  If  the  cork  is  used,  it  is 
necessary  to  fix  the  intestine  at  two  or  three  points  with  small 
pins'. 

Tongue. — The  animal  must  be  curarized  as  before.  A  plate 
of  glass,  like  that  used  for  the  web,  is  employed,  with  this 
difference,  that  the  cork,  instead  of  having  a  round  aperture, 
is  cut  into  the  form  of  a  horseshoe,  the  convexity  of  which  is 
towards  the  edge  of  the  plate.  If  it  is  intended  to  study  the 
circulation  on  the  lower  surface  of  the  tongue,  the  animal  is 
placed  on  its  belly.  If  the  papillary  surface  is  to  be  examined, 
it  must  be  on  its  back.  In  either  case,  the  tongue  must  be 
drawn  out  by  the  cornua,  around  each  of  which  a  thread  must 
be  secured.  With  the  aid  of  these  threads  the  organ  is  drawn 
as  forward  as  possible  without  affecting  the  circulation,  and 
secured  to  pins  which  are  stuck  horizontally  into  the  edge  of 
the  cork  at  each  corner.  It  is  sometimes  necessary  to  extend 
the  organ  further  by  means  of  pins  stuck  in  the  cork  at  the 
sides. 

Tail  of  the  Tadpole. — The  tail  of  the  tadpole  affords  a 
most  instructive  object.  The  animal  is  curarized  by  placing 
it  in  a  drop  or  two  of  solution  in  a  watch  glass.  As  soon  as 
it  is  motionless  it  is  transferred  to  an  object-glass  and  ex- 
amined. The  description  of  the  phenomena  of  circulation  as 
seen  in  the  batrachians,  and  of  the  methods  employed  for  their 
investigation  in  mammalia,  will  be  found  in  Chapter  XVII. 

Observation  of  the  Emigration  of  Colored  and 
Colorless  Blood  Corpuscles. — In  the  tadpole,  emigration, 
particularly  of  the  colored  corpuscles,  may  be  witnessed  in 
various  parts  of  the  tail,  if  the  observation  is  continued  for 
a  short  time.1  If  the  mesenteiy  of  a  frog  is  exposed  to  the 
air,  or  treated  with  any  irritant,  the  emigration  of  colorless 
corpuscles  can  be  seen  with  the  greatest  ease,  provided  that 
the  observation  is  made  with  sufficient  care.  A  small  vein 
must  be  sought  out  with  a  low  power,  and  a  point  selected  in 
its  course  at  which  one  or  more  colorless  corpuscles  have 
attached  themselves  to  the  walls.  These  must  then  be  watched 
continuously  under  a  higher  power. 

1  In  the  frog  an  abundant  emigration  of  colored  corpuscles  takes 
place  after  the  injection  of  salt  solution  (two  to  six  per  cent.). 


BY    DR.    KLEIN.  123 


CHAPTER  VIII. 

LYMPHATIC  SYSTEM. 
Section  I. — Lymphatic  Vessels. 

The  tymphatic  vessels  may  be  studied  either  by  coloring 
with  nitrate  of  silver  or  by  injection.  As  those  of  the  serous 
membranes  are  most  readily  demonstrated,  it  will  be  con- 
venient to  refer  to  them  first. 

Lymphatics  of  the  Centrum  Tendineum  of  the 
Diaphragm. — The  pleural  cavity  of  a  rabbit  or  guinea-pig, 
which  has  just  been  killed,  is  exposed  by  removing  the  sternum, 
care  being  taken  to  avoid  opening  any  large  bloodvessels. 
The  pleura  having  then  been  divided  along  the  edge  of  the 
costal  part  of  the  diaphragm,  the  cava  ascendens  is  ligatured 
close  to  the  atrium,  and  divided  between  the  ligature  and  the 
heart.  The  heart  and  lungs  are  then  removed  from  the 
thoracic  cavit}7.  The  pleural  side  of  the  centrum  tendineum  is 
then  carefully  brushed  with  a  camel-hair  pencil,  moistened  with 
serum,  after  which  a  small  quantity  of  half  per  cent,  solution 
of  nitrate  of  silver  is  poured  on  the  diaphragm,  while  the 
animal  is  held  vertically,  with  its  head  uppermost.  After  five 
minutes  or  so,  the  silver  solution  is  poured  av,ray  and  replaced 
bj*  water,  which  should  be  changed  several  times.  The  centrum 
tendineum  may  then  be  cut  out  and  prepared  in  glycerin.  Ac- 
cording to  another  plan,  the  diaphragm  is  cut  out  immediately 
after  it  has  been  brushed,  and  immersed  in  solution  of  nitrate 
of  silver.  With  this  view  the  abdominal  cavity  is  opened;  the 
ligamentum  suspensorium  is  divided,  and  a  ligature  placed 
round  the  vena  portce.  This  vein,  having  been  divided,  the 
whole  diaphragm  is  cut  out  with  the  liver.  In  such  a  prepara- 
tion clear  channels  are  seen  in  the  yellowish-brown  ground- 
substance,  which  are  of  various  size,  and  of  two  kinds,  and 
exhibit  endothelial  markings.  In  the  one  kind — viz.,  in  the 
larger  vessels — the  endothelial  elements  are  spindle-shaped; 
in  the  other — i.  e.,  the  capillaries — they  are  more  or  less  sin- 
uous. The  walls  of  all  these  vessels  consist  exclusively  of 
endothelium. 

Before  describing  the  arrangement  of  the  lymphatics  in  the 
centrum  tendineum,  it  is  desirable  to  give  an  account  of  the 
structure  of  that  organ.  It  consists  of  three  parts,  viz.,  pleura, 
peritoneum,  and  tendon ;  each  serous  membrane  being  made 


124  LYMPHATIC    SYSTEM. 

up  of  endothelium  and  membrana  propria.  The  tendon  con- 
sists of  two  layers,  of  which  the  one  that  is  next  the  perito- 
neum is  formed  of  bundles  of  fibres  which  radiate  from  the 
centre  outwards;  the  upper  Layer  of  bundles  arranged  circu- 
larly. The  bundles  of  each  are  separated  from  their  neighbors 
by  splits  or  channels,  of  which  there  are  two  sets;  those 
between  the  abdominal  layers  being  designated  the  superficial, 
those  of  the  pleural,  the  deep  interfascicular  channels  of  the 
centrum  tendineum.  The  membrana  propria  of  the  peritoneum, 
where  it  stretches  over  the  superficial  channels,  possesses  a 
special  fenestrated  structure  (found  also  in  one  or  two  situa- 
tions elsewhere).  Between  the  propria  of  the  pleural  side  and 
the  tendons,  large  lymphatic  vessels  exist  which  form  numer- 
ous ramifications,  and  communicate  with  a  network  of  capil- 
laries. All  of  the  larger  vessels  are  provided  with  valves, 
with  their  corresponding  dilatations.  The  capillaries  may  be 
distinguished  into  those  which  lie  in  the  pleural  propria,  and 
have  a  more  or  less  winding  course,  and  those  which  are 
straight  and  lie  further  from  the  pleural  surface.  The  former 
have  saccular  dilatations,  which  are  called  lymphatic  sinuses. 
The  straight  vessels  are  contained  in  the  channels  already 
described,  and  may,  therefore,  be  designated  lymphatics  of 
the  interfascicular  channels.  They  may  be  further  distin- 
guished, according  as  they  are  contained  in  the  peritoneal  or 
pleural  layer,  into  superficial  and  deep.  There  are  many 
channels  of  both  layers  which  do  not  contain  them.  The  two 
sets  of  vessels  are  in  communication  with  each  other.  The 
superficial  interfascicular  lymphatics  pass,  in  the  neighborhood 
of  the  great  vessels  which  perforate  the  centrum  tendineum, 
into  winding  lymphatic  capillaries  with  saccular  dilatations, 
which  are  situated  on  the  abdominal  surface  of  the  tendon, 
where  the}'  form  a  network.  On  the  other  hand,  the  interfas- 
cicular lymphatics  freely  communicate  with  the  peritoneal 
cavity  by  means  of  vertical  channels,  which,  although  they  for 
the  most  part  extend  only  to  the  radiating  tymphatics  of  the 
superficial  layer,  can  also,  in  many  instances,  be  seen  to  pass 
directly  to  those  contained  in  the  deeper,  i.  e.,  the  circular 
channels.  By  these  canals  the  endothelium  of  the  lymphatics 
is  continuous  with  that  of  the  peritoneum.  The  endothelial 
elements  which  guard  the  orifices  of  each  vertical  canal  (the 
stoma)  have  the  characters  of  young  cells,  and  differ  from 
those  which  adjoin  them  in  being  more  granular,  smaller,  and 
polyhedric.  It  has  been  already  indicated,  in  Chapter  II., 
that  the  endothelium  which  covers  the  channels  consists  of 
smaller  and  apparent^  3'ounger  elements  than  those  of  the 
general  surface.  These  characters  are  much  more  marked  in 
the  cells  which  surround  and  form  the  stomata.  Iu  diaphragms 
which  have  been   stained  without   brushing,  they  cannot   be 


BY    DR.    KLEIN.  125 

made  out.  It  is  true  that,  among  the  small  mosaic  of  certain 
channels,  there  are  dark  or  clear  spots  which  have  been  de- 
scribed by  authors  as  stomata,  with  which,  however,  their 
relation  is  very  doubtful. 

Method  of  Demonstrating  the  Stomata. — To  demon- 
strate them,  the  abdominal  cavity  of  a  rabbit  just  killed  must 
be  opened,  a  ligature  passed  round  the  cardia,  and  another 
round  the  bunch  of  vessels  leading  to  the  porta.  This  done, 
the  abdominal  viscera,  excepting  the  liver,  may  be  cut  away 
and  removed;  great  care  being  taken  not  to  draw  upon  the 
diaphragm  in  any  part  of  the  operation.  The  liver  being  then 
held  aside,  water  is  poured  over  the  abdominal  surface  of  the 
diaphragm.  After  a  few  seconds,  silver  solution  is  poured 
once  or  twice  over  it  in  the  same  wa}',  and  the  whole  left  to 
itself  for  a  few  minutes.  It  is  then  again  washed  with  water, 
after  which  it  may  be  cut  out  and  subjected  to  microscopical 
examination.  In  preparations  so  obtained  rows  of  stomata 
may  be  seen,  both  over  the  superficial  interfascicular  lymph- 
atics, and  occasionally  in  situations  which  correspond  to  the 
circular  ones  ;  which,  exhibit,  in  all  respects,  the  same  anato- 
mical characters  as  those  of  the  septum  cisternee  magnee  in  the 
frog.  Each  canal  leading  from  a  stoma  to  a  subjacent  lym- 
phatic is  seen  to  be  lined  by  small  granular  cells  of  the  same 
character  as  those  already  described  as  guarding  the  orifice. 
They  are  particularly  distinct  where  the  canal  opens  into  the 
13-mphatic,  especially  in  those  canals  which  are  in  communica- 
tion with  the  lymphatics  of  the  deeper,  i.  e.,  the  pleural  layer. 
The  lymphatic  system  of  the  diaphragm  is  divisible  b}-  the 
middle  line  into  two  similar  halves.  Each  half  may  be  again 
divided,  according  to  the  direction  in  which  the  lymph  flows, 
into  two  parts — an  anterior  and  a  posterior.  The  anterior 
system  is  made  up  of  the  large  lymphatic  vessels  to  be  found 
on  the  pleural  side,  all  of  which  converge  towards  the  sternum, 
discharging  themselves  into  a  single  large  lymphatic  trunk, 
which  stretches  in  the  form  of  an  arch  along  the  outer  edge  of 
the  sternum,  accompanying  the  internal  mammary  artery  and 
vein. 

Each  of  the  trunks  as  it  ascends  divides  into  a  plexus  of 
smaller  vessels,  by  which  the  lymph  is  conveyed  to  the  sternal 
glands.  These  lymph  vessels  receive  their  tributaries  from 
the  external  border  of  the  anterior  half  of  the  centrum,  and 
from  the  anterior  third  of  the  external  border  of  the  posterior 
half.  The  lymphatic  vessels  of  the  remainder  of  the  diaphragm 
belong  to  the  posterior  system,  which  opens  on  either  side  by 
a  short,  wide  lymphatic  trunk,  which  joins  the  thoracic  duct 
just  after  the  latter  has  entered  the  throracic  cavity.  The 
lymphatic  interfascicular  channels  are  all  to  be  regarded  as 
tubes   of  communication  between  the  two   systems.      From 


126  LYMPHATIC    SYSTEM. 

these  facts  it  ma}'  he  understood  why  the  posterior  half  of 
the  diaphragm  is  more  readily  filled  from  the  peritoneum  than 
the  anterior. 

Demonstration  of  the  Lymphatic  System  of  the 
Diaphragm  by  Injection. — In  a  large  or  middle-sized  rabbit, 
which  has  been  kept  from  sixteen  to  twenty  hours  without 
food,  ten  cubic  centimetres  of  a  warm,  five  per  cent,  solution  of 
Prussian  blue  are  injected  into  the  abdominal  cavity  through 
a  small  canula,  with  the  aid  of  a  glass  tube  drawn  out  at  one 
end.  The  liquid  is  allowed  to  flow  in  of  itself.  After  three 
hours  and  a  half,  the  animal  is  bled  to  death  by  opening  the 
carotid  arteiy,  or  killed  by  strangling.  As  soon  as  the  body 
is  cool,  the  pleural  cavity  is  opened,  the  cava  ascendens  is  liga- 
tured just  before  it  enters  the  heart,  while  a  second  ligature  is 
tightened  round  the  aorta,  oesophagus,  thoracic  duct,  and  vena 
azygos.  The  vessels  having  been  divided  above  the  ligatures, 
the  whole  of  the  thoracic  viscera  are  removed.  With  a  lens  the 
arrangement  of  the  vessels  above  described  ma}r  now  be  made 
out,  without  removing  the  diaphragm.  To  obtain  permanent 
preparations,  the  peritoneal  cavity  must  be  opened,  and  the 
suspensory  ligament  divided  as  before  directed,  the  animal 
being  placed  aslant.  The  vena  cava  and  the  cardia  having 
next  been  divided  between  the  liver  and  the  diaphragm,  the 
serous  ligaments  which  connect  the  left  lobe  of  the  liver,  the 
stomach,  and  the  spleen  with  the  diaphragm,  are  severed,  so 
that  these  organs  are  complete^-  detached.  Thereupon  the 
abdominal  surface  of  the  centrum  tendineum  is  brushed  with  a 
camel-hair  pencil  moistened  with  warm  water,  after  which  the 
ring  of  bone,  cartilages,  and  soft  parts,  to  which  the  diaphragm 
is  attached  all  round,  is  separated  from  the  rest  of  the  body, 
immersed  for  a  few  minutes  in  silver,  and  washed  in  water. 
Those  parts  which  are  intended  for  microscopical  examination 
can  then  be  cut  out  and  covered  in  glycerin.  Anilin  and  milk 
may  be  used  in  the  same  manner  as  Prussian  blue,  but  do  not 
yield  such  certain  results. 

Another  method  of  injecting  the  lymphatics  of  the  diaphragm 
may  be  mentioned,  which  is,  however,  not  so  successful.  The 
liquid  employed  consists  either  of  one  or  two  per  cent,  solution 
of  Prussian  blue,  in  which  a  partial  fine  precipitation  has  been 
determined  by  the  addition  of  a  small  quantity  of  alcohol,  or 
of  anilin  with  milk.  A  rabbit  is  bled  to  death  by  opening  the 
crural  artery.  A  bent  tube  is  then  secured  in  the  trachea,  which 
is  connected  with  the  apparatus  for  artificial  respiration.  The 
abdominal  cavity  is  then  opened  and  the  suspensory  ligament 
divided,  as  well  as  the  fold  of  serous  membrane  which  connects 
the  left  lobe  of  the  liver  with  the  diaphragm.  The  cardia  having 
been  exposed  and  tied,  and  a  ligature  passed  round  the  vessels 
contained  in  the  omentum  minus  and  the  vena  cava  below  the 


BY    DR.    KLEIN.  127 

liver,  the  organs  are  cut  away  below  the  ligatures,  so  that  the 
diaphragm  is  covered  only  by  the  liver.  The  lumbar  part  of 
the  spinal  column  is  then  severed,  and  the  division  completed 
by  continuing  the  incision  forwards  on  either  side  to  the  middle 
line.  Threads  are  then  attached  to  the  cut  edges,  by  which 
the  upper  part  of  the  body  is  suspended,  head  downwards,  to 
a  ring  of  iron.  The  whole  operation  can  be  completed  in  from 
three  to  five  minutes.  The  next  step  is  to  pour  the  liquid  to 
be  used  (previously  warmed)  on  to  the  diaphragm,  in  quantity 
sufficient  to  cover  it.  For  twenty  or  thirty  minutes,  artificial 
respiration  is  maintained  at  regular  intervals.  The  diaphragm 
ma}'  then  be  prepared  as  before  for  microscopical  examination. 

The  Cellular  Elements  of  the  Centrum  Tendineum 
in  their  relation  to  the  Lymphatic  System. — The 
pleural  surface  of  the  centrum  lendineum  of  a  rabbit,  guinea- 
pig,  or  any  other  small  mammalian  animal,  is  exposed  as  above 
described,  and  carefully,  but  slightly,  brushed  with  a  camel- 
hair  pencil  moistened  with  serum.  Silver  solution  is  then 
poured  over  it,  and,  after  a  few  minutes,  water.  Thereupon  bits 
are  cut  out  for  microscopical  examination,  which  must  be  care- 
fully separated  from  the  parts  in  contact  with  their  abdominal 
surfaces.  These  must  then  be  mounted  in  glycerin,  with  the 
pleural  side  upwards.  Immediately  under  the  endothelium 
of  the  surface  there  exist  large,  flat  cells,  which  are  more  or  less 
branched.  In  the  neighborhood  of  the  large  vessels  which  pass 
through  the  centrum  tendineum  these  are  so  close  together  that 
they  are  marked  off  from  each  other  by  mere  lines  of  interstitial 
substance,  and  appear  as  if  they  formed  a  second  layer  of  flat 
endothelial  elements  subjacent  to  the  one  brushed  off.  Under 
these  cells  branched  cavities  are  seen  to  exist,  hollowed  out  in 
a  yellow  or  yellowish-brown  ground-substance.  When  the 
examination  is  made  with  sufficient  care,  it  is  found,  first,  that 
each  of  these  cavities  contains  a  nucleated  mass  of  protoplasm, 
which  completely  occupies  it;  and,  secondly,  that  both  the 
cavities  and  their  contents  are  in  continuit}'  with  each  other, 
so  as  to  form  a  network.  This  network  of  cavities  was  first 
described  by  Recklinghausen,  under  the  name  of  Saftcan'dlchen. 
We  propose  to  call  it  lymphatic  canaliculi,  and  the  more  or 
less  branched  cells  contained  in  them,  lymphatic  cells. 

If  these  are  examined  in  a  island  of  tissue  surrounded  by 
lymphatic  capillaries,  it  is  seen  that  there  are  places  in  which 
the  cells  are  closer  together  and  less  branched  than  in  others, 
and  that  in  such  spots  they  are  often  arranged  in  linear  series, 
or  in  small  groups,  each  cell  being  marked  off  from  its  neigh- 
bors by  interstitial  lines,  so  that  they  resemble  an  endothelium. 
This  is  particularly  the  case  in  the  immediate  neighborhood  of 
the  lymphatic  capillaries ;  and  here  it  can  often  be  made  out 
that  cells  contained  in  canaliculi  are  in  contact  with  the  ele- 


128  LYMPHATIC    SYSTExM. 

ments  of  the  lymphatic  endothelium.  The  canalicular  cells  are 
also  in  communication  with  the  flat  cells  which  form  the  layer 
immediately  covered  by  the  serous  endothelium. 

The  anatomical  relation  of  the  canaliculi  and  lymph  cells  on 
the  abdominal  side  are  the  same  as  in  the  pleura.  To  demon- 
strate them,  the  abdominal  surface  of  the  centrum  tendineum 
is  prepared  in  the  same  way  as  last  described.  In  the  neigh- 
borhood of  the  large  vessels,  the  existence  of  a  similar  layer  of 
flat  elements  lying  underneath  the  serous  endothelium,  resem- 
bling in  character  those  already  described  in  the  pleura,  can  be 
demonstrated.  The  canaliculi  and  lymphatic  cells  of  the  pro- 
pria have  also  the  same  relation  to  each  other  and  to  the  super- 
ficial network  of  lymphatic  capillaries  as  in  the  pleura.  Finally, 
it  is  to  be  mentioned  that  in  the  tissue  which  occupies  the 
fascicular  channels  which  contain  no  lymphatics,  the  same 
character  can  be  observed.  Here  the  continuity  of  the  lym- 
phatic cells  with  the  similar  cells  of  the  tendon-tissue,  which, 
as  we  have  seen,  are  oblong  branched  placoids,  and  apply 
themselves  to  the  surfaces  of  the  primitive  bundles  of  fibrils, 
can  be  demonstrated. 

Pseudo-Stomata. — In  examining  carefully  the  pleural  sur- 
face of  a  diaphragm  which  has  been  treated  with  nitrate  of 
silver,  without  pencilling,  it  is  seen  that  there  are  here  and 
there  spaces  between  the  endothelial  elements  which  are  occu- 
pied by  bodies  of  a  more  or  less  branched  contour.  These  are 
usually  darker  in  color  than  the  endothelium  of  the  surface, 
and  often  exhibit  distinct  nuclei.  If  the  preparation  has  been 
partly  pencilled,  it  is  often  possible  to  observe,  at  the  junction 
of  the  pencilled  and  unpencilled  part,  that  the  bodies  in  ques- 
tion are  of  the  same  kind  with  the  flat  branched  cells  which 
are  covered  by  the  endothelium ;  and  it  can  be  also  made  out 
that  even  where  they  are  covered,  the  cells  of  this  layer  send 
up  projections  between  the  endothelial  cells  which  reach  the 
surface.  These  projecting  cells  may  be  called  pseudo-stomata. 
The  intimate  relation  which  exists  between  the  sub-endothelial 
cells  and  those  of  the  propria,  and  between  these  last  and  those 
which  line  the  lymphatic  vessels,  has  been  already  referred  to. 
That  these  cells  are  also  concerned  in  absorption  is  indicated 
by  the  fact  that,  in  chronic  inflammation,  and  other  conditions 
in  which  absorption  from  the  serous  surface  is  more  than  usually 
active,  these  pseudo-stomata  and  the  canaliculi  are  the  seat  of 
germination — and  that  if  coloring  matter  in  a  state  of  fine 
division  has  been  previously  introduced  into  the  peritoneum, 
they  are  found  to  contain  it. 

Lymphatic  System  of  the  Omentum  and  Mesen- 
tery.— To  demonstrate  the  lymphatic  structures  of  the  omen- 
tum, the  peritoneal  cavity  is  opened  in  a  rabbit  just  killed.  The 
large  and  small  intestines  having  been   pushed  aside  to  the 


BY    DR.    KLEIN.  129 

right,  the  omentum,  which  usually  lies  on  the  anterior  surface 
of  the  stomach,  is  carefully  brushed  in  situ,  from  below  up- 
wards, with  a  camel-hair  pencil,  moistened  with  peritonaeal 
liquid.  Half  per  cent,  solution  of  silver  is  then  allowed  to  drop 
over  the  surface  from  a  capillary  pipette,  until  the  membrane 
is  distinctly  turbid.  It  must  then  be  gently  streamed  with 
water,  and  removed  along  with  the  stomach,  and  placed  in 
water  exposed  to  the  light.  Portions  of  the  membrane  are 
then  cut  out,  and  covered  in  glycerin  with  the  pencilled  surface 
upwards.  In  preparations  so  obtained,  an  abundant  network  of 
lymphatics  presents  itself.  In  addition  to  this,  there  are  cer- 
tain parts  of  the  surface  in  which  the  lymphatic  cells  are 
crowded  together  in  patches.  It  is  seen,  in  parts  where  the 
endothelium  has  not  been  completely  removed,  that  the  cells 
which  lie  immediately  underneath  it  project  so  as  to  form 
pseudo-stomata,  and  in  other  respects  stand  in  the  same  rela- 
tion to  it  and  to  those  which  line  the  lymphatic  capillaries,  as 
on  the  surface  of  the  diaphragm.  It  is  also  seen  that  in  some 
of  the  patches  there  are  lymph  sinuses  which  communicate  with 
the  surface  by  true  stomata.  As  was  indicated  in  Chapter  II., 
the  endothelium  which  covers  these  lymphatic  patches,  particu- 
larly that  which  surrounds  stomata  and  pseudo-stomata,  differs 
from  that  of  the  general  surface,  by  the  smaller  size,  polyhedral 
form,  and  granular  appearance  of  the  elements.  The  same 
tissue  also  presents  itself  in  the  form  of  tracts  alongside  of  the 
larger  vessels. 

In  the  dog,  guinea-pig,  and  cat,  these  tracts  are  particularly 
well  developed  along  the  large  vessels  which  are  to  found  in 
the  trabecular  of  the  membrane.  Connected  with  these,  there 
are  nodular  structures  which  project  more  or  less  from  the 
surface.  Both  the  tracts  and  the  nodules  consist  of  aggrega- 
tions of  lymphatic  cells  close  together,  richly  supplied  with 
bloodvessels,  and  covered  with  an  endothelium  which  has  the 
same  characters  as  that  which  covers  the  patches.  In  the 
neighborhood  of  the  tracts,  lymphatic  vessels  are  usually'' to  be 
seen  on  one  or  both  sides,  which  often  communicate  by  cross 
branches,  and  stand  in  the  same  relation  to  the  lymphatic 
elements  as  in  the  patches.  The  canaliculi  of  the  tracts  and 
nodules  sometimes  contain  what  appear  to  be  young  cells, 
which,  from  what  has  been  observed  in  pathological  conditions 
of  the  structure,  must  be  regarded  even  in  the  normal  state  as 
to  a  great  extent  offsprings  of  the  endothelial  elements. 

Mesentery. — In  the  mesentery  treated  in  the  same  way  as 
that  above  described,  in  addition  to  the  lymphatic  vessels 
which  proceed  from  the  intestine,  numerous  lymphatics  with 
dilatations  (sinuses)  can  be  demonstrated.  The  canaliculi  with 
which  they  are  surrounded  and  in  communication,  pervades 
the  ground-substance  of  the  mesentery  in  every  direction.  In 
9 


130  LYMPHATIC    SYSTEM. 

the  cat  and  rabbit,  tho  endothelium  of  the  mesentery  exhibits 
pseudo-stomata  of  the  same  character  as  in  the  omentum.  In 
that  of  the  toad  and  common  frog,  the  trabecular,  in  which  the 
large  vessels  run,  split  into  a  kind  of  meshwork  of  smaller 
processes,  the  spaces  of  which  are  occupied  by  large  lymphatic 
sinuses,  in  which  a  beautiful  endothelium  with  sinuous  outlines 
can  be  demonstrated  by  the  silver  method. 

Injection  of  Lymphatic  Glands  and  of  Mucous 
Membranes. — For  the  injection  of  the  lymphatics  of  the 
lymphatic  glands,  and  of  the  mucous  membranes,  the  "  Einstich 
Methode"  (method  of  puncture)  of  Ludwig  is  the  best.  The 
liquids  used  are  either  half  per  cent,  silver  solution  or  Prussian 
blue.  The  animal  to  be  employed  must  be  perfectly  fresh.  A 
very  fine  glass  canula  is  used,  which  is  connected  either  with  a 
syringe  or  with  the  apparatus  described  in  the  last  chapter. 
The  method  consists  in  penetrating  any  tissue  in  which  there 
are  numerous  lymphatics  (e.  g.}  the  submucosa  of  the  mucous 
membranes,  the  cortical  substance  of  a  gland,  or  the  loose 
tissue  beneath  the  costal  pleura),  with  a  needle  to  a  sufficient 
distance.  The  needle  having  been  withdrawn,  the  canula  pre- 
viously filled  with  the  solution  to  be  injected  is  introduced  into 
its  track,  and  connected  with  the  apparatus  or  syringe  as  the 
case  may  be.  The  canula  having  been  seized  with  ordinary 
dissecting  forceps,  the  liquid  is  injected.  If  it  is  seen  that  the 
colored  liquid  is  not  contained  in  vessels  but  merely  occupies 
a  bulging  cavity  in  the  tissue,  the  injection  must  be  discon- 
tinued as  unsuccessful.  In  the  case  of  the  mesenteric  or  ingui- 
nal glands  of  small  animals,  I  succeeded  in  obtaining  good 
results  with  a  tube  drawn  out  at  one  end  to  a  very  fine  point, 
and  bent  near  the  point  at  right  angles.  This  tube  having  been 
filled  with  the  liquid,  was  injected  by  the  mouth.  In  the  rabbit, 
nothing  can  be  easier  than  to  insert  such  a  tube  into  one  of  the 
lymphatics  of  the  mesentery,  and  in  this  way  to  inject  the  gland 
to  which  it  leads. — Lymphatic  glands,  after  injection,  must  be 
placed  in  alcohol  and  used  for  the  preparation  of  sections. 

Structure  of  the  Lymphatic  Vessels. — The  structure 
of  lymphatic  vessels  may  be  further  advantageously  studied  in 
those  of  the  mesenteiy.  In  small  cats  or  rabbits,  it  is  easy  to 
prepare  the  parts  of  the  mesentery  in  which  there  ai*e  abundant 
lymphatic  vessels  leading  to  the  mesenteric  glands,  by  stretch- 
ing them  on  cork  and  treating  them  with  silver,  after  pencilling 
away  the  endothelium  of  the  peritonaeum  with  a  camel-hair 
pencil,  moistened  with  serum.  In  these  vessels,  it  is  possible 
to  demonstrate  the  existence  of  transverse  muscular  fibres. 

Structure  of  the  Lymphatic  Glands. — Mesenteric 
Glands. — The  best  glands  for  the  purpose  of  study  are  those  of 
the  calf,  ox,  or  cat.  Small  portions  can  be  placed  in  Midler's 
liquid,  or  in  solution  of  bichromate  of  potash.     After  a  few 


BY    DR.    KLEIN.  131 

days,  it  is  possible  to  make  thin  sections  of  small  extent.  It  is 
easier,  however,  to  make  sections  of  glands  which  have  been 
steeped  two  or  three  days  in  common  alcohol.  The  sections, 
stained  or  unstained,  are  placed  two  or  three  together  in  a  test 
tube,  half  full  of  water,  which  must  then  be  shaken  regularly 
but  briskl}-  until  the  sections  acquire  the  characters  of  reticu- 
lated membranes.  The  contents  of  the  test  tube  are  poured 
into  a  shallow  capsule,  and  prepared  in  the  usual  manner, 
either  for  mounting  in  Dammar  varnish  or  glycerin.  It  is  well 
not  to  continue  the  agitation  longer  than  is  necessary  to  get 
rid  of  the  medullary  substance  of  the  gland.  The  globular  or 
ovoid  follicles  which  constitute  the  mass  of  the  cortical  sub- 
stance, and  are  in  continuity  with  the  lymphatic  cylinders,  are 
seen  in  such  preparations  to  have  the  following  structure  : — 
Each  consists  of  a  close  network  of  fibres,  the  meshes  of  which 
are  of  nearly  equal  size.  It  is  further  seen  that  the  fibres  are 
thickened  at  the  nodes,  and  that  each  thickening  contains  a 
nucleus.  The  younger  the  animal,  the  more  obvious  it  is  that 
the  network  consists  of  branched  cells.  The  follicle  also  con- 
tains numerous  capillaries.  From  the  network  of  branched 
cells  which  forms  the  adventitia  of  each  capillar}',  spring  fila- 
ments which  either  stretch  to  neighboring  capillaries,  or  form 
a  part  of  the  general  adenoid  network  of  the  follicles.  These 
filaments  are  alwa3rs  broader  at  their  bases  than  elsewhere, 
and  have  thickenings  which  contain  nuclei.  In  sections  which 
have  not  been  agitated,  the  whole  network  is  filled  with  small 
roundish  bodies  (so-called  lymph  corpuscles).  It  can  be  readily 
shown  in  glands  which  are  injected  from  the  lymphatics,  that 
each  follicle  is  surrounded  by  sinuses,  which  are  mere  dilata- 
tions of  the  different  lymphatic  vessels  of  the  cortex,  and  are 
in  like  manner  lined  with  endothelium,  as  is  seen  in  glands  in- 
jected with  nitrate  of  silver.  Outside  of  the  follicles  is  a  layer 
of  connective  tissue  which  contains  numerous  bloodvessels,  and 
is  continuous  towards  the  hilus,  with  the  trabecular,  which  form 
the  framework  of  the  organ.  Outwards  it  is  intimately  united 
with  the  capsule.  In  glands  of  which  the  bloodvessels  are  in- 
jected, capillary  loops  can  be  seen  to  penetrate  into  the  follicles 
from  the  rich  network  of  bloodvessels  with  which  each  is  in- 
vested. The  part  of  the  gland  between  the  cortical  substance 
and  the  hilus  consists  of  lymphatic  cylinders,  and  intervening 
trabeculse.  The  former  are  united  with  each  other  so  as  to 
form  a  network,  and  have  the  same  intimate  structure  as  the 
follicles,  as  regards  the  adenoid  network,  the  cells  it  contains, 
and  the  capillaries.  In  general  they  possess  only  capillaries  ; 
occasionally,  however,  larger  vessels  enter  them.  The  trabe- 
cular consist  of  fine  fibres  which  run  mostly  parallel  to  each 
other;  they  are  connected  into  a  meshwork,  the  intervals  of 
which  are  occupied  by  the  network  of  cylinders.     There  are, 


132  LYMPHATIC    SYSTEM. 

however,  between  the  outer  surfaces  of  the  cylinders  and  the 
trabecular,  spaces  to  which  we  shall  revert  immediately.  In 
sections  which  have  been  only  slightly  shaken,  it  is  possible  to 
observe  that  fibres  stretch  at  more  or  less  regular  intervals 
from  the  external  surface  of  the  cylinders  to  the  trabecular,  by 
which  the  intervening  space  is  divided  into  sections.  These 
fibres  appear  to  be  offsets  from  the  trabecular,  and  exhibit 
either  swellings  containing  nuclei,  or  distinct  nucleated  stellate 
cells.  In  sections  which  have  not  been  shaken,  the  whole  me- 
dullaiy  substance  appears  to  be  uniformly  full  of  lymph  cor- 
puscles. In  the  spaces,  as  we  have  seen,  they  can  be  shaken  out 
so  readily,  that  it  is  evident  they  lie  quite  loosely  ;  whereas,  in 
the  cylinders  themselves,  they  are  intimately  united  to  the  net- 
work. The  significance  of  this  structural  difference  can  be 
demonstrated  in  glands  in  which  the  different  lymphatics  have 
been  injected,  or,  still  better,  in  glands  which  have  been  injected 
by  the  puncture  method  with  nitrate  of  silver.  In  the  former 
case  it  is  possible  to  trace  the  injection  from  the  different  ves- 
sels of  the  cortex,  through  the  lymph  sinuses  which  surround 
the  follicles,  to  the  spaces  which  separate  the  cylinders  from 
the  trabecular,  and  thence  to  the  different  vessels  at  the  hilus. 
In  the  latter  case,  lymphatic  sinuses  are  met  with  in  the  me- 
dullary substance  near  the  hilus,  lined  with  endothelium,  which 
are  continuous  with  the  spaces  surrounding  the  cylinders  in 
such  a  way  that  their  endothelium  can  be  distinctly  traced  on 
to  the  surface  of  the  trabecular. 

Solitary  and  Agminated  Follicles  of  the  Intestine. — Folli- 
cles such  as  we  have  just  described  in  the  cortical  substance 
of  the  lymphatic  glands  occur  in  the  large  intestine  as  solitary 
follicular  bodies,  or  in  the  small  intestine,  in  groups  (the  so- 
called  Peyer's  patches.  See  p.  125). 

Thymus  Gland. — This  is  to  be  regarded  merely  as  an 
aggregation  of  follicles  of  the  same  kind.  Neither  in  their 
structural  elements,  nor  in  the  relation  of  these  to  the  vessels 
or  lymphatics,  can  any  difference  be  made  out.  In  man,  as 
well  as  in  the  dog,  the  external  surface  of  the  capsules  is 
covered  with  an  endothelium  identical  with  that  of  the  pleura. 
The  tonsils  and  follicular  glands  at  the  base  of  the  tongue  are 
almost  made  up  of  aggregations  of  lymphatic  follicles. 


BY    DR.    KLEIN.  133 


CHAPTER  IX. 

ORGANS  OF  RESPIRATION. 

The  structure  of  the  larynx,  trachea,  and  bronchi  can  be 
completely  studied  in  sections  of  organs  hardened  in  chromic 
acid.  The  epithelium  has  been  already  fully  described  else- 
where. An  animal  having  just  been  killed,  the  tubes  are 
opened,  washed  with  very  dilute  solution  of  bichromate  of 
potash,  and  placed  in  the  hardening  liquid.  In  thin  sections, 
the  relations  of  the  mucosa  submucosa  with  its  glands,  carti- 
lages, perichondrium,  muscular  fibres,  and  ganglia,  may  be 
completeby  made  out.  The  bloodvessels  may  be  injected  in  the 
ordinary  way,  and  the  lymphatics  by  puncture  of  the  submu- 
cosa. The  network  of  elastic  fibres  which  surround  the  alveoli 
are  most  readily  studied  in  thin  sections  of  fresh-frozen  lungs 
of  small  mammalia.  The  sections  are  steeped  in  acidulated 
water  till  the  air-bubbles  have  escaped,  and  then  spread  out 
on  an  object-glass  and  covered  in  glycerin.  The  structure  of 
the  fine  bronchi  ma}7  be  well  studied  as  regards  its  epithelium, 
minute  glands,  muscular  coat,  and  innumerable  large  gangli- 
onic masses,  in  sections  of  lungs  of  human  foetuses  of  the 
last  months  of  pregnane}',  which  have  been  hardened  in  one- 
tenth  or  one-eighth  per  cent,  solution  of  chromic  acid.  The 
flat  epithelial  elements  of  the  alveoli,  as  well  as  those  which 
line  the  finest  bronchial  tubes,  can  be  best  examined  in  lungs 
of  small  mammalia,  prepared  by  placing  a  canula  in  the 
trachea,  removing  the  sternum,  and  then  injecting  the  bronchi 
with  one-tenth  to  one-eighth  percent,  solution  of  chromic  acid, 
until  the  organ  is  moderately  distended.  The  trachea  is  then 
tied,  and  the  lungs  are  carefully  removed  from  the  thorax 
along  with  the  heart,  after  separating  them  first  from  the 
spinal  column,  and  then  from  the  diaphragm;  the  whole  is 
then  placed  in  liquid  of  the  same  strength.  Another  method, 
which,  however,  does  not  answer  so  well,  is  that  of  injecting 
half  per  cent,  solution  of  silver  into  the  pulmonary  artery. 
Good  injected  preparations  of  lungs  can  be  obtained  by  filling 
the  air-passages  with  cacao  butter,  and  the  bloodvessels  with 
gelatin-mass,  simultaneously.  A  rabbit  is  killed  by  opening 
the  crural  artery.  The  trachea  having  been  prepared,  a  canula 
fitted  to  a  nozzle  is  fixed  in  it.  The  sternum  is  then  removed, 
and  a  second  canula  inserted  in  the  pulmonary  artery  close  to 


134  ORGANS   OF   RESPIRATION. 

its  origin.  As  much  air  as  possible  is  now  pumped  with  a 
syringe  out  of  the  trachea,  and  the  stop-cock  closed.  The 
apparatus  for  injection  having  been  previously  put  in  readi- 
ness, all  must  be  connected,  and  the  pressure  raised  in  the  tube 
to  the  required  point,  i.  e.,  sixty  to  eighty  millimetres,  so  that 
at  an}-  moment  the  stop-cock  of  the  nozzle  may  be  opened  and 
the  injection  begun.  A  sufficient  quantity  of  cacao  butter 
having  been  fused  in  a  capsule,  a  middle-sized  syringe  is  filled 
with  the  hot  liquid,  and  fitted  into  the  nozzle,  which  is  inserted 
into  the  trachea,  and  the  injection  begun.  The  moment  that 
the  cacao  butter  has  begun  to  enter,  an  assistant  opens  the 
stop-cock1  of  the  canula  in  the  pulmonary  artery.  As  soon  as 
the  lung  appears  to  be  distended  with  the  butter,  the  stop-cock 
of  the  trachea  is  closed,  but  the  injection  of  the  bloodvessels 
is  continued.  As  soon  as  this  appears  to  be  complete,  the  left 
auricle  of  the  heart  is  comprised  in  a  ligature,  by  tightening 
which  the  pulmonar}'  veins  are  completely  closed.  A  few 
moments  later,  the  stop-cock  in  the  artery  is  also  closed,  and 
the  animal  placed  in  a  basin  so  that  the  thoracic  organs  are 
immersed  in  cold  water.  As  soon  as  the  lungs  are  seen  to  be 
firm,  they  are  taken  out  with  the  trachea  and  placed  in  common 
alcohol.  In  two  or  three  days,  small  portions  may  be  cut  out 
and  placed  for  a  short  time  in  absolute  alcohol,  and  then 
embedded  for  the  preparation  of  sections.  The  sections  must 
be  steeped  in  oil  of  turpentine  or  cloves,  till  the  cacao  butter 
is  dissolved  out ;  this  may  be  ascertained  by  placing  the  watch- 
glass  containing  them  under  a  low  power.  Turpentine  accom- 
plishes this  more  quickly  than  oil  of  cloves.  The  sections 
must  be  mounted  in  Dammar  varnish.  The  relation  between 
the  different  bloodvessels  and  the  capillary  network  of  the 
walls  of  the  alveoli,  are  admirably  seen  in  such  preparations. 
If  it  is  intended  to  preserve  the  structure  of  the  pulmonary 
tissue  unimpaired  and  at  the  same  time  to  inject  the  blood- 
vessels, half  per  cent,  solution  of  salt  or  of  bichromate  of 
potash  may  be  substituted  for  the  cacao  butter,  and  two  per 
cent,  solution  of  Prussian  blue  for  the  gelatin  mass.  The 
organ  must  be  placed  in  alcohol  as  before. 

1  Great  care  must  be  taken  to  keep  the  tube  leading  from  the  bottle 
containing  the  mass,  as  well  as  the  nozzle,  warm  with  hot  sponges, 
otherwise  there  will  be  great  danger  of  the  solidification  of  the  gelatin 
in  those  parts,  during  the  time  which  intervenes  between  the  prepara- 
tion of  the  apparatus  and  the  commencement  of  the  injection. 


BY    DR.    KLEIN.  135 


CHAPTER  X. 
ORGANS  OF  DIGESTION. 

Teeth. — Polished  sections  of  teeth  are  prepared  in  the 
same  way  as  those  of  bone.  They  must  be  made  in  various 
directions.  For  the  study  of  the  development  of  the  teeth, 
maxillary  bones  of  human  foetuses,  softened  in  chromic  acid 
in  the  way  previously  directed,  must  be  used.  The  reader  is 
referred  for  the  description  of  the  structure  to  the  ordinary 
handbooks  of  general  anatomy. 

Salivary  Glands  and  Pancreas. — These  organs  must 
be  steeped  several  da}rs  in  half  per  cent,  solution  of  bichro- 
mate of  potash  and  prepared  b}r  teasing.  Small  bits  of  the 
fresh  glands  may  be  steeped  for  fort}^-eight  hours  in  the  dark, 
in  one-tenth  to  one-half  per  cent,  solution  of  osmic  acid,  and 
then  either  placed  in  water  for  a  day  or  two,  with  a  view  to 
preparation  by  teasing,  or  hardened  in  alcohol  for  the  prepara- 
tion of  sections.  In  either  case  the  preparations,  if  kept, 
must  be  placed  in  concentrated  solution  of  acetate  of  potash. 
The  arrangement  of  the  alveoli  and  their  ducts,  and  the 
characters  of  the  epithelium  of  each,  can  be  best  seen  in 
sections  of  glands  hardened  in  alcohol,  and  stained  with 
dilute  carmine.  In  such  sections,  the  beautiful  mosaic  of  the 
pol\rhedral  epithelial  cells  of  the  alveoli,  each  consisting  of 
granular  protoplasm,  forms  a  striking  contrast  to  the  cylindri- 
cal epithelial  lining  of  the  ducts;  the  latter  consisting  of  pale 
slender  cells,  each  of  which  appears  streaked  in  the  direction 
of  its  length,  and  contains  an  oblong  nucleus  in  its  outer  third. 
The  alveoli  are  united  into  groups  (lobules)  by  delicate 
bundles  of  connective  tissue.  In  teased  preparations,  the 
cellular  and  fibrous  elements  of  the  connective  tissue,  and  the 
ganglion  cells  which  are  met  with  here  and  there,  can  be  studied. 
In  injected  glands,  each  alveolus  is  seen  to  be  invested  by  a 
delicate  and  very  abundant  network  of  capillaries. 

Mucous  Membrane  of  Mouth,  Tongue,  Pharynx, 
and  (Esophagus. — The  structure  of  these  mucous  mem- 
branes can  be  well  seen  in  sections  of  organs  hardened  in 
chromic  acid.1  For  studying  the  epithelium,  the  papilla,  the 
glands,  and   muscles,  this  mode  of  preparation  is  sufficient. 

1  As  regards  the  tongue,  see  also  the  chapter  on  Organs  of  Special 
Souse. 


136  ORGANS    CF   DIGESTION. 

The  lymphatic  vessels,  e.  g.,  in  the  pharynx  and  at  the  root  of 
the  tongue,  can  be  filled  by  the  puncture  method,  after  which 
the  injected  parts  must  be  hardened  in  alcohol,  and  used  for 
the  preparation  of  sections.  To  see  the  loops  of  fine  capil- 
laries in  the  papilla  of  the  mouth,  tongue,  and  pharynx,  these 
parts  must  be  injected.  As  regards  the  distribution  of  the 
fine  nerves,  see  Chapter  V. 

Stomach. — The  relation  of  the  muscularis  mucosae,  the 
submucous  tissue,  the  musculosa  and  the  ganglia  to  each 
other,  can  be  well  shown  in  sections  of  organs  hardened  in 
chromic  acid.  For  the  study  of  the  glands,  the  best  method 
is  to  open  the  stomach  of  the  cat  or  dog  immediately  after 
death,  carefully  inverting  it  so  as  to  empty  it  of  its  contents, 
and  then  to  stream  it  gently  with  water.  Thin  folds  of  the 
membrane  must  be  snipped  off  with  sharp  curved  scissors  and 
placed  in  common  alcohol.  After  three  or  five  days  the  ob- 
jects are  ready  for  the  preparation  of  sections,  the  direction  of 
which  must  be  parallel  or  vertical.  The  parallel  sections  must 
be  made  at  various  depths.  For  the  coloring  of  these  sections 
a  staining  liquid  prepared  after  Beale's  formula  (omitting  the 
alcohol)  answers  well ;  but  it  is  necessary  to  free  it  from  excess 
of  ammonia,  either  by  careful  neutralization  with  acetic  acid 
or  by  warming  it  in  the  water-bath.  The  sections  having  been 
placed  in  this  liquid  in  a  watch-glass,  it  is  put  in  a  closed  ves- 
sel along  with  a  second  wratch-glass  containing  water  with  a 
trace  of  ammonia.  After  twenty-four  hours  the  sections  are 
removed,  washed  in  dilute  glycerin,  and  transferred  to  con- 
centrated glycerin  in  another  watch-glass,  which  is  then  placed 
in  the  closed  vessel  along  with  a  glass  containing  common 
acetic  acid.  After  twenty-four  to  twenty-eight  hours  the 
sections  may  be  finally  covered  in  glycerin.  In  such  prepara- 
tions the  gland  tubes  of  the  fundus  (the  so-called  peptic 
glands),  with  their  two  kinds  of  epithelium,  are  well  seen. 
Next  the  cavity  of  the  gland  it  consists  of  C3Tlindrical  cells 
(the  Hauptzellen  of  Heidenhain),  which  are  scarcely  colored 
by  the  carmine,  and  are  very  finely  granular.  The  nuclei  of 
these  cells  are  occasionally  colored,  but  usually  not  so.  Un- 
derneath them,  i.  e.,  next  the  membrana  propria,  both  in 
vertical  and  parallel  sections,  ovoid  granular  cells  are  seen 
which  are  strongly  stained.  These  last  (the  Belegzellen  of 
Heidenhain)  do  not  form  a  continuous  layer  in  either  direc- 
tion :  they  occur  in  small  numbers  in  the  half  or  two-thirds  of 
the  gland  next  the  muscularis  mucosae,  i.  e.,  in  the  body  of  the 
gland — more  abundantly  in  the  adjoining  part,  which  is 
usually  called  the  neck,  where  thej'  more  or  less  conceal  the 
cylindrical  layer.  The  short  duct,  in  which  usually  two 
tubes  open,  possesses  an  epithelium  of  the  same  kind  as  that 


BY    DR.    KLEIN.  137 

which    covers   the   surface,  consisting  of  slender  cylindrical 
elements. 

When  these  structures  are  compared  as  seen  in  fed  animals 
and  in  animals  in  inanition,  it  is  found  that  in  the  former  the 
staining  extends  both  to  the  ovoid  cells  and  to  the  columnar 
cells.  A  difference  of  the  same  kind  may  be  shown  in  similar 
sections  stained  with  anilin.  An  extremely  dilute  aqueous 
solution  is  used.  The  sections  must  be  placed  in  a  watch- 
glass  containing  the  liquid,  which  is  allowed  to  stand  twenty- 
four  hours  in  a  closed  vessel,  the  air  of  which  is  kept  saturated 
with  moisture.  The  preparations  can  then  be  at  once  inclosed 
in  glycerin.  The  only  difference  between  the  results  of  the 
two  methods  is,  that  the  cylindrical  cells  are  here  slightly 
tinged  even  in  inanition.  The  convoluted  and  much-branched 
tubes  which  occur  in  the  region  of  the  pylorus  contain  only 
cylindrical  cells,  which  correspond  to  those  of  the  same  form 
in  the  proper  peptic  glands.  Between  these  last  and  the 
branched  glands,  intermediate  forms  are  met  with,  which 
differ  from  each  other  in  the  number  of  ovoid  cells  (Belegzel- 
len)  which  they  contain,  the  number  diminishing  according 
to  the  distance  from  the  pylorus. 

The  processes  of  the  muscularis  mucosae,  which  stretch 
towards  the  surface  through  the  mucosa  between  the  glands, 
can  be  better  seen  in  chromic  acid  preparations. 

Small  Intestine. — The  characters  of  the  epithelium  of  the 
small  intestine  in  the  fresh  state  have  been  already  described. 
They  may  be  further  advantageously  studied  in  sections  of 
hardened  organs,  which  will  also  serve  for  the  demonstration 
of  the  following  structures — the  dense  reticulum  of  the  sub- 
stance of  the  villi,  with  the  round  cells  in  its  interspaces ;  the 
anatomical  relations  of  the  single  or  double  central  lymphatic 
vessel  which  each  villus  contains ;  the  slender  bundles  of 
longitudinal  unstriped  muscular  fibres  which  run  out  around 
the  lymphatics  towards  the  apex  of  each  villus  ;  the  reticular 
tissue  of  the  mucosa,  identical  in  its  characters  with  that  of 
the  villi,  in  which  the  tubes  of  Lieberkuhn  are  sunk ;  the  mus- 
cularis mucosae,  with  the  distinct  layers  of  which  in  many 
parts  it  is  seen  to  consist,  and  the  bundles  of  fibres  which  ex- 
tend from  it,  either  towards  the  villi  or  between  the  glands ; 
and,  lastly,  the  submucosa  and  muscularis  externa.  The  in- 
testine should  be  treated  as  follows :  The  intestine  of  a  cat, 
dog,  rabbit,  rat,  or  hedgehog  just  killed  is  opened,  small  por- 
tions are  at  once  placed  in  water  colored  with  bichromate  of 
potash,  and  washed.  They  are  then  transferred  to  a  one-tenth 
or  one-eighth  per  cent,  solution  of  chromic  acid,  and  five  or 
six  days  later  to  dilute  alcohol,  in  which  they  are  steeped  for 
some  days.  Thereupon  small  portions  are  embedded  in  gum, 
and  colored  and  mounted  as  directed  in  Chapter  VI. 


138  ORGANS   OF    DIGESTION. 

The  Glands  of  Brunner. — These  glands  may  be  studied 
in  thin  vertical  sections  of  the  duodenum  of  the  cat  or  dog. 
They  lie  in  the  submucosa,  and  consist  of  branched  tubes, 
which  are  much  convoluted  and  are  lined  throughout  with 
cylindrical  epithelium.  Towards'the  muscula?*is  externa  they 
are  invested  by  a  special  layer  of  unstriped  muscular  fibres, 
originating  from  the  muscularis  mucosae.  The  ducts  of  these 
glands,  after  penetrating  the  muscularis  mucosae,  diminish  in 
calibre  as  they  pass  outwards  towards  the  surface  between  the 
Lieberkuhn's  tubes.  The  epithelium  with  which  they  are  lined 
exhibits  a  striking  contrast  to  that  of  the  tubes,  the  elements 
being  slenderer  and  much  more  readily  stained  with  carmine. 

Peyer's  Follicles. — The  best  preparations  are  to  be  ob- 
tained from  the  lower  end  of  the  ileum  of  the  dog  or  cat.  The 
intestine  of  the  rabbit  may  also  be  used.  Thin  sections  of 
these  parts  may  be  prepared  as  above  directed,  with  the  excep- 
tion that  the  time  occupied  in  each  stage  of  the  process  of 
hardening  may  be  shortened.  The  hardened  portions  must, 
moreover,  be  embedded  in  wax-mass  rather  than  in  gum.  The 
sections,  whether  stained  or  not,  should  be  steeped  for  twent}-- 
four  hours  in  water,  and  then  shaken  in  the  manner  recom- 
mended for  the  preparation  of  sections  of  the  lymphatic 
glands.  They  are  finally  mounted  in  glycerin.  In  this  way 
the  recticular  tissue  both  of  the  mucosa  and  of  the  follicle  is 
well  shown.  From  sections  of  Peyer's  patches,  prepared  in 
the  manner  previously  described,  we  learn  that  each  follicle  is 
surrounded  by  a  large  lymphatic  sinus — that  each  is  deeply 
embedded  in  the  submucosa,  sometimes  approaching  the  mus- 
cularis externa — that  a  small  part  of  each  penetrates  the  mus- 
cula?-is  mucosae  and  projects  into  the  mucosa,  some  of  the 
summits  losing  themselves  in  its  tissue  without  any  defined 
limit,  others  reaching  up  to  the  epithelium.  When  this  is  the 
case,  the  epithelial  elements  are  smaller,  and  consist  of  several 
layers  of  polyhedral  cells.  Both  in  situations  where  there  are 
distinct  patches,  and  in  those  regions  in  which  (as  occurs  in  the 
ileum  of  the  cat  and  dog)  the  whole  of  the  submucosa  is  occu- 
pied with  follicles,  the  individual  follicles  are  in  continuity  at 
their  widest  part.  The  network  of  lymphatic  vessels  of  the 
submucosa,  with  which  the  sinuses  of  the  follicles,  as  well  as 
the  tymphatics  of  the  villi,  are  in  immediate  communication, 
can  be  readily  filled  with  soluble  Prussian  blue,  by  the  method 
of  puncture.  It  is  most  easilj-  accomplished  in  large  rabbits. 
Half  per  cent,  silver  solution  may  be  also  used  for  the  demon- 
stration of  the  endothelial  lining  which  all  these  vessels  pos- 
sess. 

To  prove  that  in  the  absorption  of  fat  the  network  of  the 
stroma  of  the  villi  is  concerned,  a  rat,  hedgehog,  or  kitten  is 
allowed  to  remain  without  food  for  a  day  or  two,  and  then  fed 


BY    DR.    KLEIN.  139 

with  milk  (rat,  kitten)  or  fat  meat  (hedgehog),  and  killed  a  few 
hours  afterwards  by  strangulation.  The  belly  having  been 
opened,  those  parts  which  to  the  naked  eye  appear  best  filled 
are  ligatured  without  delay,  and  placed  at  once  (without  open- 
ing them)  into  Midler's  liquid,  previously  slightly  warmed. 
After  a  few  days,  small  portions  are  cut  out  and  immersed  in 
half  per  cent,  solution  of  osmic  acid,  and  then,  twenty-four 
hours  later,  replaced  in  Midler's  liquid,  or  in  one-tenth  per 
cent,  chromic  acid  solution.  Bits  of  the  intestine  so  prepared 
must  finally  be  embedded  in  gum-mass  for  the  preparation  of 
sections,  which  must  be  mounted  in  acetate  of  potash.  In 
sections  which  comprise  villi,  the  epithelium,  and  the  reticulum 
and  central  lymphatic  vessel  of  each  villus  are  observed  to  be 
filled  with  fat  drops  stained  brown  or  black  by  the  reagent. 
When  a  villus  is  cut  transverseby,  it  is  seen  that  trabecular 
beset  with  blackish  or  dark-brown  fat  drops,  arranged  in  a 
reticulate  manner,  radiate  from  the  central  lymphatic  outwards 
to  the  epithelium. 

Bloodvessels. — The  arrangement  of  the  capillary  networks 
which  surround  the  glands,  and  those  of  the  villi,  must  be 
studied  in  injected  preparations. 

Nerves. — Meissner's  and  Auerbach's  ganglia  have  been 
already  referred  to  sufficiently  in  Chapter  V. 

Large  Intestine. — The  methods  for  studying  the  epithe- 
lium, the  Lieberkuhnian  tubes,  and  the  solitary  follicles  of  the 
submucosa,  the  mucosa  and  muscular  structures,  are  the  same 
as  those  used  for  the  small  intestine.  The  agminate  follicles, 
with  their  lymphatic  sinuses,  may  be  particularly  well  seen  in 
the  vermiform  appendix  of  the  rabbit.  The  muscularis  and 
glands  of  the  mucosa  are  best  seen  in  the  wart-like  prominences 
of  the  colon.  Good  examples  of  the  Lieberkuhnian  tubes,  the 
muscularis  mucosae,  and  the  solitaiy  follicles,  are  to  be  obtained 
from  the  dog.  The  ganglia  of  Meissner  are  well  seen  in  the 
dog  and  cat,  and  in  the  human  foetus. 

Liver. — For  the  study  of  the  liver,  fine  sections  of  the  fresh 
organ  may  be  employed.  By  teasing  these  out  with  needles, 
the  characters  of  the  elements  of  the  connective  tissue,  and 
the  form  of  the  liver-cells  and  their  nuclei,  can  be  satisfactorily 
made  out.  The  arrangement  of  the  cells  in  the  acini  can  be 
demonstrated  in  sections  of  liver  of  human  foetus,  or  of  the 
smaller  domestic  animals,  hardened  in  solution  of  bichromate 
of  potash  or  very  dilute  solution  of  chromic  acid.  The  best 
plan  is  to  steep  very  small  portions  of  liver  for  four  or  five 
days  in  a  large  quantity  of  one  to  two  per  cent,  solution  of 
bichromate  of  potash,  and  then  for  twenty-four  to  forty -eight 
hours  in  common  alcohol.  The  sections  so  obtained  are 
stained  in  the  usual  way  in  carmine.  In  such  preparations 
the  beautiful  regular  groups  or  oblong  tracts  of  liver-cells, 


140  ORGANS    OF    DIGESTION. 

with  the  capillaries  which  separate  them  from  each  other,  are 
well  seen.  Here  and  there  it  is  observed  that  an  interstitial 
hole  or  orifice  appears  to  be  formed  by  the  apposition  of  two 
semi-circular  notches  in  the  border  of  contiguous  cells,  or.  in 
other  cases,  bv  three  cells  similarly  notched.  By  comparing 
these  appearances  with  sections  of  organs  in  which  the  ulti- 
mate bile  ducts  are  injected,  it  is  seen  that  the  orifices  cor- 
respond to  sections  of  these  channels.  They  possess  no  special 
wall,  being  apparently  bounded  immediately  by  the  cell-sub- 
stance. In  such  preparations  the  cylindrical  epithelium  of  the 
interlobular  ducts  can  also  be  well  seen.  The  bloodvessels 
should  be  studied  in  organs  in  which  the  vena  portse  has  been 
previously  injected  with  gelatin  mass  ;  for  which  purpose  the 
liver  of  a  rabbit,  guinea-pig,  or  small  dog,  answers  best.  The 
animal  having  been  killed  by  bleeding,  a  canula  is  inserted  in 
the  vein,  and  a  ligature  placed  round  the  vena  cava,  in  the 
thorax.  Before  injecting  the  mass,  it  is  best  to  send  warm 
half  per  cent,  solution  of  salt  through  the  organ,  till  it  be- 
comes colorless.  Carmine-gelatin  or  Prussian-blue-gelatin  mass 
must  then  be  injected  in  the  manner  directed  in  Chapter  VI. 
Before  leaving  off,  the  ligature  on  the  cava  is  tightened,  after 
which  a  somewhat  stronger  impulse  is  given,  so  as  to  keep 
the  vessels  distended.  The  vena  portse  having  been  ligatured, 
the  organ  is  treated  as  before  directed.  In  such  preparations 
the  whole  course  of  the  vessels  from  the  interlobular  veins, 
through  the  capillary  s3-stem  of  each  acinus  to  the  intralobular 
vein,  may  be  studied.  If  it  is  desired  to  inject  the  hepatic 
artery  and  the  portal  system  with  different  colors,  this  may  be 
accomplished  by  securing  a  canula  at  the  same  time  in  both 
vessels ;  the  nozzle  of  the  one  canula  being  connected  with 
a  Woolff  s  bottle  containing  carmine  mass,  that  of  the  other 
with  a  similar  bottle  containing  Prussian  blue.  The  connect- 
ing tubes  leading  to  the  two  bottles  are  adapted,  one  to  each 
arm  of  a  T"  tube,  the  stem  of  which  is  in  communication  with 
the  pressure  apparatus,  so  that  the  same  pressure  is  exerted  at 
the  same  time  in  both  bottles.  The  bile  ducts  can  be  injected 
naturally  by  the  same  method  which  is  used  for  injecting  the 
urinary  tubes,  or  in  the  ordinary  way  by  the  hepatic  duct. 
After  ligaturing  the  cystic  duct,  two  per  cent,  solution  of  Prus- 
sian blue  can  be  injected  with  such  success  that  in  parts  the 
capillary  bile  ducts  are  filled.  The  livers  that  answer  best  for 
the  purpose  are  those  of  mature  foetuses,  puppies,  and  rabbits. 
As  soon  as  a  successful  injection  has  been  obtained  (as  may  be 
judged  of  by  inspection),  it  is  desirable  to  inject  the  portal 
system  with  a  different  color. 

The  Spleen. — For  the  study  of  the  elements  of  the  pulp  of 
the  spleen  it  is  absolutely  necessary  to  use  the  organs  of  ani- 
mals just  killed.     Preparations  may  be  made  either  by  scraping 


BY    DR.    KLEIN.  141 

the  sectional  surface,  or  by  teasing.  The  tissue  of  the  trabe- 
cular,the  special  sheaths  of  the  arteries,  the  stroma  of  the  pulp, 
and  that  of  the  Malpighian  corpuscles,  are  best  studied  as  fol- 
lows: Small  bits  of  fresh  spleen  are  steeped  in  one  or  two  per 
cent,  solution  of  bichromate  of  potash  till  they  are  fit  for 
making  sections.  The  thin  sections  are  then  washed  in  water 
(after  coloring  if  desired),  and  carefully  shaken  in  a  test  tube. 
They  are  then  covered  in  glycerin.  In  organs  successfully  in- 
jected and  prepared  in  the  usual  way,  it  can  be  made  out  that 
the  vascular  system  is  not  definitely  limited  as  in  other  tissues. 
The  circulating  blood,  before  reaching  the  veins  of  the  pulp, 
passes  through  a  system  of  channels  without  definite  walls, 
the  so-called  vasa  serosa. 


CHAPTER   XL 


SKIN,    CUTANEOUS   GLANDS,  AND    GENITO-URINARY 
APPARATUS. 

Section  I. — Skin. 

Methods  of  Study. — For  the  study  of  the  structure  of  the 
skin  in  general,  the  human  integument  is  preferable  to  that  of 
the  lower  animals.  Portions  of  skin  with  subcutaneous  cellu- 
lar tissue,  obtained  in  as  fresh  a  state  as  possible,  are  placed 
in  sherry -yellow  solution  of  chromic  acid,  containing  from  one- 
tenth  to  one-fourth  per  cent.  After  a  week,  or  even  sooner, 
they  should  be  transferred  to  common  alcohol,  and  used  for 
the  preparation  of  sections.  As  regards  examination  of  the 
epidermis,  it  is  only  necessary  to  add  to  the  directions  given 
in  Chapter  II.,  that  the  best  parts  of  the  skin  for  the  prepara- 
tion of  sections  are  the  volar  side  of  the  fingers,  the  lips,  the 
alae  of  the  nose,  and  the  eyelids.  Any  part  will  answer  equally 
well  for  the  investigation  of  the  structure  of  the  corium.  If 
it  is  desired  to  demonstrate  the  sweat  glands,  the  palm  of  the 
hand,  the  axilla,  and  after  these  the  forehead,  answer  best. 
Hairs  can  be  examined  in  the  skin  of  the  scalp,  the  upper  lip, 
and  eyelids.  The  sebaceous  glands,  whether  those  which  open 
into  hair  follicles,  or  those  of  which  the  orifices  are  free,  can 
be  best  prepared  in  the  labia  majora,  prepuce,  scrotum,  or  in- 
ternal lining  of  the  orifice  of  the  nose  or  eyelid  of  new-born 
children,  and  in  the  scalp  of  adults.  The  unstriped  muscular 
fibres  of  the  skin,  particularly  the  hairs,  can  be  studied  in  the 
scalp  and  scrotum,  or  in  the  skin  which  covers  the  anterior 


142  SKIN. 

and  external  aspect  of  the  thigh.  The  bloodvessels  can  be 
best  studied  in  injected  preparations,  for  which  purpose  the 
best  way  is  to  inject  one  of  the  upper  extremities  of  a  new- 
born foetus. 

The  lymph  vessels  can  be  made  out  most  easiby  in  oedenia- 
tous  skin.  The  integument  must  be  removed  with  the  whole 
of  the  subcutaneous  tissue,  and  then  sacrificed  at  one  or  two 
points,  and  left  twenty-four  hours  suspended,  until  much  of 
the  liquid  has  drained  awa}\  The  vessels  can  then  be  injected 
by  the  puncture-method. 

The  preparation  of  the  nerves  and  cellular  elements  of  the 
corium  and  papillae  by  the  gold  method  has  been  already  de- 
cribed.  The  Pacinian  corpuscles  and  tactile  corpuscles  of 
Meissner  can  be  advantageously  seen  in  thin  sections  of  the 
volar  side  of  the  finger  or  palm,  after  hardening  in  chromic 
acid. 

Sweat  Glands. — The  sweat  glands  are  of  two  forms. 
Those  of  the  first  form  are  long  and  slender  tubes  closed  at 
one  end.  The  secreting  part,  or  body  of  the  gland,  is  convo- 
luted, and  is  imbedded  in  the  subcutaneous  tissue  at  a  variable 
depth;  the  duct  which  passes  through  the  corium  to  the  sur- 
face follows  a  slightly  winding  course.  The  gland,  whether 
seen  in  transverse  or  longitudinal  sections,  is  found  to  be 
limited  by  a  fine  membrane  (membrana  propria)  lined  by  a 
single  layer  of  cylindrical  epithelium,  the  free  surface  of  which 
forms  the  internal  surface  of  the  gland.  In  very  thin  sections, 
in  which  it  is  possible  to  compare  the  epithelium  of  the  ducts 
with  that  of  the  bod}r  of  the  gland,  it  is  seen  that  the  elements 
of  the  former  are  more  slender.  In  the  duct  it  is  further  note- 
worthy that  the  nucleus  of  each  element  is  in  its  outer  third, 
and  that  the  nuclei  are  regularly  arranged.  In  the  elements 
of  the  body  of  the  gland  they  lie  in  the  middle  of  each  cell. 
In  the  epidermis,  the  duct  is  continued  towards  the  surface  as 
a  canal,  which  winds  spirally,  like  a  corkscrew.  This  is  par- 
ticularly the  case  when  the  epidermis  is  of  some  thickness. 

In  a  section  which  shows  the  whole  course  of  the  canal,  it 
is  seen  that  the  membrana  propria  becomes  continuous  with 
the  most  superficial  layer  of  the  corium,  while  the  epithelium 
of  the  duct  becomes  identified  with  the  elements  of  the  rete 
Malpighii.  This  first  form  of  sweat  glands  is  met  with  over 
the  whole  integument.  The  glands  of  the  second  form  occur 
along  with  the  others  in  grown  persons  onl}r,  and  are  subject 
to  great  differences  as  regard  their  distribution.  They  are 
always  to  be  found  in  the  skin  of  the  palm  of  the  hand,  of  the 
axilla,  and  of  the  scalp.  They  are  met  with  in  some  persons 
in  other  parts  of  the  body.  They  are  distinguished  from  the 
common  form  by  the  facts  that  they  are  three  or  four  times 
as  large,  that  the  tube  is  as  much  wider,  and  that  the  epithelium 


BY    DR.    KLEIN.  143 

consists  of  larger  elements,  which  are  coarsely  granular,  and 
of  polyhedral  form,  and  occasionally  contain  yellowish-brown 
pigment. 

As  the  epithelium  elements  are  often  found  separated  from 
the  membrana  propria,  it  may  be  inferred  that  the}'  are  much 
more  loosely  attached  to  it  than  in  the  other  form.  Further, 
it  is  to  be  noticed,  that  the  membrana  propria  contains  a  con- 
tinuous longitudinal  laj'er  of  unstriped  muscular  fibres,  which 
seem  to  lie  towards  its  inner  surface.  Wherever  glands  of  this 
form  occur,  they  appear  to  be  cpiiite  distinct  from  the  others, 
for  no  intermediate  or  transition  forms  present  themselves. 
It  is  possible  that  these  glands  have  a  casual  relation  to  the 
offensive  odor  of  perspiration  in  certain  persons. 

The  orifices  of  the  ducts  of  both  kinds  of  sweat  glands  are 
lined  with  laminated  epithelium,  which  is  in  direct  continuity 
with  the  rete  3falpighii.  The  cells  of  the  layer  which  lies  on 
the  propria  are  of  a  polyhedral  or  rather  pallisade  form. 
Those  which  lie  next  them  are  somewhat  flattened,  forming 
layers  which  are  more  and  more  scanty  the  further  the}'  are 
from  the  orifice  ;  they  entirely  cease  where  the  duct  joins  the 
gland.  The  membrana  propria  of  the  gland  itself  is  lined  by 
a  la}'er  of  polyhedral  cells,  which  are  of  uniform  size  and  ap- 
pearance, and  consist  of  protoplasm.  These  are  readily  stained 
by  carmine,  and  are  continuous  with  the  deepest  la}'er  of  the 
epithelium  (the  pallisade  cells). 

Sebaceous  Glands. — The  sebaceous  glands  consist  of  closed 
tubes,  which  are  usually  branched,  and  receive  a  variable  num- 
ber of  tributary  sacculi.  They  either  open  at  the  surface,  or 
into  hair  follicles.  In  every  sebaceous  gland  the  secreting  part 
may  be  distinguished  from  the  duct.  The  duct  is  lined  with 
pavement  epithelium,  which,  when  the  orifice  is  at  the  surface, 
can  be,  seen  to  be  continuous  with  the  rete  Malpighii.  In 
glands  which  open  into  hair  follicles,  it  is  continuous  with  the 
external  sheath  of  the  bulb.  In  passing  from  the  duct  to  the 
secreting  part,  the  epithelium  changes  its  character,  being  re- 
presented by  a  layer  of  granular,  cubical,  or  polyhedral  ele- 
ments which  lines  the  propria.  Besides  these  cells,  the  sacculi 
contain  larger  elements,  which  are  so  closely  packed  together 
as  to  be  flattened  against  each  other.  In  fresh  preparations 
these  appear  to  be  loaded  with  fat,  but  in  preparations  treated 
with  absolute  alcohol  and  oil  of  cloves  they  exhibit  a  distinct 
nucleus  and  investing  membrane.  The  sebaceous  glands  can 
be  best  studied  in  the  skin  of  mature  foetuses,  e.  g.,  in  that  of 
the  lips  and  nasal  orifice,  labia  majora,  prepuce,  and  scalp. 
The  acinous  form  is  exemplified  in  the  Meibomian  follicles  of  the 
eyelids.  Sections  of  these  parts  hardened  in  chromic  acid  must 
be  made,  which  can  be  stained  and  mounted  in  Dammar  var- 
nish. 


144  URINARY    APPARATUS. 

Hair. — With  reference  to  the  structure  of  hair,  it  is  of  im- 
portance to  notice  that  each  follicle  consists  of  a  connective 
tissue  layer,  and  of  a  layer  of  muscular  fibres.  The  former, 
which  is  richly  supplied  with  capillaries,  is  formed  of  fibres 
which  run  mostly  longitudinally,  and  seem  to  be  merely  a  con- 
densation of  the  surrounding  tissue.  In  certain  parts,  this 
layer  is  in  immediate  contact  with  the  external  hyaloid  mem- 
brane of  the  hair;  in  others,  there  exists  between  them  a  cir- 
cular layer  of  plain  muscular  fibres,  which  varies  in  distinct- 
ness in  different  varieties  of  hairs,  but  is  always  most  strongly 
developed  in  the  neighborhood  o'f  the  bulb.  In  the  eyelash  of 
the  mature  foetus,  the  muscular  la^'er  is  much  stronger  than 
the  connective  tissue  layer,  and  can  be  traced  over  the  whole  of 
the  bulb.  As  regards  the  structure  of  the  hair  itself,  all  that 
is  required  will  be  readily  understood  from  the  description 
given  in  the  ordinary  text-books. 

The  structural  facts  relating  to  the  root  of  the  hair  can  be 
easily  made  out  in  chromic  acid  preparations.  The  structure 
of  the  shaft  can  be  best  seen  by  preparing  fresh  hair  (of  the 
scalp)  in  concentrated  acetic  acid,  by  which  means  the  cuticle 
and  the  elements  of  the  medulla  are  brought  into  view.  For 
the  isolation  of  the  plates  of  the  cuticle,  and  of  the  fibre-cells 
of  the  substance  of  the  hair,  concentrated  sulphuric  acid  is 
used,  at  a  temperature  of  40°  to  50°  C,  in  which  the  hair  must 
be  heated  for  about  an  hour.  After  steeping  for  several  days 
in  two  per  cent,  solution  of  caustic  potash,  the  elements  of  the 
medulla  become  very  distinct.  The  development  of  the  hair, 
and  of  the  sweat  glands  and  sebaceous  glands,  may  be  studied 
in  embryos  at  various  periods,  in  preparations  hardened  with 
chromic  acid.  The  most  important  point  to  notice  is,  that  in 
mature  embryos,  or  even  in  the  eyelashes  of  children,  if  the 
section  coincides  precisely  with  the  axis  of  the  hair  and4nvolves 
the  papilla,  it  is  seen  that  that  part  of  the  external  hyaline  mem- 
brane which  extends  over  the  papilla  is  uninterrupted^  covered 
with  the  regularly  arranged  cells  of  the  external  sheath,  and 
that  these  cells  occup\r  the  whole  bulb  to  about  half-way  up 
the  root.  It  is  common  to  find  several  stages  of  development 
in  a  single  preparation,  from  which  it  can  be  learnt  that  the 
new  hair  takes  its  origin  from  the  axial  cells  of  the  sheath  of 
the  root,  being  formed  by  the  lengthening  of  these  elements. 

Section  II. — Urinary  Apparatus. 

Epithelium  of  the  Kidneys.— For  the  study  of  the  epi- 
thelium of  the  kidneys,  the  pig,  dog,  or  mature  foetus  may  be 
used.  The  fresh  kidneys  having  been  divided  into  two  halves, 
in  the  direction  of  the  length  of  the  organ,  juice  from  the  cut 
surface  may  be  employed  for  the  study  of  the  epithelium  of 


BY    DR.    KLEIN.  145 

different  parts.  It  is,  however,  better  to  cut  one  of  the  halves 
transversely  into  a  number  of  parts,  which  may  be  placed  in  a 
large  bottle  filled  with  half  or  one  per  cent,  solution  of  bichro- 
mate of  potash.  After  from  eight  to  ten  days,  sections  of  the 
cortex  are  prepared,  as  thin  as  possible.  Some  of  these  must 
he  made  in  the  direction  of  the  pyramidal  processes  (which  are 
readily  seeu  by  the  naked  eye),  others  at  right  angles  to  these 
processes,  and  parallel  to  the  surface.  Other  sections  com- 
prising as  much  of  the  medullary  substance  as  possible,  must 
in  like  manner  be  made  in  both  directions.  The  cross  sections 
should  be  taken  from  various  parts  of  the  medullary  substance, 
some  comprising  the  papillae,  others  the  intermediate  part. 
The  sections,  having  been  washed  in  water  for  fifteen  minutes 
or  more,  may  be  either  mounted  at  once  in  glycerin,  or  after 
previous  staining  for  twenty-four  hours  in  diluted  solution  of 
carmine.  Such  preparations  show  the  characters  of  the  epi- 
thelium in  the  tubes  throughout  their  whole  extent,  and  in  the 
loops  of  Henle.  It  may  be  farther  seen  that  in  many  of  the 
convuluted  tubes  of  the  cortex,  the  uniformly  granular  sub- 
stance can  be  distinguished  into  distinct  polyhedral  cells,  each 
possessing  a  spheroidal  nucleus.  By  teasing  the  sections  ob- 
tained as  above,  it  is  possible  to  isolate  straight  tubes  or  loops, 
but  this  can  be  better  accomplished  by  another  method  to  be 
described  further  on. 

Epithelium  of  the  Malpighian  Capsules. — For  the 
demonstration  of  the  epithelium  which  lines  the  internal 
surface  of  each  Malpighian  capsule,  and  the  surface  of  the 
glomerulus,  it  is  best  to  employ  kidneys  of  mature  or  imma- 
ture human  foetuses.  With  this  view  the  organ  (which  must 
be  as  fresh  as  possible)  must  be  divided  into  small  portions, 
and  first  placed  for  three  to  six  days  in  one  per  cent,  solu- 
tion of  bichromate  of  potash,  and  then  transferred  for  one  or 
two  days  into  one-fourth  to  one-eighth  per  cent,  solution  of 
chromic  acid.  The  sections  are  prepared  in  the  ordinary  way 
after  embedding.  In  such  preparations  it  is  seen  that  the 
capsule  of  the  glomerulus,  which  is  characterized  by  its  oblong 
nuclei,  extends  continuously  over  it,  and  that  it  is  lined  with 
a  continuous  layer  of  elements  which  are  mostly  cubical,  but 
sometimes  columnar.  The  epithelium  of  the  convoluted  tubes 
consists,  in  the  human  foetus,  of  spheroidal  or  cubical  cells. 
If  a  very  small  strip  of  the  fresh  kidney  of  the  frog  is  pre- 
pared in  salt  solution  or  serum,  it  is  seen  that  the  epithelium, 
as  well  of  the  capsule  as  of  the  commencement  of  the  con- 
voluted tube  leading  from  it,  is  beset  with  cilia  of  extraordi- 
nary length. 

Isolation  of  the  Tubes. — Long  slices  of  fresh  kidney  so 
cut  as  to  include  both  cortical  and  medullary  substance,  and 
to  extend  from  the  surface  to  the  papillae,  are  placed  in  a  flask 
10 


146  URINARY    APPARATUS. 

containing  a  mixture  of  eight  parts  of  common  alcohol,  and 
two  parts  of  hydrochloric  acid.  The  flask  is  fitted  with  a  cork, 
through  which  a  very  long  glass  tube  passes.  It  is  kept 
boiling  for  some  hours,  after  which  the  liquid  is  poured  away, 
and  replaced  by  distilled  water.  In  this  liquid  (which  should 
be  changed  once  or  twice)  the  portions  of  kidney  arc  steeped 
several  days.  They  are  then  agitated  in  a  test  tube,  contain- 
ing a  little  water,  by  which  means  the  tubes  readily  separate 
from  each  other.  They  can  now  be  prepared  in  the  same 
liquid  for  microscopical  examination,  or  allowed  to  subside, 
and  then  separated  from  the  liquid  and  mounted  in  glycerin. 
Pure  hydrochloric  acid  is  also  used  for  the  same  purpose. 
The  slices  of  kidney,  which  must  be  taken  from  an  animal 
killed  the  day  before,  are  steeped  in  hydrochloric  acid  of  1-120 
sp.  g.,  for  five  to  twenty  hours.  Thereupon  the  portions  are 
carefully  washed  with  distilled  water.  Of  these  methods,  the 
former  is  easier.  By  either  it  can  be  shown  that  the  capsule 
of  the  Malpighian  body  is  first  contracted,  and  then  dilated  so 
as  to  form  the  convoluted  urinary  tubes,  which  are  filled  with 
a  substance,  the  division  of  which  into  cells  is  almost  indis- 
tinguishable. These  tubes  are  continued  onwards,  first  as  the 
narrower  descending  limb  of  the  Henle's  loop,  and  then  as  the 
somewhat  wider  ascending  limb.  The  latter  again  dilates,  so 
as  to  form  the  intercalated  convoluted  tube  (Schaltsliick) 
wdiich  ends  in  a  straight  collecting  tube.  These  last  form  the 
pyramidal  processes,  and  unite  finally  into  single  ducts,  by 
repeated  junctions  with  each  other  at  very  acute  angles. 

The  whole  system  of  ducts  ma}r  often  be  injected  from  the 
ureter.  Injections  can,  however,  seldom  be  carried  beyond 
the  loops.  The  most  suitable  kidneys  for  the  purpose  are 
those  of  the  pig,  dog,  or  rabbit.  The  animal  must,  if  possible, 
be  killed  by  bleeding.  A  canula,  having  been  secured  in  the 
ureter,  close  to  the  point  at  which  it  leaves  the  pelvis  of  the 
kidney,  two  per  cent,  solution  of  Prussian  blue  is  injected, 
under  a  pressure  of  from  60  to  100  millimeters.  The  ureter 
having  been  ligatured,  it  is  desirable  to  fill  the  artery  with 
carmine  gelatin.  The  urinary  tubes  can  be  also  injected 
during  life  by  what  is  called  the  natural  method.  A  rabbit  of 
moderate  size  is  allowed  to  lose  10  c.  c.  of  blood  from  the 
jugular  vein,  replacing  it  with  a  filtered  solution  of  carmine, 
containing  two  drachms  of  carmine,  and  one  drachm  of  liquor 
ammoniac  in  an  ounce  of  water.  If  a  dog  of  moderate  size 
is  used,  25  c.  c.  are  required.  Immediately  after  the  injection, 
the  ureters  are  ligatured,  and  the  animal  is  allowed  to  live  for 
an  hour,  and  then  killed.  The  bloodvessels  are  then  injected 
with  solution  of  Prussian  blue  in  gelatin,  and  the  organ  is 
placed  in  common  alcohol  containing  a  drop  or  two  of  glacial 
acetic  acid.     Before  placing  the  kidneys  in  alcohol,  they  must 


BY    DR.    KLEIN.  147 

be  steeped  for  a  short  time  in  concentrated  solution  of  chloride 
of  potassium.  Instead  of  the  carmine,  solution  of  sulpho- 
indigotate  of  soda,  saturated  in  the  cold,  may  be  used  in 
exactly  the  same  manner.  The  bloodvessels  must,  however, 
be  subsequently  injected,  not  with  Prussian  blue,  but  with 
carmine  gelatin. 

Pelvis,  Ureter,  and  Bladder. — The  laminated  epithe- 
lium of  these  parts  may  be  studied  in  bichromate  of  potash 
preparations.  For  sections,  the  membrane  must  be  hardened 
in  chromic  acid.  The  methods  for  the  study  of  the  epithelium, 
muscular  tissue,  nerves,  and  ganglia,  etc.,  have  been  already 
fully  described  in  Part  I. 

Section  III. — Genital  Organs. 

Epithelium    and    Endothelium   of   Ovary. — It   has 

been  recently  shown  by  Waldeyer  that  the  ovary  is  only 
partly  covered  with  peritoneum.  Where  this  is  the  case  the 
surface  is  covered  with  endothelium.  The  remainder  of  the 
surface  possesses  a  cylindrical  epithelium,  to  which  the  term 
germinal  epithelium  is  applied.  This  can  be  demonstrated  in 
the  ovaries  of  the  sow,  bitch,  and  cat,  and  in  the  human 
ovary.  In  the  last  it  can  be  seen  both  in  the  mature  foetus 
and  in  the  adult.  In  the  fresh  ovary  the  line  of  demarcation 
can  be  made  out,  even  with  the  naked  eye.  By  scraping  the 
surface  with  a  scalpel,  shreds  can  be  obtained  which  may  be 
at  once  prepared  in  salt  solution.  In  those  taken  from  the 
peritoneal  part,  large  endothelial  plates  can  be  shown,  each 
containing  an  oblong  nucleus.  In  those  from  the  other  part, 
cylindrical  cells  are  seen,  which  consist  of  distinctly  granular 
protoplasm,  and  contain  an  ovoid  nucleus  and  nucleolus. 
These  possess  the  character  of  epithelial  elements.  If  an 
ovary  is  placed  a  few  minutes  in  silver  solution  and  then 
washed  the  usual  way  in  water,  and  hardened  in  alcohol, 
sections  parallel  with  the  surface  of  both  parts  may  be  pre- 
pared. In  such  sections,  if  made  close  to  the  surface,  and 
covered  in  glycerin,  the  contrast  between  the  two  forms  of 
cellular  investment  can  be  completely  demonstrated. 

The  anatomical  relations  of  the  germinal  epithelium,  and  of 
the  tunica  albuginea,  stroma,  and  Graafian  vesicles  must  be 
studied  in  sections.  For  this  purpose  the  fresh  organ  obtained 
from  any  of  the  above-mentioned  animals  must  be  steeped  in 
one  or  two  per  cent,  solution  of  bichromate  of  potash  for 
periods  varying  from  four  days  to  a  week ;  it  must  then  be 
transferred  for  a  day  or  two  to  one-eighth  or  one-tenth  per  cent, 
solution  of  chromic  acid,  and  can  afterwards  be  kept  in  com- 
mon alcohol.  Small  ovaries,  such  as  those  of  mature  foetuses, 
or  of  other  young  animals,  can  be  embedded  in  toto.  Larger 
organs  must  be  divided. 


148  GENITAL    ORGANS. 

Stroma. — The  most  important  peculiarity  to  notice  is  the 
extraordinary  frequency  of  bundles  of  spindle-shaped  cells 
which  run  across  each  other  in  various  directions.  Their  claim 
to  be  regarded  as  muscular  or  connective  tissue  cells  is  still 
open  to  question.  Both  in  the  sow  and  bitch,  there  are 
bundles  of  unstriped  muscular  fibres,  which,  along  with  blood- 
vessels, run  from  the  medullary  part  into  regions  in  which 
large  follicles  are  to  be  met  with,  and  form  an  investment  of 
the  follicular  wall.  There  are,  however,  many  bundles  in  the 
cortical  substance  which  present  no  such  definite  characters. 
But  in  the  ovary  of  the  guineapig,  muscular  bundles  can  be 
distinctly  recognized  even  in  the  stroma  of  the  cortex. 

Graafian  Follicles. — The  structure  of  these  follicles  can 
be  made  out  completely  in  the  preparations  above  referred  to. 
For  the  study  of  their  development,  human  fcetal  ovaries  and 
those  of  the  dog  must  be  used.  In  the  former,  it  is  seen  that 
from  that  part  of  the  surface  which  is  covered  with  germinal 
epithelium,  blind  tubes  are  sunk  to  various  depths  and  in 
various  directions.  These  tubes  are  lined  with  an  epithelium, 
which  is  continuous  with  that  of  the  surface,  and  identical 
with  it.  It  can  further  be  made  out  that  certain  individual 
elements  of  this  epithelium  have  a  special  character,  being 
more  readily  stained  with  carmine,  and  that  they  are  larger 
than  the  others.  Between  these  and  ovules  all  transitions 
can  be  observed.  By  the  segmentation  of  a  single  tube  into 
several  closed  vesicles,  Graafian  follicles  are  formed,  each  of 
which  is  lined  with  a  layer  of  epithelium,  and  contains  one  or 
two  nucleated  ovules,  so  that  both  stand  in  a  definite  develop- 
mental relation  to  the  germinal  epithelium.  These  facts  may 
be  demonstrated  equall}*  well  in  the  ovaiy  of  the  bitch  ;  a  zone 
of  tissue  exists  under  the  germinal  epithelium  in  which  closed 
tubes  are  met  with,  which  run  in  very  various  directions. 
Many  of  these  look  as  if  they  were  connected  with  each  other 
so  as  to  form  a  network.  Deeper,  there  is  a  zone  in  which 
separate  follicles  exist. 

Ovum  and  Discus  Proligerus. — The  ovum  itself  and 
the  cells  of  the  Discus  proligerus  may  be  studied  in  fresh 
ovaries.  The  contents  of  a  large  Graafian  vesicle  of  the 
rabbit's  or  guineapig's  ovary  are  discharged  on  to  an  object- 
glass  for  the  purpose.  The}'  can  also  be  well  seen  in  the  pre- 
parations above  described. 

Fallopian  Tubes,  Uterus,  Vagina,  and  External 
Organs. — These  may  be  best  studied  in  sections  of  organs 
hardened  in  chromic  acid — the  methods  recommended  in  Bart 
I.  being  employed  for  the  study  of  the  several  tissues  of 
which  they  consist.  Some  special  remarks  are,  however, 
necessary  relating  to  the  glands  of  the  uterus.  They  can  be 
best  demonstrated  in  the  cornua  uteri  of  bitches  or  cats  which 


BY    DK.    KLEIN.  149 

have  already  borne  young.  The  fresh  organ  is  placed  in 
common  alcohol  or  dilute  chromic  acid,  Avithout  opening  it; 
after  four  or  five  days  it  is  fit  for  making  sections.  Each 
gland  consists  of  long  blind  tubes,  which  may  be  either  single 
or  divided.  The  glands  are  closety  packed  together.  In  each 
tube  two  parts  may  be  distinguished ;  one  of  these,  which  may 
be  regarded  as  the  duct,  is  straight,  and  possesses  an  epithe- 
lium of  slender  pale  cylindrical  elements.  The  gland  proper 
is  convoluted,  and  consists  of  shorter  elements.  If  the  sec- 
tions are  steeped  twenty-four  hours  in  very  dilute  carmine,  it 
is  seen  that  this  epithelium  is  much  more  stained  than  that  of 
the  duct.  In  the  sow's  uterus,  and  in  those  of  the  rabbit  and 
mouse,  it  can  be  made  out  that  the  epithelium  is  ciliated. 

The  glands  can  be  best  prepared  in  lengths  from  the  preg- 
nant uterus  of  the  sow.  For  the  mode  of  preparation  see 
Chapter  III.,  p.  60.  It  is  scarcely  necessary  to  observe  that 
for  the  study  of  the  external  organs,  injected  preparations  are 
important. 

Male  Genital  Organs. — The  general  structural  relations 
of  the  testis  and  epididymis  are  best  studied  in  sections  of 
fresh  organs  (frog  or  mammalia),  hardened  in  common  alco- 
hol ;  these  must  be  stained  and  prepared  in  Dammar  varnish 
in  the  usual  way.  Preparations  with  the  bloodvessels  and 
lymphatics  injected  must  also  be  used.  The  latter  are  easily 
obtained  by  the  method  of  puncture.  The  characteristic  epi- 
thelium of  the  epididymis  must  be  seen  in  fresh  preparations 
in  serum,  as  well  as  in  sections.  The  structure  of  the  vasa 
deferentia^  vesiculae  seminales,  prostate,  urethra,  and  penis, 
may  be  all  studied  in  the  organs  of  the  fcetus  or  of  children, 
after  hardening  in  chromic  acid.  The  structure  of  the  erectile 
tissues  cannot  be  demonstrated  without  good  injected  prepa- 
rations. [For  details  see  the  author's  paper  in  Strieker's 
Hand-book. J 


150  ORGAN    OF   BIGHT. 


CHAPTER  XII. 
ORGANS  OF  SPECIAL  SENSE. 

Organ  of  Sight. — The  epithelium,  cellular  elements,  and 
the  finer  nerves  of  the  cornea  have  been  already  treated  of 
(Chapters  II.,  III.,  and  V.)«  We  have  only  to  remark  that, 
in  order  to  observe  the  relation  of  the  cornea  to  the  conjunc- 
tiva, sclerotica,  and  ligamentum  peclinatum,  it  is  necessary  to 
harden  the  bulb  entire,  and  to  make  sections  which  shall  in- 
clude all  these  structures.  The  best  and  simplest  method 
consists  in  placing  the  fresh  bulb  of  a  mature  foetus,  a  rabbit, 
a  pig,  or  a  calf,  in  one-tenth  per* cent,  solution  of  chromic  acid, 
for  eight  or  ten  days;  having  previously  made  two  or  three 
punctures  in  it  with  a  lancet-shaped  needle.  After  two  or 
three  daj-s  of  immersion,  the  bulb  may  be  cut  in  two  with  a 
razor,  the  crystalline  lens  and  vitreous  body  removed  with 
forceps,  and  the  anterior  half  of  the  bulb  (containing  the  con- 
junctiva, the  cornea,  the  iris,  and  processus  ciliares,  the  an- 
terior segment  of  the  sclerotic  and  choroid  as  well  as  the  ora 
serrata  retinse,  and  zonula  Zinii)  put  back  in  the  solution. 
The  necessary  consistence  having  been  obtained,  a  portion  is 
cut  off  in  such  a  way  as  to  render  it  possible  to  make  trans- 
verse sections  through  the  above-mentioned  structures.  The 
sections  ma}r  be  treated  in  the  ordinary  way  ;  and,  if  thin 
enough,  they  will  also  be  useful  for  the  purpose  of  studying 
the  tissue  of  the  sclerotic,  choroid,  ciliary  processes,  and  iris, 
as  well  as  of  the  musculus  tensor  choroidese. 

The  cellular  elements  of  the  sclerotic  may  be  further  de- 
monstrated in  surface  preparations  as  follows :  The  bulbus  oculi 
of  a  frog  having  been  extirpated,  is  carefullj*  freed  from  ad- 
herent connective  tissue  on  an  object-glass  ;  the  surface  of  the 
sclerotic  is  then  thoroughly  touched  with  lunar  caustic  :  after 
a  quarter  of  an  hour  small  portions  are  cut  off:  these  must  be 
pencilled  on  their  inner  surface  with  a  camel-hair  brush,  so  as 
to  remove  any  adhering  pigment ;  the  preparations  being 
finally  mounted  in  glycerin.  Successful  preparations  exhibit 
branched  clear  spaces — canaliculi — on  a  brownish-ground,  such 
as  have  been  previously  described. 

Other  portions  of  fresh  sclerotic  may,  after  pencilling,  be 
treated  with  a  half  per  cent,  solution  of  chloride  of  gold,  and 
employed  both  for  vertical  and  horizontal  sections.  In  the 
former,  the  violet-colored  cellular  elements  appear  as  spindle- 


BY    DR.    KLEIN.  151 

shaped  cells,  lying  between  the  bundles  of  connective  tissue  of 
the  sclerotic;  whilst, .in  the  latter,  they  exhibit  forms  which 
correspond  to  the  above-mentioned  canaliculi.  The  sclerotic 
of  a  young  rabbit  may  be  similarly  treated  with  the  gold  and 
silver  solutions.  For  the  study  of  the  iris,  choroid,  and  ciliary 
processes,  several  methods  are  employed  besides  that  of  making 
vertical  sections  through  the  hardened  parts.  The  hexagonal, 
pigmented  epithelium  covering  the  inner  surface  of  the  uvea, 
which  is  considered  to  belong  to  the  retina,  can  be  removed 
from  the  fresh  membrane  with  a  scalpel  or  sharp  needle,  in 
small  shreds :  these  must  be  spread  out  with  needles  and 
mounted  in  salt  solution.  Preparations  of  the  same  kind  can 
also  be  obtained  from  bulbs  which  have  been  kept  for  a  few 
weeks  in  Muller's  fluid  ;  they  must  be  preserved  in  glycerin. 
The  more  or  less  branched  pigment  cells  which  are  to  be  found 
in  the  substance  of  the  uvea  in  different  animals,  but  varying 
in  number  and  distribution,  may  be  prepared  from  the  fresh 
tissue  in  a  similar  manner,  but  it  is  preferable  to  make  thin 
sections  of  the  membrane.  For  the  investigation  of  the  mus- 
culus  tensor  choroids,  as  well  as  the  sphincter  pupillse,  verti- 
cal sections  of  the  human  uvea  from  a  bulb  hardened  in  chro- 
mic acid,  are  most  important ;  the  sections  must  be  immersed 
in  very  dilute  carmine  for  twenty-four  hours. 

To  demonstrate  the  dilator  et  sphincter  pupillse,  the  iris  of 
a  small  albino  rabbit  will  serve.  It  must  be  cut  out  with  great 
care,  and  after  having  been  pencilled  on  both  surfaces  with  a 
camel-hair  brush,  moistened  with  humor  aqueus,  must  be  im- 
mersed in  half  per  cent,  solution  of  chloride  of  gold  for  from 
thirty  to  forty  minutes,  whence  it  must  be  transferred  to  acidu- 
lated water.  There  is  also  another  plan  which  answers  satis- 
factorily :  *  The  bulb  of  a  similar  rabbit  is  placed  in  Midler's 
liquid  for  a  few  days,  the  cornea  having  been  previously  punc- 
tured. The  whole  iris  is  then  cut  out,  pencilled  in  the  same 
fluid  with  a  camel-hair  brush  on  both  sides,  and  placed  in  spirit 
for  from  fifteen  to  thirty  minutes.  The  iris  should  then  be 
colored  in  dilute  carmine,  and  portions  should  be  mounted  in 
glycerin.  With  the  exception  of  the  muscles,  the  bloodvessels 
form  the  most  important  part  of  the  uvea.  For  their  study, 
injections  witli  gelatin,  colored  by  carmine  or  Berlin  blue, 
should  be  made  ;  albino  animals  being  preferred.  For  small 
animals  the  canula  should  be  tied  into  the  root  of  the  aorta, 
the  aorta  ihoracica  descendens  being  ligatured.  For  large 
animals  the  common  carotid  may  be  employed  ;  of  course,  as 
a  general  rule,  onljr  one  eye  will  be  injected.  The  bulb  having 
been  kept  in  spirit  for  a  few  days,  the  whole  uvea  is  carefully 
isolated  from  the  outer  coats:  in  the  case  of  a  small  rabbit, 
one  section  may  be  mounted  including  a  portion  of  the  iris, 
ciliary  processes,  and  the  anterior  half  of  the  choroid  ;  and 


152  ORGAN   OF   SIGHT. 

another  including  a  portion  of  the  posterior  half  of  the  choroid. 
The  circuit  arteriosi  iriili.<  minor  et  major,  the  vessels  between 
these,  the  system  of  capillaries  of  the  ciliary  processes,  and 
their  relation  to  the  arterise  ciliares  posticse1  the  system  (ar- 
terial) of  the  laminae  Ruisehii,  and  the  tributaries  of  the  venae 
vo>  ticosae,  are  severally  to  be  studied. 

The  crystalline  lens,  with  its  several  parts  (capsule,  epithe- 
lium lining  the  inner  surface  of  the  anterior  portion,  and  the 
constituent  fibres  of  the  lens  itself)  should  be  made  the  subject 
of  careful  observation.  The  hyaline  capsule,  with  the  above- 
mentioned  epithelium,  can  be  demonstrated  in  a  perfectly  fresh 
preparation,  in  humor  aqueus.  The  structure  of  the  lens  fibres 
may  be  made  out  in  preparations  from  the  lens  of  a  fowl,  or  of 
some  large  mammal,  macerated  in  very  dilute  sulphuric  acid 
(one  or  two  per  cent.).  The  fibres  exhibit  a  striated  appear- 
ance, and,  if  they  are  sufficiently  separated  from  each  other, 
it  may  be  seen  that  each  possesses  a  spherical  nucleus. 

In  preparations  of  the  same  kind  from  the  portion  of  the 
lens  which  corresponds  to  the  margin  between  the  anterior 
and  posterior  half  of  the  organ,  every  stage  of  transition  of 
the  epithelium  which  lines  the  anterior  part  of  the  capsule, 
into  true  lens  fibres,  can  easily  be  made  out ;  the  elements  be- 
coming progressively  more  and  more  elongated,  and  their  nu- 
clei more  and  more  distant  from  their  bases.  The  best  way 
to  ascertain  these  facts  is  by  means  of  sections,  which  show 
also  that,  posteriorly,  the  lens  fibres  are  in  immediate  contact 
with  the  capsule.  Vertical  sections  display  the  very  regular 
mosaic  due  to  the  cutting  across  of  the  long,  hexagonal  fibres. 
They  may  be  made  after  the  lens  has  been  hardened  in  solu- 
tion of  chromic  acid  (one-tenth  per  cent.),  or  bichromate  of 
potash  (one-half  to  one  per  cent.).  The  hardening  ma}'  also 
be  effected  by  exposing  the  lens  to  the  air,  and  allowing  it  to 
become  almost  dry :  sections  so  obtained  must  be  mounted  in 
glycerin.  The  structure  of  the  corpus  vilreum,  consisting  as 
it  does  of  a  perfectly  hyaline  gelatinous  matrix,  with  a  few 
extremely  pale,  small  spheroidal  cells  imbedded  in  it,  may  be 
investigated  in  the  fresh  organ,  but  better  in  sections  made 
after  the  bulb  has  been  hardened  in  a  one-eighth  to  one-half 
per  cent,  solution  of  chromic  acid.  The  staining  of  the  sec- 
tions with  carmine  or  aqueous  solution  of  anilin  will  prove 
very  useful  for  the  demonstration  of  the  cellular  elements. 

The  retina  presents,  perhaps,  a  more  difficult  task  to  the 
histologist  than  any  other  organ  ;  the  investigation  of  even  the 
simplest  relations  of  its  constituent  elements  requiring  much 
time  and  patience.  The  introduction  of  the  perosmic-acid 
method  of  preparation,  however,  has,  within  the  last  few  years, 
considerably  bridged  over  our  difficulties  in  this  respect. 


BY    DR.    KLEIN.  158 

The  most  useful  preparations  are  those  made  with  needles. 
The  carefully  excised  fresh  eye  of  a  frog,  newt,  rabbit,  ox, 
calf,  or  pig  is  divided  into  an  anterior  and  posterior  half. 
The  latter  is  placed  for  from  twenty-four  to  forty-eight  hours 
in  a  one-tenth  per  cent,  solution  of  perosmic  acid,  in  the  dark; 
thence  it  is  transferred  to  distilled  water  for  twenty-four  hours. 
After  this  period  small  portions  of  the  retina  are  snipped  off 
and  teased  in  a  drop  of  nearly  saturated  solution  of  acetate 
of  potash  and  mounted  in  the  same  fluid.  The  frog's  retina 
in  particular  is  extremely  valuable  for  the  study  of  the  rods 
and  cones  with  their  outer  and  inner  portions,  the  radial  fibres, 
the  nuclei  of  the  outer  and  inner  granular  layers,  and  the  nerve 
fibres  and  ganglion  cells,  all  of  which  are  much  better  seen 
than  in  retinas  which  have  been  macerated  in  Midler's  liquid. 
When  the  object  is  to  study  the  relations  to  each  other  of  the 
different  strata  in  the  retina,  either  of  the  two  following  pro- 
cesses may  be  employed  : — 

1.  The  posterior  half  of  the  bulb  (or,  when  small,  the  whole 
bulb,  after  two  or  three  punctures  have  been  made  in  it),  is 
placed  in  a  two  per  cent,  solution  of  perosmic  acid  in  the  dark 
for  twenty-four  hours :  it  is  then  removed,  and  small,  oblong 
pieces  are  cut  from  it  with  a  razor  (these  including,  of  course, 
besides  retina,  corresponding  portions  of  sclerotic  and  choroid), 
and  placed  in  alcohol  for  twent3r-four  hours  or  more,  until  they 
have  attained  sufficient  consistence  for  sections  to  be  made 
from  them  after  embedding.  The  sections  should  be  mounted 
in  acetate  of  potash  as  before.  This  method  answers  very 
well  for  the  retina  of  the  rabbit,  calf,  or  pig. 

2.  The  other  plan,  which  must  also  be  looked  upon  as  a 
good  one,  is  the  treatment  with  Midler's  liquid.  The  entire 
bulb  of  one  of  the  above-mentioned  animals  is  placed  in  this 
liquid,  having  previously  been  punctured  at  two  or  three 
points.  After  from  three  to  five  weeks  it  is  taken  out,  and  cut 
into  an  anterior  and  a  posterior  half.  From  the  portion  of 
retina  belonging  to  the  latter,  an  oblong  piece  is  removed 
with  fine,  sharp  scissors  (it  is  generally  pretty  easy  to  do  this 
without  involving  the  sclerotic  and  choroid,  since  the  retina 
has  usually  become  more  or  less  separated  from  the  latter  by 
the  action  of  the  fluid),  and  transferred  for  a  few  days  to  ordi- 
nary  spirit.  From  this  it  is  put  into  dilute  carmine  solution 
for  twenty-four  hours,  then  washed  in  acidulated  water,  and, 
finally,  after  half  an  hour's  or  an  hour's  immersion  in  absolute 
alcohol,  is  embedded  in  the  manner  previously  described 
(Chapter  VI.).  The  sections  are  transferred  in  the  manner 
there  indicated  from  the  razor  to  the  object-glass,  on  which, 
after  proper  treatment,  they  are  to  be  mounted  in  Dammar. 

A  skilful  manipulator  can  obtain  good  results  with  this 
method.     Very  thin  sections  show,  in  a  sufficiently  clear  man- 


154  ORGAN    OF    HEARING. 

ner,  the  general  arrangement  of  the  rods  and  cones,  and  their 
illation  to  the  elements  of  the  outer  granular  layer,  that  of 
the  intermediate  layer  to  the  granules  of  the  inner  granular 
layer;  the  finely  granular  layer,  and  the  relation  of  its  fine 
fibrilla?  to  the  fibrils  of  the  inner  granular  layer  on  the  one 
side  and  the  processes  of  the  ganglion  cells  on  the  other;  and 
finally,  the  layer  of  nerve  fibres.  The  general  arrangement  of 
the  radial  fibres,  or,  rather,  bundles  of  radial  fibres,  may  be 
also  made  out :  each  bundle,  attached  to  the  Umitans  interna 
by  a  broad  basis,  enters  the  finely  granular  layer,  thence  pass- 
ing through  the  inner  granular  layer  (where  the  bundles  be- 
come ramified,  and  inclose  nuclei),  then  on  through  the  inter- 
mediate layer  and  outer  granular  layer  (where  again  ramifica- 
tions and  junctions  are  met  with)  to  become  attached,  finally, 
to  the  Umitans  externa.  (See  description  of  Figs.  139  and 
140). 

Organ  of  Hearing. — The  outer  part  of  this  organ,  including 
the  external  ear,  meatus,  and  Eustachian  tube,  should  be 
studied  in  portions  taken  from  a  3'oung  human  subject.  To 
prepare  the  membrana  tympani  (human,  or  from  a  cat  or  dog), 
it  must  be  exposed  b}"  the  aid  of  saw  and  bone-forceps — a 
manipulation  requiring  an  accurate  knowledge  of  the  topo- 
graphical details  of  the  temporal  bone.  This  done,  the  mem- 
brane is  excised,  and  either  stained  with  silver  at  once,  to 
show  the  epithelium  of  the  two  surfaces,  or  pencilled  on  its 
outer  surface  with  a  brush  moistened  with  serum,  to  show  the 
lymphatics.  If  the  gold  method  is  used,  the  epithelium  is  also 
pencilled  on  the  outer  surface,  and  the  membrane  immersed  in 
the  solution  from  half  an  hour  to  an  hour.  It  must  then  be 
treated  in  the  usual  way. 

The  study  of  the  membranous  labyrinth,  especially  the  canal 
of  the  cochlea  and  the  semicircular  canals — is  a  matter  re- 
quiring an  immense  deal  of  care  and  practice.  It  should  be 
undertaken  both  in  foetal  and  adult  organs.  For  the  examina- 
tion of  it  in  the  embyro,  a  foetal  calf  or  pig  from  ten  to  fifteen 
centimeters  long  may  be  used.  The  whole  cartilaginous  laby- 
rinth may  be  readily  separated  from  the  rest  of  the  skull  after 
the  maceration  of  the  latter  in  solution  of  bichromate  of  potash 
(half  to  one  per  cent.)  for  a  week  or  two.  After  separation  it 
is  placed  in  spirit  for  a  few  clays.  A  second  opening  (besides 
the  already  existing  fenestra  rotunda)  should  then  be  made 
on  the  side  opposite  to  it,  or,  better,  at  a  point  corresponding 
to  the  top  of  the  cochlea.  The  whole  organ  is  now  stuck  on 
a  needle  and  immersed  in  a  warm — but  of  course,  not  hot — 
mixture  of  wax  and  oil,  so  as  to  fill  up,  at  least  in  part,  the 
canals  which  exist  in  the  organ  ;  this  is  then  embedded  in  the 
ordinary  way,  marks  being  made  on  the  mass  for  the  purpose 
of  indicating  the  exact  position  of  the  preparation.     Sections 


BY    DR.    KLEIN.  155 

are  then  made  in  succession  across  the  axes  of  the  several 
canals,  and  are  stained  in  weak  carmine.  Such  sections,  being 
readily  obtained  in  a  perfect  state  in  the  foetus,  serve  as  a 
most  valuable  key  to  the  stud}'  of  the  adult  organ. 

The  fully-developed  organ  is  best  studied  in  the  ear  of  a  small 
dog,  guineapig,  or  new-born  child.  From  the  fresh  jaw  of  the 
guineapig  the  whole  of  the  petrous  portion  of  the  temporal  bone 
can  readily  be  removed,  and  placed  for  a  week  or  fortnight  in 
a  half  to  a  quarter  per  cent,  solution  of  chromic  acid,  to  which 
a  few  drops  of  hydrochloric  acid  has  been  previously  added, 
the  liquid  being  changed  once  or  twice  during  that  time.  The 
cochlea  is  then  removed,  and  after  remaining  in  spirit  for  a 
few  days,  is  filled  with  a  mixture  of  wax  and  oil  under  the 
air-pump.  Sections  are  prepared  as  before,  after  embedding. 
A  second  mode  should  also  be  employed,  which  is  as  follows  : 
A  horizontal  section  is  made  through  the  organ  after  removal 
from  the  spirit,  so  as  to  expose  all  the  turns  of  the  cochlear 
canal.  Both  halves  are  then  embedded  in  gelatin  solution,  to 
•which  a  few  drops  of  glycerin  has  been  added,  as  mentioned  in 
Chapter  VI.  The  transparency  of  the  gelatin  enables  us  to  be 
sure  of  the  direction  of  our  sections.  These  are  placed  first  in 
warm  water,  to  remove  the  gelatin.  They  may  be  then  mounted 
in  glycerin,  or  replaced  for  a  short  time  in  spirit,  stained  with 
carmine,  and  mounted  in  Dammar.  I  would,  however,  advise 
the  student  not  to  risk  the  manipulation  required  for  the  latter 
process,  but  to  mount  in  glycerin  at  once  after  the  warm  water  ; 
for  the  section,  if  it  is  as  thin  as  it  should  be,  would  stand  a 
considerable  chance  of  injury. 

For  the  stud}''  of  the  organ  of  Corti,  thin  vertical  parts  of 
sections  must  be  sought  for  in  which  the  lamina  spiralis  near 
that  organ  is  seen  to  be  cut  exactly  across:  this  is  more  par- 
ticularly the  case  when  the  situation  of  the  rods  of  the  arch  of 
Corti,  the  arrangement  of  the  cells  of  Deiter  and  the  ciliated 
cells,  and  the  distribution  of  the  nerves  of  the  membrana  basi- 
laris,  are  .under  examination.  To  show  the  elements  of  the 
membrana  reticularis,  and  the  epithelium  of  Reissner's  mem- 
brane, more  obliquely  cut  parts  of  the  section  are  to  be  chosen, 
or  even  portions  where  a  surface  view  of  these  structures  is 
obtainable. 

Organ  of  Taste. — For  the  study  of  the  organ  of  taste  the 
tongue  of  the  frog  or  rabbit  may  be  used.  In  the  former,  our 
attention  may  be  confined  to  the  papillae  fungiformes,  the  most 
important  subject  of  observation  being  the  topographical  rela- 
tions of  their  cellular  covering.  The  perfectly  fresh  organ  is 
spread  out  with  pins  on  a  plate  of  cork,  care  being  taken  to 
avoid  unequal  stretching,  and  placed  in  very  dilute  chromic 
acid.  Vertical  sections  are  then  made  in  the  usual  way. 
Another  way  is  to  color  the  fresh  organ,  spread  out  on  cork  as 


156  OROAN   OF   TASTE. 

above,  in  chloride  of  gold.  Half  an  hour's  steeping  in  half 
per  cent,  solution  is  sufficient ;  but  it  is  necessary,  before  cx- 
posing  the  preparation  in  water,  to  stream  it  thoroughly  with 
the  same  liquid,  in  order  to  avoid  the  subsequent  formation  of 
colored  deposit  on  the  surface.  As  soon  as  the  tongue  has 
assumed  the  proper  color,  it  must  be  hardened  in  alcohol,  for 
the  preparation  of  sections  which  must  be  prepared  in  glycerin. 
In  vertical  sections  of  fungiform  papillae  the  following  parts 
are  seen  :  In  the  axis  of  the  papilla,  along  with  the  vessels,  a 
nerve  twig  is  observed,  consisting  of  medullated  fibres,  which 
ascends  towards  the  summit  of  the  papilla,  and  there  pencils  out 
into  nerve  fibres.  Each  of  these  is  seen  eventually  to  end  in  a 
non-medullated  fibre.  Along  the  border  of  each  papilla  are 
seen  muscular  fibres  which  divide  dendritically  as  the}'  ascend. 
The  covering  of  the  flattened  summit  consists  of  a  relatively 
thick  layer,  in  which  two  strata  can  be  distinguished.  The  more 
superficial  of  these  is  thicker  and  paler,  and  is  finely  striated 
in  the  direction  of  the  long  axis  of  the  papilla.  In  thin  sec- 
tions it  can  be  recognized  that  this  material  consists  of  pale 
longitudinally  striated  cylinders.  The  deeper  and  thinner 
stratum  consists  of  a  ground-substance  deeply  stained  both  by 
gold  and  carmine,  in  which  several  layers  of  nucleus-like  struc- 
tures are  embedded.  It  can  be  made  out  in  very  thin  sections 
(and  also  in  teased  preparations)  that  the  cylindrical  nucleated 
cells  take  part  in  the  formation  of  both  layers,  the  outer  seg- 
ment of  each  cell  contributing  to  form  the  outer  stratum,  the 
other,  which  contains  the  nucleus,  the  inner  stratum.  The 
outer  segment  of  each  cell  is  pale  and  finely  streaked  longitu- 
dinally, while  the  inner  segment,  which  consists  of  granular 
protoplasm,  is  divided  towards  the  papilla  into  branched  pro- 
cesses, which  unite  with  each  other  and  with  those  of  neighbor- 
ing cells.  In  preparations  successfully  stained  with  gold,  it 
can  further  be  made  out,  that  the  non-medullated  fibres  re- 
solve themselves  into  a  network  of  extremely  fine  fibrils,  which 
spread  under  the  stratum  of  cells.  No  connection,  however, 
has  been  demonstrated  to  exist  between  this  network  and  the 
anastomosing  branched  processes  above  mentioned.  The  forms 
of  the  cylindrical  cells  should  be  also  studied  in  teased  prepara- 
tions. Strips  of  fresh  mucous  membrane  are  placed  in  the 
dark  for  from  twent3'-four  to  fort3'-eight  hours,  in  one-tenth 
per  cent,  solution  of  perosmic  acid.  The  object  having  been 
steeped  in  water  one  or  two  daj's,  shreds  must  be  torn  off  the 
free  surface  of  each  strip  of  membrane,  with  fine  sharp  needles. 
Each  of  these  shreds,  having  further  been  teased  carefully  with 
needles,  must  then  be  mounted  in  a  drop  of  acetate  of  potash. 
Another  method  consists  in  macerating  similar  strips  in  iodized 
serum,  solution  of  bichromate  of  potash,  or  very  dilute  solution 


BY   DR.    KLEIN.  157 

of  chromic  acid  (one-twentieth  per  cent.).     The  teased  prepara- 
tions must  be  mounted  in  glycerin. 

At  the  edge  which  unites  the  dorsal  and  lateral  surfaces  of 
the  tongue  of  the  rabbit,  a  round  or  oval  depression  is  seen, 
on  the  surface  of  which  an  arrangement  of  furrows  with  inter- 
mediate ridges  are  visible  to  the  naked  eye.  If  a  vertical  sec- 
tion is  made  of  this  part,  in  a  tongue  hardened  in  one-tenth  per 
cent,  chromic  acid,  in  such  a  direction  that  the  plane  of  section 
crosses  the  ridges,  a  meshwork  of  trabecular  of  striped  muscular 
fibres,  in  the  spaces  of  which  the  numerous  mucous  glands  are 
embedded,  can  be  recognized.  The  short  ducts  of  these  glands 
rise  for  the  most  part  vertically,  but  occasionally  obliquely  to 
the  surface  ;  alwa3rs  opening  into  the  splits  between  the  ridges. 
So  much  of  the  mucosa  as  lies  underneath  the  furrows  and 
ridges,  contains  a  great  number  of  non-medullated  nerve-fibres. 
Each  ridge  is  covered  with  a  laj'er  of  epithelium  which  becomes 
thicker  upwards,  i.  e.,  towards  the  arete ;  and  on  either  aspect 
of  each  ridge,  certain  bodies  are  seen,  embedded  in  the  surface 
b}T  which  it  looks  towards  its  neighbor :  to  these  the  term  taste 
goblets  (Geschmacksbecher)  has  been  applied.  They  are,  as 
the  term  indicates,  bell  or  cup-shaped  structures,  which  are 
limited  by  a  special  layer  of  flattened  epithelium  cells,  which  in 
profile  look  spindle-shaped.  Into  the  space  inclosed  within 
this  layer,  there  projects  from  the  mucosa  a  bunch  of  oblong 
spindle-shaped  cells,  which  towards  their  bases  appear  to  be 
divided.  Each  contains  an  oblong  nucleus.  The  forms  of  the 
elements  just  described,  and  of  those  which  constitute  the  outer 
wall  or  investment  of  each  goblet,  should  be  studied  in  teased 
preparations.  The  circumvallate  papillae  of  the  human  tongue 
and  of  other  mammalia  exhibit  similar  structures. 

Organ  of  Smell. — Teased  preparations  can  be  obtained 
by  macerating  the  olfactoiy  mucous  membrane  of  the  frog 
or  of  mammalia  in  one-twentieth  per  cent,  chromic  acid,  in 
Miiller's  liquid,  or  iodized  serum,  or  perosmic  acid.  The  whole 
of  the  head  of  the  frog,  after  removing  the  lower  jaw,  and 
opening  the  nares,  is  placed  in  the  liquid.  In  mammalia,  the 
nares  can  be  opened  in  the  middle  line,  after  Avhich  portions  of 
the  olfactory  tract  can  be  removed.  For  the  preparation  of 
sections,  the  parts  must  be  kept  in  one-fifth  per  cent,  solution 
of  chromic  acid,  which  must  be  renewed  as  often  as  necessary 
till  the  bone  becomes  soft.  In  teased  preparations  it  is  seen 
that  there  is  no  marked  distinction  between  the  ordinary  coni- 
cal epithelial  cells  and  the  special  spindle-shaped  cells,  recog- 
nized as  olfactory  epithelium:  for  they  are  connected  together 
by  a  continuous  series  of  transitional  forms.  The  most  char- 
acteristic form  of  the  olfactory  cells  is  drawn  out  at  both  ends, 
viz.,  towards  the  mucosa  into  an  extremely  slender  filament, 
which  exhibits  granular  swellings  ;  and  towards  the  surface 


158  EMBRYOLOGY. 

into  a  somewhat  stouter  fibre,  which  is  streaked  longitudinally, 
like  the  ordinary  epithelial  element,  and  like  it,  bears  at  its 
extremity  a  bunch  of  cilia  ;  but,  as  has  been  already  said,  exam- 
ples are  met  with,  in  which  the  special  peculiarities  arc  wanting. 
In  the  frog,  the  processes  of  the  epithelial  elements  appear 
to  penetrate  the  mucosa,  so  as  to  form  a  network  of  fine  trabe- 
cular The  finest  branches  of  the  olfactory  nerve  are  seen  to 
tend  towards  this  network,  but  have  not  been  traced  into  actual 
continuity  with  the  extremities  of  the  so-called  olfactory  cells. 
The  mucosa  and  its  glands  must  be  studied  in  sections. 


CHAPTER  XIII. 
EMBRYOLOGY. 

In  treating  of  the  methods  which  are  commonly  employed 
in  the  study  of  general  embiyology,  we  shall  follow  the  same 
plan  as  in  special  histology  ;  noticing  only  those  points  which 
are  of  importance  to  the  beginner. 

As  is  well  known,  three  parts  are  distinguished  in  every 
mature  egg:  the  vitelline  membrane,  the  yolk  or  vitellus,  and 
the  germ.  The  last-mentioned  is  the  essential  part,  and  as- 
similates itself  to  the  general  idea  of  the  cell,  viz.,  an  organism 
composed  of  protoplasm,  which  possesses  the  capability,  under 
certain  conditions,  of  performing  amoeboid  movements.  In 
the  protoplasm  of  the  germ  the  germinal  vesicle,  a  body 
analogous  to  the  nucleus  of  other  cells,  is  embedded;  and 
within  this  lies  the  germinal  spot,  the  analogue  of  the  nucleo- 
lus. According  as  the  two  elements  of  the  egg,  which  are 
inclosed  by  the  vitelline  membrane,  viz.,  germ  and  yolk,  exist 
separately  from  one  another,  or  form  a  single  bod}',  eggs  are 
subdivided  into  two  large  groups,  viz.,  meroblastic  eggs,  in 
which  the  germ  is  separate  from  the  }'olk — such  as  those  of 
the  bony  fishes,  scaly  reptiles,  and  birds  ;  and  holoblastic  eggs, 
in  which  the  germ  itself  contains  the  elements  of  the  yolk — 
those  of  the  cartilaginous  fishes,  amphibia,  and  mammals. 

In  eggs  of  the  first  group,  the  germ  lies  upon  the  yolk  in 
the  form  of  a  disk;  for  which  reason  it  receives  the  name  of 
blastoderm  :  formerly  it  used  also  to  be  termed  (after  Reichert) 
"  formative  yolk,"  while  the  yolk  itself  was  called  "  nutritive 
3'olk."  The  first  process  that  claims  the  attention  of  the 
embryologist  is  cleavage.  The  fertilization  of  the  egg  sets 
this  process  going.  It  is  called  cleavage  because  the  germ 
divides  into  two  cleavage  masses,  each  of  these  again  into  two, 


BY    DR.   KLEIN.  159 

and  so  on,  until  the  whole  germ  is  divided  into  a  number  of 
globules,  each  of  which  consists  of  protoplasm  inclosing  a 
vesicular  nucleus,  and,  like  the  entire  germ,  is  endowed  with 
the  capability  of  performing  amoeboid  movements.  These 
cleavage  globules  are  called  "  embryo  cells."  Only  the  germ 
or  blastoderm  takes  part  in  the  cleavage,  since  this  alone  is 
endowed  with  amoeboid  movement.  Consequently  in  mero- 
blastic  eggs  the  cleavage  is  said  to  be  partial.  In  the  holo- 
blastic,  on  the  other  hand,  the  whole  egg  divides,  for  the  whole 
is  germ  ;  it  is,  therefore,  said  to  exhibit  total  cleavage. 

Study  of  the  Process  of  Cleavage  in  the  Ova  of 
Fish  and  Amphibia. — The  cleavage  process  should  be 
studied,  in  the  first  place,  in  the  entire  ovum  ;  the  knowledge 
thus  gained  being  completed  by  sections  of  the  germ  at  the 
cleavage  time.  Of  meroblastic  eggs,  those  of  the  trout  are 
best  suited  for  this  study.  Several  such  eggs  are  examined 
under  the  microscope  in  a  watch-glass,  in  the  water  in  which 
the}'  have  lain  since  undergoing  fertilization,  strong  trans- 
mitted light  and  a  weak  magnifying  power  (90-100)  being 
employed  (see  figs.  159-163).  At  the  tenth  hour  after  fertiliza- 
tion, the  blastoderm  appears,  lying  upon  the  yolk  like  a  lid 
over  a  saucer-shaped  depression  ;  the  yolk,  which  forms  the 
bottom  of  this  cavitj',  contains  closely  packed  oil  globules, 
which  have  become  aggregated  at  this  pole  of  the  yolk  since 
the  time  of  fertilization.  In  the  blastoderm  amoeboid  move- 
ments are  observable.  About  the  twelfth  hour,  the  first  cleav- 
age line  appears.  About  the  twenty-seventh,  almost  all  the 
eggs  show  two  cleavage  lines  crossing  each  other.  Between 
this  time  and  the  end  of  the  second  day,  eight  segments  may 
be  distinguished  ;  so  that  four  cleavage  lines  are  now  seen  on 
the  surface  of  the  blastoderm.  At  the  end  of  the  seventh 
day  the  process  of  cleavage  has  progressed  so  far  that  the 
surface  of  the  blastoderm  appears  beset  with  a  number  of 
bosses,  like  a  mulberry.  The  cleavage  process  is  far  more 
easily  studied  in  the  holoblastic  eggs  of  amphibia.  If  eggs  of 
the  frog  or  toad,  freshly  spawned,  are  placed  under  the  micro- 
scope, in  a  small  cell,  which  may  be  conveniently  prepared  upon 
a  slide  by  means  of  putty,  it  is  seen  (especially  in  the  case  of 
the  latter,  where  they  are  placed  one  behind  the  other  in  rows 
in  gelatinous  strings),  that  only  a  very  few  are  spherical: 
generally  one  part  of  the  surface  is  flattened:  so  that  it 
frequently  happens  that,  in  a  long  row  of  eggs,  alternating 
conical  ones  are  met  with.  About  the  sixth  or  seventh  hour 
after  spawning,  it  can  be  seen  by  transmitted  light  that  most 
of  the  eggs  have  become  round.  As  this  period  of  time  ap- 
proaches, the  amoeboid  movement  of  the  germ  becomes  more 
distinctly  visible,  presenting  the  appearance  of  an  oscillation 
at  some  point  or  other  within  the  vitelline  membrane.     This 


160  EMBRYOLOGY. 

appearance  gradually  increases,  until  a  slight  indentation  like 
a  notch  is  seen  at  some  part  of  the  margin  by  transmitted 
light.  This  first  notch  fills  up,  but  soon  a  similar  notch  occurs 
in  another  spot,  which  is  permanent.  By  strong  reflected  light, 
if  the  egg  lies  in  such  a  position  that  the  white  pole  is  directed 
downwards,  a  crater-like  dimple  may  be  seen  on  the  surface. 
This  dimple  extends  itself  over  the  margin  of  the  hemisphere, 
diminishing  at  the  same  time  gradually  in  depth.  It  is  called 
the  plaited  band  (Faltenkranz),  because  a  number  of  smaller 
creases  proceed  from  it  at  right  angles.  This  appearance  owes 
its  name  to  the  erroneous  impression  that  it  is  due  to  a  folding 
of  the  vitelline  membrane,  but  in  reality  it  merely  depends  on 
the  amoeboid  movement  of  the  germ.  In  fact,  it  is  possible, 
by  close  observation,  to  convince  one's  self  that  the  furrows 
of  the  plaited  band  are  subject  to  active  changes,  for  succes- 
sive groups  of  them  disappear,  again  crop  up,  become  more 
extensive  and  deeper,  and  then  again  retire.  After  a  longer 
or  shorter  time — commonly  one  hour  from  the  appearance  of 
the  first  dimple — one  of  the  folds  of  the  plaited  circle  becomes 
deeper,  and  spreads  itself  more  and  more  towards  the  periphery 
of  the  hemisphere,  whilst  the  others  gradually  disappear. 
Eventually  a  deep  cruciform  furrow  is  apparent  in  the  hemi- 
sphere we  have  hitherto  had  under  observation,  and  which,  as 
previously  stated,  is  on  the  opposite  side  to  the  white  pole. 
We  will  call  this  the  upper  hemisphere.  At  this  time,  only 
a  single  shallow  furrow  is  seen  in  the  lower  hemisphere. 
Subsequently  the  furrowing  proceeds  somewhat  more  rapidly  ; 
for  the  third,  or  equatorial  furrow,  occurs  half  an  hour  after; 
other  furrows  then  appear  at  right  angles  to  the  three  first 
formed,  generally  in  the  same  succession  in  which  the  principal 
furrows  have  originated;  from  these  secondaiy  furrows  of  the 
first  order  proceed  others  of  the  second,  and  from  these,  others 
of  the  third,  and  so  on.  The  upper  hemisphere  divides  much 
more  quickly  than  the  lower. 

The  ova  of  the  trout  are  prepared  as  follows :  The  egg  is 
placed  upon  an  object-glass  between  the  points  of  a  broad  pair 
of  forceps,  so  that  the  blastoderm  is  uppermost ;  the  forceps 
are  held  with  their  blades  at  a  fixed  distance  from  each  other, 
while  the  egg  is  pierced  near  its  equator  with  a  lance-shaped 
knife.  On  rapidly  withdrawing  the  knife  it  generally  happens 
that  the  blastoderm  in  loto,  with  a  large  part  of  the  tenacious 
semi-fluid  yolk,  spirts  out.  The  object  must  now  be  surrounded 
with  a  ring  of  putty  and  covered.  The  attention  of  the  ob- 
server should  be  directed  to  the  appearance  of  the  elements, 
their  amoeboid  movement,  and  to  the  various  forms  of  cleavage. 
The  preparation  of  the  ova  of  Batrachia  is  far  simpler.  The 
egg  is  placed  upon  an  object-glass,  and  as  much  as  possible  of 
the  gelatinous  investment  is  removed  with  the  aid  of  forceps 


BY    DR.    KLEIN.  161 

and  scissors.  The  vitelline  membrane  is  ruptured  by  means  of 
needles,  and  a  small  portion  of  the  escaping  contents  is  spread 
out  in  a  very  thin  layer.  If  the  egg  is  not  more  than  three 
days  old,  it  can  be  investigated  under  low  powers  (Hartnack's 
5  or  7)  without  a  cover-glass.  The  yolk  disks  should  be  espe- 
cially observed,  and  the  active  movements  of  the  pigment 
granules  with  which  the  embryo  cells  are  filled.  Attention 
should  be  further  directed  to  the  hyaline  prominences  which 
the  latter  send  out  and  retract,  particularly  after  the  addition 
of  a  very  small  drop  of  distilled  water. 

The  Cleavage  Cavity. —  The  second  important  point,  to 
which  the  embryologist  should  direct  his  attention,  is  the 
cleavage  cavity.  In  the  trout,  this  comes  into  existence  towards 
the  end  of  the  cleavage  pi*ocess.  The  blastoderm  appears  to 
be  separated  from  the  yolk  of  the  saucer-shaped  depression  by 
a  cavity  which  gradually  increases  in  width  and  depth.  The 
blastoderm  is  not,  however,  entirely  detached  from  the  yolk, 
but  remains  connected  with  it  here  and  there  by  chains  of  cells. 
These  chains  of  cells — "  sub-germinal  processes" — may  be  com- 
pared to  columns  by  means  of  which  the  blastoderm  rests 
upon  the  yolk  (see  fig.  167).  The  cells  of  the  sub-germinal 
processes,  like  those  of  the  deeper  layer  of  the  blastoderm,  are 
larger  and  more  coarsely  granular  than  those  of  the  more 
superficial  layers.  By  degrees  the  cells  of  the  sub-germinal 
processes  become  separated  from  the  blastoderm,  and  lie  upon 
the  floor  of  the  cleavage  cavity.  The  elements  which  are  found 
in  this  position  are  characterized  by  their  greater  size,  and  by 
their  distinctly  granular  appearance ;  they  are  products  of  the 
blastoderm,  which  are  either  left  lying  on  the  floor  of  the  cavity 
when  it  is  formed  by  the  raising  of  the  blastoderm  from  the 
yolk,  or  fall  to  the  bottom  of  the  cavity  as  it  increases  in  size. 

For  the  study  of  the  formation  of  the  cavity,  that  is,  of  the 
elements  which  are  to  be  found  on  its  floor  (the  destination'of 
which  we  shall  again  have  occasion  to  mention)  and  of  the 
simultaneous  expansion  of  the  blastoderm  over  the  cavity, 
sections  are  alone  available.  Eggs  of  the  requisite  stage  (10- 
14  days)  are  placed  in  a  very  dilute  (one-tenth  per  cent.)  solu- 
tion of  chromic  acid,  the  liquid  being  frequently  changed. 
After  a  few  days  the  eggs  will  have  become  almost  black  and 
quite  friable.  An  egg  is  now  pierced  with  a  lance-shaped  needle, 
and  the  vitelline  membrane  carefully  torn  open  at  one  place 
by  means  of  sharp  forceps,  the  rent  being  extended  in  a  hori- 
zontal direction  until  it  describes  a  complete  circle ;  the  mem- 
brane is  then  removed  from  the  upper  hemisphere,  which  con- 
tains the  blastoderm.  Thereupon  the  blastoderm,  together 
with  the  whole  of  the  yolk  of  the  saucer-shaped  depression,  is 
separated  by  a  sharp  scalpel  and  placed  in  dilute  alcohol,  where 
it  may  remain  for  any  length  of  time.  It  is,  however,  ready 
11 


162  EMBRYOLOGY. 

for  further  treatment  in  one  or  two  hours.  It  may  he  stained 
by  steeping  it  for  twenty-four  hours  in  very  dilute  carmine 
(see  Chapter  VII.),  anil  it  is  then  washed  in  weakly  acidulated 
water.  The  object  is  now  placed  in  absolute  alcohol  for  from 
half  an  hour  to  an  hour.  After  this,  it  is  embedded  in  the 
following  manner:  A  layer  of  the  mass  used  for  embedding 
(wax  and  oil)  is  poured  upon  aflat  piece  of  glass,  wood,  or  cork, 
or  into  a  little  box,  and  is  allowed  to  harden  ;  the  object,  after 
its  surface  has  been  earefull}'  dried,  is  placed  in  the  desired 
position  upon  this  mass,  and  a  further  layer  is  poured  around 
and  OArer  it,  which  must  be  warm,  but  not  too  hot.  When  the 
mass  is  thoroughl}-  solidified,  sections  are  made  as  follows: 
The  razor  is  moistened,  by  means  of  a  small  brush,  with  oil  of 
cloves  or  with  turpentine,  and  a  section  made,  which  is  floated 
off  from  the  razor  to  an  object-glass  with  oil  of  cloves.  When 
the  section  is  thoroughly  transparent,  a  process  which  occupies 
a  few  seconds,  or  at  most  minutes,  if  the  object  has  been  long 
enough  in  absolute  alcohol  before  embedding,  the  excess  of  oil 
of  cloves  is  to  be  carefully  soaked  up  with  strips  of  filter-paper. 
A  window  is  cut  out  of  fine  tissue  paper,  and  applied  to  the 
preparation  in  such  a  way  as  to  afford  protection  from  the 
pressure  of  the  cover-glass.  A  drop  of  Dammar  varnish  is 
allowed  to  fall  upon  the  preparation  thus  inclosed  b}r  the  paper, 
and  the  whole  is  covered.  The  eggs  having  been  placed  in 
one-tenth  per  cent,  solution  of  chromic  acid  until  the  gelatinous 
investment  is  entirely  dissolved,  they  are  transferred  to  common 
alcohol  for  two  or  three  days  and  then  preserved  in  glycerin. 
They  may  be  used  even  after  an  interval  of  months. 

For  the  study  of  the  cleavage-cavity  of  Batrachia,  sections 
should  be  made  of  the  eggs  of  Bufo,  beginning  with  the  stage 
at  which  the  first  furrows  are  already  formed.  The  egg  is 
taken,  by  means  of  a  spoon,  out  of  the  glycerin,  dried  with 
filter-paper,  and  embedded  according  to  the  method  above 
described.  The  razor  in  this  case  is  to  be  moistened  with 
absolute  alcohol,  and  the  sections  floated  on  to  the  object- 
glass,  with  the  same  liquid.  The  alcohol  is  removed  by  filter- 
paper,  and  the  section  moistened  with  a  drop  of  oil  of  cloves, 
after  which  the  process  is  the  same  as  above.  Batrachian 
eggs  require  great  care  and  attention,  both  in  making  and 
handling  the  sections;  first,  because  the  ovum  is  less  easily 
fixed  than  is  the  case  with  the  disk-like  germ  of  the  trout  or 
chick,  and,  further,  because  it  is  extremel}r  friable,  so  that 
sometimes,  out  often  sections,  only  one  will  be  brought  entire 
under  the  cover-glass.  The  first  indication  of  a  cavity  may 
be  traced  shortly  after  the  appearance  of  the  first  two  furrows. 
In  sections  made  at  this  stage,  it  is  seen  that  the  upper  two 
quarters  of  the  germ,  that  is  to  say,  those  furthest  removed 
from  the  white  pole,  and  which  are  always  smaller  than  the 


BY   DR.    KLEIN.  163 

two  lower,  are  rounded  off  at  their  inner  angles,  i.e.,  those 
turned  towards  the  centre  of  the  germ,  as  if  they  had  retracted 
from  it ;  the  lower  two,  also,  are  somewhat  rounded  at  their 
inner  angles,  but  not  so  markedly  as  those  above :  by  this 
means  a  small  cavity  is  formed,  which  lies  just  in  the  place 
where  the  four  segments  meet.  In  sections  of  progressively 
later  stages,  it  will  be  observed,  in  the  first  place,  that  the 
upper  segments  have  undergone  cleavage  much  more  rapidly 
— in  other  words,  that  their  elements  are  considerably  smaller  ; 
and,  secondly,  that  the  cavity  becomes  enlarged  at  the  expense 
of  the  upper  half  of  the  germ.  In  a  still  later  stage  of  cleavage, 
forms  will  be  met  with  in  which  the  cavity  takes  up  the  greater 
part  of  the  space  occupied  by  the  upper  segments.  The  cavity 
is  spanned  by  a  thin  dome,  consisting  of  only  two  or  three 
layers  of  small  elements;  whilst  its  floor  is  flat  and  lined  by 
larger  elements  belonging  to  the  lower  segments.  Under- 
neath these  elements,  which  still  contain  pigment,  elements 
occur  which  become  larger  as  the  white  pole  is  approached. 
At  this  time  it  may  be  observed,  that  these  large  elements — 
which  may  be  termed  ''formative  elements" — spread  upwards 
from  the  floor  of  the  cavity  over  the  under  surface  of  the  dome, 
until  at  last  a  stage  is  reached  at  which  the  whole  of  that  sur- 
face is  covered  with  them.  In  the  middle  part  of  the  dome 
these  formative  elements  are  disposed  in  a  single  layer ;  on 
the  parts  which  are  in  closer  proximity  to  the  floor  of  the 
cavity,  the  number  of  layers  is  greater.  The  dome  consists, 
therefore,  at  this  stage,  in  the  first  place,  of  two  or,  at  most, 
three  layers  of  small  elements  which  originally  belonged  to  it 
(and  which  are  also  continuous  with  the  cortex  of  the  rest  of 
the  germ)  ;  and  secondly,  below  these,  in  its  central  part,  of  a 
layer  of  larger  elements,  which  before  formed  part  of  the  floor 
of  the  cavity. 

Simultaneously  with  the  changes  just  mentioned,  another 
important  change  occurs  at  the  white  pole,  as  may  be  ascer- 
tained by  the  stud}'  of  sections  at  different  stages.  This  pole 
has  been  getting  gradually  smaller,  and  now  presents  the 
appearance  of  a  sharply  bounded  white  patch  of  the  size  of  a 
pin's  head — the  so-called  yolk-plug  (Dotterpfropf ).  A  fissure 
occurs,  which  constantly  extends  further  and  further  upwards, 
increasing  at  the  same  time  in  width,  until  it  gradually  ex- 
pands to  a  cavit}',  which  is  eventually  only  separated  from  the 
cleavage-cavity  by  a  single  layer  of  the  larger  elements.  As 
this  cavity  (called  the  visceral  cavity,  Rusconi's  cavity, 
Leibeshohle)  increases,  the  cleavage-cavity  diminishes.  In 
consequence  of  these  changes,  the  position  of  the  egg  is 
altered  ;  that  which  before  was  the  upper  half  now  becoming 
the  lower.  (As  regards  the  formation  of  the  cleavage  and 
visceral-cavities,  compare  figs.  169-173.) 


1G4  EMBRYOLOGY. 

Formation  of  the  Lamellae  of  the  Blastoderm. — 
From  a  comparative  study  of  sections  of  the  egg  of  the  trout 
at  successive  stages,  from  that  at  which  the  blastoderm  begins 
to  form  a  cover  over  the  saucer-shaped  depression,  consisting 
of  a  middle  thinner,  and  a  peripheral  thicker  part  (marginal 
swelling — Randwulst),  to  that  at  which  it  lias  already  grown 
round  a  quarter  of  the  yolk  and  exhibits  the  first  trace  of  the 
formation  of  an  embyro,  the  following  facts  ma}-  be  made  out: 
The  large  elements  found  on  the  floor  of  the  cavity  gradually 
tend  towards  the  periphery  of  the  blastoderm,  where  they  form 
the  peripheral  thickening,  or  marginal  swelling  already  men- 
tioned (see  fig.  168).  As  this  occurs  the  central  part  of  the 
blastoderm  by  degrees  becomes  so  thin,  that  it  consists  at 
length  of  only  two  layers  of  cells,  an  upper  lamella  of  flattened 
elements,  and  a  lower  containing  loosely  arranged  spherical 
elements  (in  single  or,  here  and  there,  in  double  series). 
These  two  layers  are  continuous  with  the  marginal  swelling, 
the  upper  layer  of  which  also  consists  of  flattened  elements, 
the  lower  of  one  or  two  strata  of  more  or  less  cylindrical  cells. 
In  the  marginal  swelling  two  other  strata  exist  underneath 
these  layers,  each  of  which  consists  of  large  spherical  elements, 
and  is  at  least  two  cells  deep.  We  have  therefore  in  the  mar- 
ginal swelling,  by  the  thickening  of  which  the  rudiment  of  the 
embyro  is  formed,  four  layers,  the  upper  or  corneal  layer 
(Hornblatt)  ;  a  second,  or,  as  it  may  be  termed,  nervous 
stratum,  because  out  of  it  is  formed  the  central  nervous  sys- 
tem ;  a  third  or  motor-germinative  ;  and  a  fourth,  or  epithelial 
glandular  layer  (Darmdr'ilsenblatt).  Of  these  four  layers  the 
two  lower  must  be  attributed  to  the  formative  elements  which 
come  from  the  floor  of  the  cavity. 

To  the  conditions  just  described  those  found  in  the  batra- 
chian  egg  are  analogous.  The  mode  in  which,  during  the 
formation  of  the  cleavage-cavity,  formative  elements  spread 
from  its  floor  over  the  under  surface  of  the  dome,  adding  a 
third  stratum  to  the  two  of  which  it  alread}'  consists,  has  been 
already  described.  This  third  layer  then  splits  into  two, 
whilst  the  visceral  cavity  is  growing  upwards  into  the  dome. 
At  a  point  which  corresponds  to  the  central  part  of  the  cavity 
the  cortex  becomes  thicker:  this  thickening,  which  is  formed 
at  the  cost  of  the  second  layer,  is  the  rudiment  of  the  central 
nervous  system  of  the  embyro.  We  find  the  same  four  layers 
in  the  egg  of  Batrachia — the  corneal,  the  nervous,  the  motor- 
germinative,  and  the  epithelial  glandular  (Darmdrusenblatt)  : 
the  last  two  of  which,  as  in  the  ovum  of  the  trout,  are  derived 
from  the  formative  elements  of  the  floor  of  the  cleavage-cavity 
(see  fig.  1 73). 

Cleavage  Cavity  of  the  Chick. — For  the  study  of  the 
cleavage  process  and  formation  of  the  cleavage-cavity,  in  the 


BY    DR.    KLEIN.  165 

blastoderm  of  the  chick,  it  is  necessary  to  intercept  the  eggs 
in  their  passage  through  the  Fallopian  tube ;  for  in  eggs  which 
are  already  laid,  these  processes  have  been  gone  through. 
The  investigation  of  these  phenomena  is  expensive,  and  de- 
pends somewhat  on  chance.  Hens  known  to  be  in  the  habit 
of  laying  eggs  in  spring  and  summer  must  be  sacrificed. 
Eggs  may  be  examined  in  which  the  shell  is  either  absent  or 
consists  of  a  very  thin  parchment-like  structure,  or  is  in  pro- 
cess of  calcification.  They  are  placed  for  a  few  days  in  a  deep 
capsule  containing  a  one  per  cent,  solution  of  bichromate  of 
potash,  and  are  hence  removed  to  a  one-sixth  per  cent,  chro- 
mic acid  solution  for  one  or  two  days.  After  this  time  the 
part  of  the  yolk  which  has  the  blastoderm  resting  on  it,  is  cut 
off  with  a  razor  and  laid  in  common  alcohol,  in  which  with  due 
precaution  the  vitelline  membrane  can  be  readily  stripped  off 
from  the  blastoderm.  The  subsequent  processes  are  the  same 
as  with  the  blastoderm  of  the  trout. 

If  eggs  in  the  different  stages  of  their  passage  through  the 
Fallopian  tube  have  been  obtained,  it  is  eas}^  to  make  out  in 
prepared  sections,  that,  during  the  formation  of  the  cleavage- 
cavit}-,  the  large  coarse^  granular  elements  (filled  with  the 
coarse  granules  of  the  yolk)  which  compose  the  deeper  la}'ers 
of  the  blastoderm,  remain  lying  in  large  numbers  upon  the 
floor  of  the  cleavage-cavity;  that  these  are  most  numerous 
towards  the  area  opaca,  that  is,  where  the  peripheral  part  of 
the  blastoderm  lies  upon  the  white  yolk  (yolk-rim,  Keimwall) 
and  that  they  here  become  continuous  with  the  large  coarsely 
granular  elements  of  the  deeper  laj'ers  of  the  blastoderm. 
These  elements  lying  on  the  floor  of  the  cavity  and  derived 
from  the  blastoderm  during  the  formation  of  the  cavity,  corre- 
spond to  the  formative  elements  on  the  floor  of  the  cleavage- 
cavity  of  the  trout's  egg,  and  those  elements  which,  in  the 
batrachian  egg,  stretch  up  from  the  floor  of  the  cavity  to  the 
under  surface  of  the  dome  (see  fig.  175). 

Lamellae  of  the  Blastoderm  of  the  Chick. — The  study 
of  the  layers  of  the  embryo  of  the  chick  must  be  commenced 
with  fresh  laid  eggs.  The  egg  is  held  with  its  long  axis  hori- 
zontal ;  the  shell  is  cracked  at  its  upper  pole  ;  the  bits  of  shell 
in  this  place  are  removed  with  a  forceps,  and  the  outer  mem- 
brane torn  off  the  exposed  part ;  the  shell  is  then  broken  in 
two,  and  the  contents  are  let  out  into  a  flat  capsule.  With 
the  aid  of  scissors  and  forceps,  the  egg  (using  the  word  in  its 
more  restricted  sense)  is  freed  from  the  investing  albumen, 
which  is  carefully  poured  off.  After  having,  by  means  of  a 
lens,  acquired  a  general  notion  of  the  grosser  anatomical  re- 
lations as  they  present  themselves  on  a  surface  view  (such  as 
the  Area  pellucida,  A.  opaca,  Pander's  "  nucleus  of  the  white 
yolk,"  etc.),  we  pour  into  the  capsule  in  which  the  egg  lies  a 


1GG  EMBRYOLOGY. 

small  quantity  of  one  per  cent,  solution  of  bichromate  of  pot- 
ash, which,  after  one  or  two  days,  is  replaced  by  from  one-sixth 
to  one-tenth  per  cent,  chromic  acid  solution.  In  two  or  three 
days  more,  the  segment  of  yolk  which  hears  the  blastoderm  is 
cut  off  and  transferred  to  spirit ;  the  vitelline  membrane  is 
then  carefully  removed.  Afterwards  the  object,  which  may  or 
may  not  be  stained,  is  treated  with  absolute  alcohol,  embedded, 
and  employed  for  sections  in  the  manner  above  described. 
This  method  may  be  employed  during  the  first  twenty-four 
hours  of  incubation.  At  a  later  period,  or  at  all  events  after 
thirty-six  hours,  the  egg  must  be  treated  in  the  following 
manner  : — 

After  the  yolk  is  freed  from  albumen,  the  vitelline  mem- 
brane is  snipped  with  scissors  at  a  point  in  its  periphery  as 
far  removed  from  the  blastoderm  as  possible;  part  of  the  yolk 
flows  out  through  the  opening,  while  the  blastoderm  adhering 
to  the  vitelline  membrane  remains  in  position.  The  vitelline 
membrane  is  then  cut  around  the  blastoderm,  the  circular 
piece  not  only  including  the  blastoderm,  but  the  vitelline  mem- 
brane over  it,  together  with  a  portion  of  yolk  under  it.  This 
is  placed  in  a  small  flat  watch-glass,  which  is  held  by  forceps, 
and  is  brought  into  a  glass  capsule  containing  a  very  weak 
solution  of  bichromate  of  potash.  After  from  ten  to  fifteen 
minutes,  the  edge  of  the  vitelline  membrane  is  seized  by  for- 
ceps, and  gently  swayed  to  and  fro  in  the  liquid  till  that  mem- 
brane is  loosened  and  removed.  The  blastoderm,  with  the 
yolk  adhering  to  its  area  pellucida,  is  thus  completely  iso- 
lated. 

In  the  superficial  portion  of  the  germ  disks  thus  isolated, 
especially  those  of  the  early  part  of  the  second  day  of  incuba- 
tion (provided  that  they  are  normally  developed  as  is  usually 
the  case  in  spring  and  summer),  the  primitive  streak,  the  rudi- 
ments of  the  central  nervous  sj'stem,  of  the  chorda  dorsalis,  of 
the  proto vertebrae,  of  the  heart  and  great  vessels,  of  the  eyes, 
of  the  auditory  vesicles,  and  of  the  olfactory  pits,  may  be  ob- 
served. For  this  purpose,  the  blastoderm  is  floated  from  the 
watch-glass  on  to  an  object-glass,  and  examined  with  a  low 
power.  For  studying  the  first  vessels  it  is  necessaiy  to  use 
higher  powers.  The  object,  in  solution  of  bichromate  of  potash, 
or  in  a  mixture  of  this  and  glycerin,  should  be  surrounded  by 
a  ring  of  zinc  foil,  wax  mass,  putty,  or  sealing  wax,  and 
covered.  The  whole  germ  disk  of  the  second  day  of  incuba- 
tion, which  is  very  suitable  for  the  demonstration  superficially 
of  the  rudiments  of  the  organs  just  named,  may  be  preserved 
for  a  considerable  time,  if  the  wall  of  sealing-wax  surrounding 
the  blastoderm  is  high  enough.  The  mixture  consists  of  one 
part  of  one-sixth  per  cent,  chromic  acid,  two  parts  of  one-half 


BY   DR.    KLEIN.  167 

per  cent,  bichromate  of  potash,  and  one  part  glycerin.  The 
cover-glass  is  fixed  by  means  of  sealing-wax. 

Sections  through  the  nnincubated  germ-disk  show  that  it 
consists  of  two  layers,  besides  the  formative  elements  which 
are  to  be  found  on  the  floor  of  the  cleavage-cavity,  and  at  the 
yolk-rim.  (See  fig.  176.)  Sections  made  during  the  first  half 
of  the  first  day  teach  that  these  formative  elements  find  their 
way  from  the  yolk-rim  in  between  the  two  la3?ers  of  the  germ, 
so  as  to  form,  first  (seventeenth  hour),  the  central  part  of  the 
middle  layer  of  the  area  pellucida,  and  afterwards  (at  the 
twenty-third  or  twenty-fourth  hour),  the  remaining  portion  of 
that  layer.  Thus,  at  the  end  of  the  first  day,  the  germ-disk, 
which  before  consisted  of  two  layers,  consists  in  the  area  jjellu- 
cida  of  three — upper,  lower,  and  middle — the  last  originating 
from  the  formative  elements  which  had  previously  rested  on 
the  floor  of  the  cleavage-cavity.1 

As  the  central  nervous  system  is  developed  from  the  central 
portion  of  the  upper  layer,  the  remainder  of  this  layer  giving 
rise  to  the  epithelium  of  the  skin  and  of  the  cutaneous  glands, 
it  follows  that  the  upper  layer  in  the  chick  represents  the  upper 
and  nervous  layers  in  fish  and  Batrachia  ;  it  is  therefore  simply 
called  corneal  la3'er:  the  middle  layer  in  the  chick  corresponds 
to  the  third  in  the  trout  and  in  Batrachia,  and  is  therefore 
termed  motor-germinative  ;  the  lowest  la}rer  in  the  chick  cor- 
responds to  the  fourth  in  the  germ  of  trout  and  Batrachia,  and 
is  termed  the  epithelial  glandular  layer. 

AVhen  the  central  part  of  the  middle  germinal  layer  is  formed 
(seventeenth  hour),  the  upper  one  is  seen  to  be  thickened  at  its 
middle  portion  ;  it  consists  of  cylindrical  cells.  At  the  same 
time,  this  middle  portion  of  the  upper  layer  is  more  or  less 
fused  with  the  just  deposited  central  part  of  the  middle  layer. 
This  condition  shows  on  a  surface  view  the  primitive  streak 
(Axenstrang).  Along  with  the  formation  of  the  primitive 
streak,  the  dorsal  groove  is  also  developed,  a  differentiation  of 
the  middle  layer  of  the  germ  takes  place  into  the  notochord 
and  protovertebroe,  and  the  dorsal  laminae  begin  to  project. 
In  the  first  hours  of  the  second  day  of  incubation,  the  dorsal 
lamina;  are  seen  to  be  already  approaching  one  another,  so  that 
in  the  region  of  the  neck  they  almost  touch ;  at  the  tail  end 
they  are  still  a  considerable  distance  apart,  so  that  the  dorsal 
furrow  is  very  shallow.  A  short  time  afterwards,  the  dorsal 
lamina?  in  the  cervical  region  are  observed  to  be  completely 
closed,  and  the  dorsal  furrow  is  changed  into  a  canal — the  cen- 
tral canal  of  the  central  nervous  system.     (Figs.  117,  178.) 

In  sections  made  later  in  the  second  day  of  incubation,  the 

1  The  corneal,  motor-germinative,  and  epithelial  glandular  layers  cor- 
respond  to  the  epiblast,  mesoblast,  and  hypoblast  of  Huxley. — En. 


168  EMBRYOLOGY. 

rudiments  of  the  notochord  and  of  the  protovertebrrc  appear  in 
the  central  part  of  the  middle  layer  of  the  germ  ;  the  two 
outer  portions  of  this  same  layer — the  ventral  laminae  (Seiten- 
platten) — split  into  an  upper  parietal  (Hautmuskelplatte)  and 
a  lower  visceral  lamella  (Darmfaserplallc)  ;  between  the  cleft 
or  split  thus  formed  is  the  rudiment  of  the  pleuro-peritoneal 
cavity.     (Figs.  180-182.) 

At  the  same  time,  the  rudiment  of  the  Wollfian  duct  ap- 
pears on  the  upper  surface  of  the  middle  laj-er  of  the  germ, 
where  the  rudiments  of  the  protovertebrae  abut  on  the  ventral 
laminae.  In  sections  through  the  blastoderm  made  during  the 
second  day  (3G-48  hours),  the  protrusion  of  the  primary  optic 
vesicles  out  of  the  anterior  cerebral  vesicles  may  be  studied  as 
well  as  the  intrusion  of  the  secondary  eye  vesicle  into  the 
primary  (see  fig.  185  b),  which  proceeds  simultaneously  with 
the  formation  of  the  rudiment  of  the  lens  by  the  thickening 
and  subsequent  separation  by  constriction  of  the  intruded 
part  of  the  corneal  laj'er.  Similarly  the  auditory  vesicle  pre- 
sents itself  as  a  pit-like  depression  of  the  same  layer  ;  this  pit 
gradually  deepens  whilst  the  margins  rise  up  and  grow  until 
they  fuse  into  one  another,  so  as  to  form  the  auditory  vesicles. 
We  may  further  notice  the  extrusion  of  the  visceral  lamella  in 
the  region  of  the  neck,  which  forms  the  wall  of  the  heart  vesi- 
cle. Sections  made  on  the  second  and  the  commencement  of 
the  third  day  serve  for  the  study  of  the  development  of  the 
amnion,  as  a  fold-like  elevation  of  the  corneal  and  parietal 
Layers,  as  well  as  that  of  the  intestinal  groove,  and  of  the 
fovea  cardiaca  (  Vorderdarm)  by  the  closing  in  of  the  epithelial 
glandular  la}Ter  (.see  fig.  181).  The  extrusion  of  the  two  pri- 
mary hepatic  ducts  out  of  the  tube  so  formed,  its  partition 
into  a  posterior  oesophageal  and  an  anterior  tracheal-tube,  and 
the  extrusion  of  the  lungs  from  the  latter  must  be  followed  at 
later  stages  of  incubation. 


BY    DR.    KLEIN.  169 


CHAPTER  XIV. 

(appendix.) 
STUDY  OF  INFLAMED  TISSUES. 

Inflammation  of  Epithelium.—  The  inflammatory 
changes  of  the  epithelial  elements  of  the  cornea  may  be 
studied  03-  abrading  the  epithelium  over  a  limited  surface  in 
several  frogs,  and  examining  the  organ  at  various  periods  after 
the  injury.  The  cornea  must  be  studied  in  the  fresh  state 
(with  and  without  irrigation  with  serum),  as  well  as  after  pre- 
paration with  gold  and  hardening  in  alcohol.  Sections  in  both 
directions  must  be  made  of  the  preparations  so  obtained. 
Evidence  is  thus  obtained  (1)  of  the  division  of  the  nuclei  of 
the  epithelial  cells,  (2)  of  the  overgrowth  of  the  bodies  of  the 
cells,  and  (3)  of  their  subsequent  division. 

The  examination  of  the  catarrhal  secretions  of  any  inflamed 
mucous  membrane  which  is  covered  with  pavement  epithelium, 
is  very  instructive.  If  a  small  drop  taken  from  the  surface  of 
such  a  membrane  is  examined,  either  without  any  addition,  or 
diluted  with  a  drop  of  serum,  it  is  seen  that  among  a  great 
number  of  amoeboid  young  cells  (pus  cells)  a  few  larger  struc- 
tures are  to  be  found,  consisting  of  granular  protoplasm, 
which,  as  regards  their  form  and  size,  and  the  characters  of 
their  nuclei,  resemble  epithelial  cells.  Some  of  them  contain 
vacuoles  of  very  various  size,  each  exhibiting  in  its  wall  a  well- 
defined  nucleus,  which  either  shows  constrictions  or  is  already 
divided.  In  those  vacuoles  which  are  largest  there  are  pus- 
corpuscles.  Besides  these,  thin-walled  vesicular  bodies  are 
seen,  of  great  size,  filled  with  pus-corpuscles ;  and  between 
them  and  the  cells  containing  vacuoles  there  are  all  transitions. 
If  vertical  sections  are  made  of  a  bit  of  the  inflamed  mucous 
membrane  after  treatment  with  gold,  it  is  learnt  that  these 
structures  correspond  to  the  cells  of  the  superficial  layers.  In 
fresh  preparations  taken  in  such  a  wa}r  as  to  include  the  ele- 
ments of  deeper  layers,  large  epithelial  cells  are  seen  which 
exhibit  very  distinct  indications  of  division  both  in  their 
bodies  and  nuclei.  On  the  warm  stage  these  cells  may  be 
seen  actually  dividing.  To  obtain  permanent  preparations, 
the  fresh  inflamed  mucous  membrane  must  be  placed  in  two 
per  cent,  solution  of  bichromate  of  potash.  After  two  or 
three  days,  sections  may  be  made  by  shaving  off  a  portion  of 


170  STUDY    OF    INFLAMED    TISSUES. 

the  mucous  membrane,  and  comminuting  it  in  a  drop  of 
glycerin  with  a  blunt  instrument.  It  need  scarcely  be  added, 
that  both  those  cells  of  the  deeper  layers  which  are  in  the 
natural  state,  and  those  which  exhibit  appearances  of  division, 
have  the  ridged  character.  Similar  changes  can  be  studied  in 
certain  chronic  diseases  of  the  skin,  as  in  acuminated  condy- 
lomata.    (See  Chap.  II.) 

Inflammation  of  Endothelium. — As  regards  the  endo- 
thelium of  the  serous  membrane,  the  changes  consequent  on 
inflammation  have  been  already  referred  to.  In  the  blood- 
vessels, the  inflammatory  changes  may  he  studied  by  cauter- 
izing the  external  surface  of  any  superficial  vein  (e.g.,  the  ex- 
ternal jugular  or  femoral),  or  even  by  simply  ligaturing  the 
vessel.  Three  or  four  days  after  the  injury,  the  vessel  is  ex- 
cised and  hardened  in  chromic  acid,  or  treated  with  gold  and 
hardened  in  alcohol,  for  the  preparation  of  sections.  When 
the  vessel  is  very  thin-walled,  it  can  be  studied  at  once,  with- 
out preparation,  after  straining  with  gold  or  silver.  The 
appearances  correspond  to  those  observed  in  the  serous  mem- 
branes. 

Inflammation  of  Cartilage. — Germination  of  the  cells 
of  hyaline  cartilage  can  be  studied  after  mechanical  injury  of 
articular  cartilages.  The  best  method  is  to  pass  a  needle  into 
the  knee-joint  of  a  rabbit,  in  such  a  way  that  it  penetrates  into 
the  tibia.  A  few  days  after,  sections  are  made  of  the  fresh 
cartilage,  and  stained  in  gold.  It  is  more  difficult  to  observe 
inflammatory  changes  of  the  cartilage  cells  in  the  frog.  Much 
can  be  learnt  from  cartilages  of  human  joints  in  a  state  of 
chronic  inflammation. 

Inflammation  of  Bone. — Germination  of  the  cells  of  bone 
may  be  induced  in  the  long  bones  of  mammalia  by  passing  a 
red-hot  needle  as  deeply  as  possible  into  a  bone,  previously 
freed  of  the  soft  parts  covering  it,  and  then  cauterizing  the 
hole  with  a  pointed  stick  of  nitrate  of  silver,  or  by  violent 
fracture.  After  a  week  or  more  the  bone  is  excised.  Scale- 
like bits  are  then  split  off  from  the  immediate  neighborhood  of 
the  injury,  and  steeped  in  chloride  of  gold,  and  then  placed  in 
water  acidulated  with  acetic  acid  till  the}'  are  soft  enough  to 
render  it  possible  to  make  sections,  which  must  be  prepared 
in  glycerin.  Another  plan  is  to  place  the  part  in  solution  of 
chromic  acid  (§-  to  £  per  cent.),  to  which  hydrochloric  acid  has 
been  added,  as  described  fully  in  Chap.  II.  The  sections 
should  be  so  made  as  to  comprise  the  transition  between  in- 
flamed and  normal  conditions.  Human  inflamed  bones  can 
often  be  studied  in  amputated  limbs.  In  all  of  these  cases  the 
lacunne  are  seen  to  contain  groups  of  young  cells,  instead  of 
the  ordinary  branched  cells. 


BY    DR.    KLEIN.  171 

Inflammatory  Changes  in  the  Liver  Cells. — Inflam- 
mation of  the  tissues  of  the  liver  may  be  induced  by  passing 
a  needle  into  the  organ.  Twenty-four  to  forty-eight  hours 
after  the  injury,  the  animal  must  be  killed.  The  liver  cells 
exhibit  distinct  appearances  of  division  and  germination. 
Similar  appearances  are  seen  in  the  neighborhood  of  the  so- 
called  psorosperm  nodules  in  the  liver  of  the  rabbit. 

Inflammation  of  the  Cornea. — Inflammation  of  the 
cornea  may  be  studied  in  the  frog  in  two  ways  :  The  cornea 
may  be  cauterized  at  the  centre,  to  such  a  depth  as  almost  to 
perforate  it,  or  a  thread  may  be  drawn  through  it  entering  at 
the  centre  and  passing  out  through  the  sclerotic,  be3Tond  the 
margin,  the  ends  of  which  are  then  tied.  After  cauterization 
it  is  necessary  to  wash  the  part  with  a  few  drops  of  solution 
of  common  salt.  In  either  case  the  animal  is  placed  in  a 
beaker  glass,  with  some  moist  blotting-paper  at  the  bottom  of 
it.  To  study  the  successive  stages  of  the  process,  half  a  dozen 
corneas  should  be  prepared  in  this  way  at  a  time,  which  can 
then  be  excised  after  8,  12, 18,  24,  36,  and  48  hours.  The  best 
preparations  are  obtained  from  rana  esculenta,  during  the 
summer  months,  from  8  to  24  hours  after  the  introduction  of 
a  silk  thread,  as  above  described.  The  cornea  should  be 
studied  first  in  the  fresh  state,  and  then  stained  with  gold. 
It  is  excised  in  the  manner  directed  in  Chapter  II.  and  pre- 
pared in  humor  aqueus,  care  being  taken  to  protect  it  from 
pressure  by  inserting  slips  of  fine  paper  under  the  edges  of  the 
cover-glass.  The  contrast  between  a  cornea  twelve  hours  after 
injury  and  a  normal  one  lies,  first,  in  the  immense  number  of 
migrating  cells  it  contains,  and,  secondly,  in  the  marked  dis- 
tinctness of  the  branched  corpuscles.  The  migrating  cells  are 
most  numerous  towards  the  periphery,  occurring  more  and 
more  scantihr  towards  the  centre.  They  are  masses  of  proto- 
plasm of  irregular  form,  beset  with  knob-like  prominences, 
and  exhibit  very  active  amoeboid  movement.  To  study  their 
changes,  the  preparation  must  be  irrigated  with  serum.  For 
this  purpose,  a  frog  is  decapitated  and  the  blood  received  in 
a  porcelain  capsule  and  allowed  to  coagulate.  The  serum  is 
collected  in  capillary  glass  tubes.  The  irrigation  is  performed 
as  before  directed  (Chapter  I.),  a  very  small  strip  of  blotting- 
paper  being  used.  Under  the  immersion  objective,  the  most 
active  motions  can  then  be  observed;  and  if  a  single  corpuscle 
is  kept  under  observation  for  a  length  of  time,  it  is  sometimes 
possible  to  make  out  an  appearance  as  if  it  were  about  to  di- 
vide. A  line  presents  itself  on  the  surface,  which  after  a  time 
assumes  the  character  of  a  furrow.  Occasionally  the  furrow 
is  seen  to  deepen  till  the  two  parts  are  severed.  In  other 
cases,  one  of  the  knob-like  prominences  enlarges  and  separates 
itself.     As  regards  the  branched  cells,  some  of  them  appear 


172  STUDY    OF    INFLAMED    TISSUES. 

to  be  larger  than  natural,  while  their  processes  become  thicker 
and  less  branched.  Immediately  under  the  epithelium,  as  well 
as  under  the  endothelium  of  the  posterior  surface,  the  pro- 
cesses often  exhibit  node-like  enlargements.  Occasionally 
corpuscles  occur  which  possess  processes  only  on  one  side, 
while  on  the  other  they  merely  exhibit  slight  prominences.  If 
a  cornea  of  this  kind  is  immersed  in  solution  of  chloride  of 
gold  for  twenty  minutes  and  treated  as  usual,  the  corpuscles 
are  seen  to  be  much  more  stained  in  certain  parts  than  in 
normal  corneas,  although  the  latter  may  have  been  immersed 
twice  as  long.  If  a  comparison  is  made  between  different 
parts,  it  is  easy  to  satisfy  one's  self,  that  the  strongly  colored 
corpuscles  are  larger  and  look  as  if  they  were  swollen,  and 
that  their  processes  are  fewer  in  number  and  thicker.  The 
nuclei  of  these  corpuscles  exhibit  the  most  various  phases; 
constrictions  and  bulgings  are  seen  in  some,  complete  division 
in  others. 

This  is  by  no  means  the  final  stage  of  the  alteration  of  the 
corpuscles.  It  may  be  demonstrated  at  a  later  period  that  in 
some  parts  no  branched  corpuscles  can  be  distinguished,  their 
place  being  taken  by  a  trellis-work  of  spindle-shaped  cells, 
presenting  the  aspect  of  parallel  streaks  of  granular  protoplasm, 
running  in  two  directions  at  right  angles  to  each  other.  In 
each  streak  there  are  thickenings  at  intervals.  Each  thicken- 
ing ma}'  contain  either  a  few  deeply  stained  small  nuclei,  re- 
sembling those  of  the  neighboring  migratory  cells,  or  nuclei 
with  constrictions  which  resemble  those  which  are  character- 
istic of  the  cornea  corpuscles.  Between  these  larger  swellings 
containing  nuclei,  the  streaks  are  beset  with  small  nodosities 
of  various  sizes.  If  these  streaky  parts  are  compared  with 
others,  it  is  seen  that  there  are  all  transitions  between  the 
streaks  and  regularly  branched  oblong  cornea  corpuscles,  while 
in  other  directions  their  relation  can  be  traced  with  chains  of 
young  cells,  which  run  in  the  same  direction  as  the  streaks. 

The  entrance  of  migratory  cells,  and  even  a  beginning  of 
the  changes  above  described  in  the  cornea  corpuscles,  may  be 
imitated  in  an  excised  healthy  cornea,  as  follows  :  Inflammation 
is  produced  in  one  eye  by  cauterization,  and  then,  twenty-four 
hours  after,  a  portion  of  the  cornea  of  the  other  eye  is  excised, 
spread  out  carefull}',  and  lodged  between  the  membrana  nic- 
titans  and  the  cornea  of  the  injured  eye.  The  membrana  nic- 
titans  is  then  drawn  up  and  secured  by  two  or  three  ligatures 
to  the  skin.  After  twentj'-four  hours  more,  the  sac  is  opened 
and  the  cornea  taken  out.  It  may  be  examined  in  the  fresh 
state,  and  after  preparation  with  gold. 

Corneas  prepared  in  other  ways  (e.  </.,  by  gentle  friction  with 
solid  caustic,  as  directed  in  Chapter  II.,  or  by  holding  the 
head  over  hot  water,  and  brushing  the  surface  with  a  camel- 


BY    DR.    KLEIN.  173 

hair  pencil)  and  then  excised  and  stained  in  silver  solution, 
may  be  placed,  in  the  manner  above  described,  in  an  inflamed 
conjunctiva.  If  the  preparation  is  taken  out  after  twenty-four 
hours,  and  studied  immediately  on  the  warm  stage,  we  are  able 
to  satisfy  ourselves  that,  in  those  parts  which  exhibit  the  char- 
acteristic silver  staining,  3'oung  cells  are  actually  found  in  the 
canaliculi,  and  pass  along  them. 

Of  mammalia,  young  rabbits  answer  best  for  studies  of  the 
cornea.  Inflammation  is  excited  by  the  same  methods.  The 
results  are  also  similar.  In  a  cornea  excised  twenty-four  hours 
after  thorough  cauterization,. and  stained  with  gold,  parts  are 
found  in  the  strips  which  are  obtained  by  the  method  previously 
described,  in  which  the  canaliculi  assume  the  character  of 
channels  of  even  width,  which,  as  well  as  the  cell  cavities,  are 
lined  with  chains  of  small  cells,  arranged  in  linear  series,  so 
as  to  resemble  endothelial  elements.  From  these  appearances, 
we  are  justified  in  concluding  that  both  the  bodies  and  the  pro- 
cesses of  the  cornea  corpuscles  have  split  into  young  elements, 
changing,  at  the  same  time,  their  form. 

Inflammation  of  the  Tongue  of  the  Frog. — In  the 
tongue,  cell  division  can  be  studied  both  in  the  corpuscles 
peculiar  to  the  organ  and  in  migratory  cells.  For  this  purpose, 
the  tongue  is  prepared  as  for  the  study  of  the  circulation.  The 
mucous  membrane  covering  the  large  lymphatic  sac  of  the  under 
surface  is  snipped  off  with  curved  scissors.  The  observation 
is  necessarily  tedious,  often  lasting  for  forty-eight  hours.  It 
is  therefore  desirable  to  replace  the  tongue  in  the  mouth  for  a 
time  after  each  examination. 

Inflammatory  Changes  in  the  Tadpole's  Tail. — The 
inflammatory  changes  which  take  place  in  branched  cells  may 
be  studied  in  those  of  the  tadpole's  tail.  In  a  curarized  tad- 
pole, the  required  degree  of  irritation  can  be  produced  either 
by  simply  pencilling  the  surface,  or  by  allowing  a  drop  of  am- 
monia to  fall  on  it  from  a  capillary  pipette,  or,  finally,  by  piercing 
it  witli  a  needle.  The  research  must  be  continued  often  for 
many  hours.  The  results  are  similar  to  those  observed  in  the 
cornea,  and  may  be  studied  either  in  the  fresh  state  or  in  gold 
preparations. 


PHYSIOLOGY. 

PART  I.-BLOOD,  CIRCULATION,  RESPIRATION,  AND 
ANIMAL  HEAT. 


By  Dr.  BURDON-S ANDERSON. 


CHAPTER  XV. 

THE  BLOOD. 

Section  I.— The  Liquor  Sanguinis,  or  Plasma. 

The  blood  is  not  a  liquid,  in  the  strict  sense,  but  consists 
of  colored  and  colorless  corpuscles  suspended  in  liquor  san- 
guinis. It  is  necessary,  in  order  to  examine  the  liquor  san- 
guinis, to  separate  the  corpuscles  from  it  by  mechanical  meth- 
ods— i.  e.,  by  subsidence  and  decantation,  or  filtration.  As, 
however,  it  is  not  possible,  under  ordinary  circumstances,  to 
remove  blood  from  the  body  without  its  undergoing  that  re- 
markable change  which  we  call  coagulation,  neither  of  these 
methods  can  be  applied  to  the  blood  unless  by  some  means  or 
other  it  can  be  kept  in  a  fluid  state  during  the  process  of  fil- 
tration. The  earliest  successful  attempt  to  accomplish  this 
was  made  by  Johannes  Muller.  His  experiment  consists  in 
allowing  a  frog  to  bleed  into  a  solution  of  sugar  (half  per 
cent.),  and  then  rapidly  filtering  the  mixture.  The  large  cor- 
puscles of  the  frog's  blood  are  retained,  and  the  liquid  passes 
transparent,  and  free  from  corpuscles.  After  a  time  it  solidi- 
fies to  a  trembling  jell}-,  which  eventually  contracts  into  a  clot 
surrounded  by  serum.  This  experiment  was,  for  a  long  period, 
the  only  proof  of  the  existence  in  the  blood  of  a  liquid  possess- 
ing the  properties  of  plasma — that  is,  of  the  fact  that  the  liq- 
uor sanguinis  solidifies  when  left  to  itself,  quite  independently 
of  the  corpuscles.  It  does  not,  however,  enable  us  to  study 
the  properties  of  this  liquid  completely,  because  in  Midler's 
filtrate  it  is  diluted  with  saccharine  solution. 


176  THE    BLOOD. 

1.  Filtration  of  the  Blood  of  the  Frog.— Of  three  test 
tubes  (Fig.  190),  each  capable  of  holding  about  two  drachma 
of  liquid,  No.  1  is  filled  to  about  one-fifth  of  its  depth  with  a 
solution  of  sulphate  of  soda  obtained  by  mixing  one  volume 
of  saturated  solution  with  one  of  distilled  water  ;  No.  2  con- 
tains about  half  a  drachm  of  half  per  cent,  solution  of  sugar; 
No.  3,  half  per  cent,  solution  of  chloride  of  sodium.  Several 
frogs  are  then  selected,  in  each  of  which  the  pericardium  is 
exposed  and  divided  as  directed  in  §  40,  and  a  snip  made  in 
the  ventricle  with  fine  scissors,  the  integument  having  been 
dried  with  filtering  paper  before  making  the  first  incision. 
The  blood  is  allowed  to  flow  into  No.  1  until  four  times  as 
much  blood  has  been  added  to  the  quantity  of  solution  as  the 
tube  previously  contained.  To  each  of  the  liquids  in  No.  2 
and  in  No.  3  an  equal  volume  of  blood  is  added.  Each  of  the 
liquids  is  gently  agitated  and  then  thrown  on  a  filter  made  of 
strong  close-fibred  paper  prepared  for  its  reception,  and  corre- 
spondingly numbered.  In  each  instance  we  obtain  a  clear  and 
colorless  filtrate,  the  whole  of  the  colored  part  of  the  blood, 
i.  e.,  the  corpuscles,  being  collected  on  the  filter.  The  three 
filtrates  have,  however,  different  characters.  From  filter  No. 
1  is  obtained  a  liquid  which  remains  fluid  at  ordinary  temper- 
atures, i.  e.,  provided  that  the  room  is  moderately  cool.  From 
filter  No.  2  we  have  a  liquid  which  coagulates  immediately. 
From  No.  3  a  liquid  which  coagulates  after  a  time :  its  coagu- 
lation will  be  much  accelerated  if  it  is  placed  in  a  bath,  at  a 
temperature  approaching  that  of  the  body. 

In  the  sulphate  of  soda  filtrate  the  appearance  of  a  clot  is 
postponed  indefiniteby.  It  is,  how-ever,  not  the  less  certain 
that  it  really  contains  the  immediate  principles  of  which  fibrin, 
the  material  of  the  gelatinous  mass  seen  in  the  other  tubes,  is 
formed.  This  may  be  demonstrated  by  diluting  the  liquid 
with  distilled  water.  If  the  original  solution  had  been  satu- 
rated, water  might  have  been  added  gradually  for  some  time 
without  producing  any  apparent  change.  In  the  present  in- 
stance, the  solution  employed  contains  one  part  of  saturated 
solution  to  one  of  distilled  water.  If  water  is  added  to  the 
mixture  in  the  proportion  of  one-fifth  of  its  volume,  it  is  suffi- 
cient to  render  it  coagulable,  whereas  six  or  seven  volumes 
would  have  been  required  if  the  solution  had  been  concen- 
trated. As,  therefore,  saturated  solution  of  sulphate  of  soda 
contains  fifty  per  cent,  of  the  crystalline  salt,  this  last  must, 
in  order  to  the  prevention  of  coagulation  at  ordinary  tempera- 
ture, be  present  in  a  proportion  of  not  much  less  than  five  per 
cent. 

In  these  experiments  it  has  been  shown  (1)  that  the  colored 
blood  corpuscles  of  the  frog  are  so  large  that  they  do  not  pass 
through  close  filtering  papers ;  (2)  that  in  the  filtrate,  even 


BY    DR.    BURDOX-SANDERSON.  177 

when  it  is  diluted  with  its  volume  of  solution  ot  sugar,  a 
gelatinous  clot  forms  immediately,  under  ordinary  tempera- 
tures ;  (3)  that  the  process  of  coagulation  is  held  in  check  by 
certain  neutral  salts,  and  in  particular  by  sulphate  of  soda. 
A  similar  influence  is  exercised  by  sulphate  of  magnesia, 
nitrate  of  soda,  borax,  and  some  other  neutral  salts. 

2.  Separation  of  the  Corpuscles  from  the  Liquor 
Sanguinis  or  Plasma  in  the  Blood  of  Mammalia,  by- 
Subsidence  and  Decantation. — It  is  not  possible  to  filter 
mammalian  blood  in  the  way  above  described ;  for  the  cor- 
puscles are  so  small  that  they  will  run  through  the  finest  filter- 
ing paper.  We  must,  therefore,  have  recourse  to  subsidence. 
The  difficulties  of  separating  the  liquor  sanguinis  from  the 
corpuscles  by  subsidence  depends  on  the  length  of  time  which 
the  corpuscles  take  to  settle,  as  compared  with  the  rapidity 
with  which  the  blood  coagulates.  In  consideration  of  both 
these  circumstances  we  select  the  blood  of  the  horse  as 
preferable  to  any  other.  In  horse-blood  the  specific  gravity 
of  the  globules  is  1105,  that  of  the  liquor  sanguinis  1027-1028 
(Hoppe-Seyler) :  the  difference  is  considerable,  and  somewhat 
greater  than  in  other  animals.  But  it  is  of  more  importance 
still  that  horse-blood  coagulates  more  slowly  than  that  of 
other  animals. 

If  blood  is  received  into  one  of  two  similar  jars  from  a 
bullock,  into  the  other  from  a  horse,  it  is  seen  that  after  an 
hour  or  two  both  have  coagulated  firmly.  In  the  former,  the 
clot  is  all  of  one  color ;  in  the  latter,  it  is  divided  by  a  tolera- 
bly defined  horizontal  line  into  an  upper  colorless,  and  a  lower 
deeply  colored,  part,  the  upper  being  a  little  more  than  half 
the  depth  of  the  other.  In  the  one  case  the  corpuscles  have 
had  time  to  descend  through  the  upper  stratum  of  liquid  before 
it  solidified,  whereas  in  the  other  their  descent  is  anticipated 
by  the  coagulation  of  the  plasma.  In  the  horse  this  appear- 
ance is  always  observed  when  the  blood  taken  from  a  blood- 
vessel is  allowed  to  stand.  In  other  animals,  and  particularly 
in  man,  it  occurs  onlj'  under  abnormal  conditions  (particularly 
inflammatory  fever).     It  is  spoken  of  as  the  "buffy  coat." 

In  the  experiment  above  described,  the  object  we  have  in 
view  has  not  been  attained.  The  corpuscles  have  subsided 
more  or  less  completely,  but  the  plasma  no  longer  exists  as 
such.  It  has  separated  into  clot  and  serum.  To  succeed, 
coagulation  must  not  only  be  delayed  but  prevented — for 
which  purpose  there  is  but  one  means  available,  i.  e.,  cold.  At 
the  temperature  of  freezing,  coagulation  is  indefinitely  post- 
poned. The  blood  must,  therefore,  as  it  flows  from  the 
animal,  be  subjected  to  this  temperature,  and  kept  under  its 
protective  influence.  For  this  purpose  a  cylindrical  vessel 
made  of  tinplate,  of  the  form  shown  in  Fig.  191,  is  used. 
12 


178  THE   BLOOD. 

This  vessel  is  not  only  surrounded  with  ice  externally,  hut 
contains  in  its  axis  a  smaller  cylinder,  closed  at  its  lower  end, 
which  is  also  filled  with  ice.  Between  the  external  surface  of 
the  smaller  cylinder  and  the  internal  surface  of  the  larger, 
there  is  an  interval  which  does  not  exceed  half  an  inch  in 
width,  so  that  the  whole  of  the  liquid  which  occupies  it  is  kept 
at  freezing  temperature.  In  the  course  of  two  hours  or  less 
the  blood  has  separated  into  two  layers,  of  which  the  lower 
contains  all  the  corpuscles.  The  upper  stratum  consists 
entirely  of  plasma — a  liquid  which,  in  its  general  aspect, 
resembles  ordinar}'  serum,  but  is  not  so  transparent.  The 
most  obvious  as  well  as  the  most  important  property  which  it 
possesses  is  that  of  coagulation.  So  long  as  it  is  kept  at  0°  C. 
it  remains  liquid  ;  but  if  the  temperature  is  allowed  to  rise 
even  a  few  degrees  above  freezing  point,  the  whole  mass  is 
converted  into  a  gelatinous  clot. 

3.  Experiments  Illustrative  of  the  Properties  of 
Plasma  and  Fibrin. — 1.  Transfer  some  of  the  plasma,  with 
the  aid  of  a  cooled  pipette,  to  a  small  narrow  test  glass, 
surrounded  with  ice  and  water  contained  in  a  small  beaker. 
As  the  ice  gradualh'  wastes,  the  liquid  becomes  gelatinous. 
The  surface  by  which  the  mass  adheres  to  the  glass  is  so 
extensive  as  compared  with  its  volume,  that  the  adhesion  is 
permanent.  Consequently,  if  the  tube  is  examined  after 
having  been  left  to  itself  for  several  hours,  it  is  found  that 
the  plasma  has  not  (as  in  other  cases  of  coagulation)  separated 
into  clot  and  serum,  but  that  it  appears  to  be  entirely  semi- 
transparent  and  gelatinous. 

2.  Another  quantity  of  plasma  is  allowed  to  coagulate  in  a 
wide  vessel.  At  first  the  process  seems  to  go  on  in  a  similar 
manner,  and  for  a  time  the  mass  adheres  to  the  sides  of  the 
vessel.  Afterwards,  as  it  contracts,  drops  of  serum  collect, 
first  on  the  surface,  then  between  the  clot  and  the  sides  of  the 
glass.  Soon  the  clot  detaches  itself  wholly  from  the  vessel,  at 
the  same  time  diminishing  in  volume.  Eventually  we  have  a 
clear  liquid  (serum)  in  which  an  opaque  white  cast  of  the 
beaker  floats.  As,  in  consequence  of  the  adhesion  of  the 
coagulum  to  the  sides,  contraction  is  more  resisted  in  the 
horizontal  direction  than  in  the  vertical ;  the  upper  surface 
always  becomes  more  or  less  concave. 

3.  Preparation  of  Fibrin. — a.  The  clot  from  2  is  removed 
from  the  liquid,  divided  into  small  fragments,  and  washed  with 
water  until  it  is  absolutely  colorless.  In  this  condition  it 
differs  strikingly  from  the  semi-transparent  gelatinous  mass 
which  is  obtained  in  1.  It  is  dense,  fibrous,  and  opaque,  and 
extreml}-  clastic.  b.  A  fresh  portion  of  plasma  is  briskly 
agitated  with  a  rod  of  whalebone  or  other  suitable  implement. 
In  this  case  the  fibrin  is  obtained  in  fine  fibres,  which  may  also 


BY  DR.  BURDON-S ANDERSON.  179 

be  rendered  white  by  washing.  In  a  the  fibrin  has  passed 
through  a  previous  condition  in  which  it  was  gelatinous.  In 
o  it  is  obtained  directly  in  the  fibrillated  state. 

4.  Some  plasma  is  diluted  with  one  hundred  times  its 
volume  of  ice-cold  water,  or  three-quarter  per  cent,  salt  solu- 
tion, and  allowed  to  stand.  After  twenty-four  hours,  it  will 
be  found  that  there  are  long  delicate  filaments  of  fibrin, .which 
stretch  across  the  mass  of  liquid  in  every  direction,  from  one 
side  to  the  other  of  the  vessel  in  which  it  is  contained.  These 
filaments,  the  extremities  of  which  adhere  to  the  glass  surface, 
are  in  the  highest  degree  elastic.  If  they  are  separated  from 
their  points  of  attachment,  they  shrivel  up  into  little  lumps  of 
fibrin.  If  these  again  be  drawn  out  into  lengths,  they  resume 
their  original  form  when  let  go,  as  completely  as  a  bit  of 
India-rubber  would  do. 

5.  The  fibrin  prepared  in  3  is  placed  in  water  containing  one 
per  thousand  of  hydrochloric  acid.  At  first  it  swells  out  into 
a  bulk}'  hyaline  mass.  If  it  is  then  placed  in  the  air  bath, 
and  kept  at  a  temperature  of  from  40°  to  60°  C,  it  wastes 
awa}-  at  a  rate  which  varies  according  to  the  temperature. 
In  undergoing  solution  the  fibrin  has  been  transformed  into 
another  albuminous  compound,  sj'ntonin  or  acid-albumin.1 
If  the  liquid  is  carefully  neutralized,  the  syntonin  is  precipi- 
tated, but  the  precipitate  is  redissolved  in  a  slight  excess  of 
alkali  or  alkaline  carbonate. 

6.  Another  portion  of  the  same  fibrin  is  soaked  in  solution 
of  peroxide  of  hydrogen.  It  is  then  placed  on  a  sheet  of  fil- 
tering paper,  which  has  been  previously  soaked  in  tincture  of 
guaiacum.  It  soon  becomes  surrounded  with  a  border  of  blue, 
in  consequence  of  the  oxidation  of  the  guaiacum.  Another 
method  consists  in  first  steeping  a  fragment  of  fibrin  in  alco- 
hol, then  in  tincture  of  guaiacum,  and  finally  immersing  it  in 
the  solution  of  the  peroxide:  the  fibrin  becomes  blue.  The 
same  thing  happens  if  the  fibrin  is  dipped  in  a  mixture  of  the 
tincture  and  the  solution.  This  reaction  signifies  simply  that 
fibrin  decomposes  peroxide  of  hydrogen:  it  affords  no  proof 
of  the  presence  of  ozone. 

4.  Experiments  relating  to  the  so-called  Fibrin 
Factors — Paraglobulin  and  Fibrinogen. — In  every  act 
of  coagulation,  fibrin  appears  to  be  produced  by  the  combina- 
tion of  two  albuminous  substances  closely  allied  as  regards 
their  chemical  characters,  both  of  which  are  to  be  found  in 
plasma  as  obtained  by  any  of  the  methods  above  described. 
Fifty  cubic  centimetres  or  thereabouts  of  the  plasma,  which 
has  been  kept  at  a  freezing  temperature,  are  added,  in  a  beaker, 

1  The  ending  in  is  adopted  here  and  elsewhere  to  denote  that  the 
word  is  used  in  a  stcechiological  sense.     Albumen  is  white  of  egg. 


180  THE  BLOOD. 

to  five  hundred  centimetres  of  distilled  water.  A  current  of 
carbonic  acid  gas  is  allowed  to  pass  through  the  liquid  until 
it  becomes  turbid;  much  froth  collects  on  the  surface.  On 
discontinuing  the  current,  it  is  found  that  a  distinctly  granular 
precipitate  has  been  formed.  This  is  paraglobulin.  After 
decanting  off  most  of  the  liquid,  the  precipitate  is  collected 
on  a  filter  and  washed  with  water  saturated  with  carbonic 
acid.  It  is  insoluble  in  water  which  has  been  boiled,  but 
soluble  in  water  containing  air  or  oxygen  ;  it  decomposes  per- 
oxide of  hydrogen  in  the  same  way  as  fibrin.  It  is  character- 
istic of  the  solution  that  when  mixed  with  a  solution  of  a  sub- 
stance to  be  spoken  of  immediately  under  the  name  of 
fibrinogen,  fibrin  is  produced.  This  property  is  denoted  by 
the  term  Jibrmoplastic,  which  is  applied  both  to  the  substance 
and  to  the  solution. 

2.  After  the  precipitate  has  had  time  to  subside,  the  clear 
liquid  is  decanted  off,  diluted  with  twice  its  own  bulk  of  ice- 
cold  water.  A  stream  of  carbonic  acid  gas  is  again  passed 
through  it.  At  first  it  remains  clear,  but  after  a  time  a  some- 
what viscid  scum  begins  to  collect  on  the  surface  of  the  liquid 
and  on  the  sides  and  bottom  of  the  glass.  This  precipitate  is 
fibronogen.  This  process  involves  an  immense  expenditure  of 
ice.  and  occupies  a  great  deal  of  time. 

3.  Fifty  cubic  centimetres  of  serum  of  ox-blood  are  mixed 
with  half  a  litre  of  distilled  water.  A  stream  of  carbonic  acid 
gas  is  passed  through  it  as  before.  A  granular  precipitate  is 
formed,  which,  like  that  obtained  from  plasma,  is  fibrino- 
plastic. 

4.  Fifty  cubic  centimetres  of  hydrocele  fluid  or  pericardial 
fluid  are  diluted  with  water  and  treated  with  carbonic  acid 
gas  as  before.  A  slimy  white  substance  is  formed  in  very 
small  quantity,  which  collects  on  the  surface  of  the  liquid  and 
on  that  of  the  glass. 

5.  The  granular  precipitates  in  1  and  3  may  be  obtained  in 
the  same  form  by  adding  to  the  same  diluted  liquids  acetic 
acid,  the  quantity  of  which  must  be  so  small  that  the  liquid 
still  retains  a  trace  of  alkalinity.  The  precipitate  has  the 
characters  described  in  1. 

6.  Twenty  cubic  centimetres  of  filtered  hydrocele  or  peri- 
cardial fluid  are  placed  in  a  beaker  in  the  air  bath  at  a  tem- 
perature of  40°  C.  The  liquid  does  not  coagulate,  but  on 
adding  serum  a  firm  clot  is  formed. 

7.  A  second  quantity  of  the  same  liquid  which  has  been 
ascertained  by  the  preceding  experiment  to  be  fibrinogenic, 
i.  e.,  to  have  the  property  of  coagulating  on  the  addition  of  a 
fibrinoplastic  liquid,  is  saturated  with  pure  chloride  of  sodium 
by  adding  the  salt  gradually  in  fine  powder.  As  the  point  of 
saturation  approaches,  the   previously  clear  liquid  becomes 


BY  DR.  BURDON-5 ANDERSON.        *    181 

cloudy,  and  on  standing,  a  flocculent  deposit  separates.  This 
deposit  is  fibrinogen.  It  must  be  collected  on  a  filter  and  well 
washed  with  saturated  solution  of  common  salt.  If  the  sub- 
stance so  prepared  is  dissolved  in  a  small  quantity  of  distilled 
water,  and  the  liquid  filtered,  a  clear  solution  of  fibrinogen 
and  chloride  of  sodium  is  obtained.  It  possesses  the  property 
of  coagulating  on  the  addition  of  serum,  especially  at  a  tem- 
perature approaching  that  of  the  body. 

8.  Filtered  serum  of  blood  treated  in  precisely  the  same  way 
yields  a  similar  product  containing  paraglobulin.  The  filtrate 
obtained  determines  coagulation  in  hydrocele  liquid  when 
added  to  it.  Coagulation  may  be  also  expected  to  occur  when 
the  fibrinoplastic  filtrate  obtained  in  8  is  added  to  the  fibrino- 
genic  filtrate  obtained  in  7.  The  result  of  this  experiment  is, 
however,  uncertain. 

9.  If  plasma  is  saturated  with  chloride  of  sodium  in  the 
manner  above  described,  a  precipitate  is  obtained  which  con- 
tains both  paraglobulin  and  fibrinogen.  If  this  is  washed  with 
saturated  solution  of  salt  as  before,  dissolved  in  distilled  water, 
and  rapidly  filtered,  a  clear  fluid  passes  through,  which  after  a 
while  coagulates,  and  which  has  the  characters  of  fibrin. 

10.  If  the  transudation  liquids  above  mentioned  cannot  be 
obtained,  a  liquid  may  be  prepared  by  adding  to  plasma  a  solu- 
tion of  a  neutral  salt,  such  as  sulphate  of  magnesia  or  sulphate 
of  soda,  so  as  to  prevent  coagulation.  If  the  quantity  of 
neutral  salt  added  is  just  sufficient  for  the  purpose,  the  addi- 
tion of  a  little  paraglobulin  at  once  determines  the  formation 
of  a  clot.  Blood  is  received  directly  from  the  circulation  into 
one-third  of  its  volume  of  ice-cold  saturated  solution  of  sulphate 
of  soda  or  of  sulphate  of  magnesia.  The  mixture  is  allowed  to 
stand  in  ice  till  next  day,  in  order  that  the  corpuscles  may  com- 
pletely or  in  great  measure  settle.  The  clear  liquid  (plasma 
and  neutral  salt  solution)  is  then  removed  hy  decantation  with 
a  capillary  syphon,  and  used  as  follows  :  a  A  small  quantity  is 
placed  in  an  eprouvette,  in  the  warm  chamber,  at  40°  C.  b 
Other  quantities  are  diluted  with  proportions  of  distilled  water, 
varying  from  4  parts  to  10  parts,  and  kept  at  the  ordinary  tem- 
perature, a  Coagulates  at  once.  Of  b  the  more  dilute  coagu- 
late spontaneously,  even  at  the  ordinary  temperature.  To 
those  that  do  not  so  coagulate,  paraglobulin  is  added,  when  it 
U  found  that  in  the  more  concentrated  quantities  the  addition 
determines  the  formation  of  a  clot.  Kuhue  recommends  for 
this  experiment  a  solution  of  sulphate  of  magnesia  containing 
1  part  of  the  salt  to  3£  of  water.  Plasma  mixed  with  this 
solution  in  the  proportion  of  '.>  parts  to  1,  and  then  diluted  with 
8  parts  of  water,  coagulates  on  the  addition  of  paraglobulin.' 

1  Lehrbuch  der  pbysiol.  Chemie,  p.  172. 


182  THE    BLOOD. 

11.  Diluted  plasma  which  has  been  treated  with  carbonic 
acid  gas  docs  not  coagulate,  even  when  Bhaken  with  air  and 

subjected  to  the  temperature  of  the  bod}-  (40°  C). 

From  the  above  experiments  we  learn  that  plasma  contains 
two  albuminous  compounds,  precipitable  by  carbonic  aeid  gas 
and  by  aeetic  aeid;  that  one  of  them  (paraglobulin)  exists 
alone  in  serum  in  considerable  quantity ;  that  the  other  (fibrin- 
ogen) exists  alone  in  liquids  effused  into  uninflamed  serous 
cavities  in  very  small  quantity;  that  when  paraglobulin  is 
added  to  these  effusion-liquids  they  become  coagulable,  justas 
serum  may  be  made  coagulable  by  the  addition  of  fibrinogen. 

5.  Heynsius's  Experiment.1 — From  the  properties  of 
blood  plasma  demonstrated  in  the  above  experiments,  we  are 
apt  to  infer  that  this  liquid  is  the  exclusive  source  of  the  fibrin 
formed  when  blood  coagulates.  There  is  reason,  however, for 
believing  that  a  very  considerable  quantity  of  fibrin-producing 
material  is  contained  while  the  blood  is  circulating,  in  the  col- 
ored or  colorless  corpuscles,  for  it  can  be  shown  that  if  these 
elements  arc  separated  as  complttelyas  possible  by  subsidence 
and  decantation  from  a  known  quantity  of  blood,  and  added 
to  a  similar  quantity  of  serum,  this  serum  acquires  the  pro- 
perty of  coagulating  ;  and  the  quantity  of  fibrin  produced  bears 
a  very  considerable  proportion  to  the  whole  quantity  which  the 
blood  would  have  yielded.  Fifty  cubic  centimetres  of  blood 
are  received  directly  from  the  vein  of  a  horse  or  ass  into  a 
measuring  tube  surrounded  with  ice.  The  blood  is  immediately 
afterwards  poured  into  a  tall  narrow  glass  cylinder,  which 
ahead}7  contains  half  a  litre  of  a  two  per  cent,  solution  of  com- 
mon salt,  previously  cooled  by  standing  in  ice.  In  this  vessel 
the  mixture  is  allowed  to  remain  until  the  corpuscles  have  sub- 
sided, after  which  the  liquid  must  be  drawn  off  with  the  aid  of 
a  capillary  pipette  or  syphon.  The  remainder  is  then  mixed 
with  a  similar  quantity  of  salt  solution,  again  left  to  itself  sur- 
rounded by  ice,  and  the  process  repeated.  Fifty  centimetres 
of  serum  of  ox  blood  previousl}-  prepared,  having  been  then 
added  to  the  corpuscles  which  remain  at  the  bottom  of  the 
vessel,  the  mixture  is  placed  in  water  at  a  temperature  of  40° 
C.  Alter  two  or  three  minutes  coagulation  takes  place.  The 
clot  is  collected  and  washed,  dried  and  weighed.  In  the  mean 
time  the  fibrin  yielded  by  an  equal  quantity  of  blood  is  deter- 
mined. On  comparing  the  weights,  it  is  found,  as  before  stated, 
that  the  coagulum  obtained  from  the  mixture  of  serum  and  cor- 
puscles alone,  is  nearly  equal  to  that  obtained  from  the  whole 
blood  (corpuscles  and  plasma).  It  has  been  further  shown  by 
Heynsius,  that  if  blood  is  received  in  an  ice-cold,  half  per  cent., 
or  one  per  cent.,  solution  of  common  salt,  the  quantity  of  fibrin 

1  Pfluger's  Archiv.  B.  III.  p.  419. 


BY    DR.    BURDON-SANDERSON.  183 

yielded  by  the  plasma  is  much  less  (so  to  speak)  than  it  ought 
to  be,  i.  e.,  much  less  than  that  yielded  b}r  a  corresponding 
quantity  of  blood.  This  fact,  taken  in  connection  with  the 
result  of  our  experiment,  leads  us  to  regard  it  as  probable  that 
in  circulating  blood,  the  liquor  sanguinis  contains  less  of  the 
fibrin  factors  than  it  does  immediately  after  its  removal  from 
the  body.  If  this  inference  is  correct,  there  can  be  little  doubt 
that  it  somehow  or  other,  in  leaving  the  living  vessel,  acquires 
fresh  properties  of  coagulation  from  its  formed  elements. 
Heynsius  believes  that  the  colored  blood  disks  are  alone  con- 
cerned in  this  action,  and  attributes  it  to  the  discharge  into 
the  plasma  of  certain  of  their  constituents.  His  results  are, 
however,  quite  as  consistent  with  the  belief  that  the  colorless 
elements  are  the  chief  agents,  in  favor  of  which  several  facts 
may  be  demonstrated.  Vaccine  and  blister  fluid  are  both  co- 
agulable  ;  they  contain  no  colored  blood  corpuscles, but  always 
many  colorless  corpuscles.  If  the  process  of  coagulation  is 
watched  in  either  of  these  liquids  under  the  microscope,  it  is 
seen,  not  merely  that  it  begins  from  these  elements,  but  that 
it  occurs  nowhere  in  the  liquid  excepting  where  they  are  pre- 
sent. Again,  if  a  ligature  is  drawn  through  a  vein  in  which 
blood  is  circulating,  as  e.  gr.,  through  the  external  jugular  of 
a  rabbit  or  guineapig,  and  allowed  to  remain  there  for  a  time, 
and  then  removed  and  examined  microscopically,  it  is  found 
that  the  threads  of  the  ligature  are  crowded,  and  its  surface 
encrusted,  with  colorless  corpuscles.  These  bodies  are  held 
together  by  fibrin,  which  appears  to  grow  from  their  surface 
into  the  blood-stream. 

iox  II. — Conditions  wnicn  Affect  the  Coagulation  of  the 
Blood. 

Although  the  circulating  blood  contains  either  in  its  colored 
corpuscles  or  plasma  both  the  fibrin  factors,  i.  e.,  the  imme- 
diate principles  necessary  for  its  coagulation,  it  does  not  co- 
agulate. In  other  words,  the  blood,  so  long  as  it  forms  part  of 
the  normal  living  body,  contains  no  fibrin.  This  remarkable 
fact  is  dependent  on  the  maintenance  in  the  corpuscles  of  those 
chemical  changes  which  constitute  their  life.  And  inasmuch 
as  these  changes  cannot  continue  in  the  absence  of  the  physical 
and  chemical  conditions  to  which  the  blood  is  subjected,  so 
long  as  it  is  contained  in  healthy  bloodvessels,  an}'  derange- 
ment of  those  conditions  leads  to  the  formation  of  a  clot.  It 
can  Ik:  proved  experimentally  (1)  That  blood  does  not  coagu- 
late in  the  living  heart  or  in  a  living  bloodvessel,  even  when 
tin;  circulation  is  arrested;  (2)  That  although  normal  blood 
ordinarily  coagulates  as  soon  as  it  is  withdrawn  from  the  body, 
there  are  certain  circumstances  under  which  the  act  of  coajni- 


184  TIIE    BLOOD. 

lation  cither  does  not  take  place,  or  is  accomplished  in  so  im- 
perfect a  manner,  that  the  clot  is  scarcely  recognizable  as 
such. 

6.  The  following  is  a  modification  of  an  experiment  of 
Briicke,  devised  by  my  friend  Dr.  Durante.  In  a  rabbit,  two 
small  incisions  are  made  across  the  course  of  the  external  jugu- 
lar vein,  (see  §  48)  one  near  the  clavicle,  the  other  near  t he 
origin  of  the  vessel — great  care  being  taken  not  to  go  deeper 
than  is  necessary  in  order  to  see  the  vessel  through  the  fascia. 
A  small  needle  is  then  passed  under  the  vein  near  the  proxi- 
mal incision,  in  a  direction  at  right  angles  to  that  of  its  axis, 
and  corresponding  to  that  of  the  incision,  but  deeper.  A 
second  needle  is  then  laid  in  the  course  of  the  incision,  and 
drawn  tightly  towards  the  first  by  a  ligature  at  either  end,  by 
which  means  the  blood  current  is  entirely  arrested,  while  the 
coats  of  the  vein  are  absolutely  protected  from  injury.  A 
second  pair  of  needles  is  then  inserted  at  the  distal  incision, 
and  secured  in  a  similar  manner,  so  as  to  shut  in  the  blood 
with  which  the  vein  becomes  distended  after  the  tightening  of 
the  first  ligature.  After  the  lapse  of  a  couple  of  days,  the 
ligatured  portion  of  the  vein  is  exposed  at  some  part  of  its 
course,  and  punctured  with  a  glass  pipette,  by  means  of  which 
the  blood  is  withdrawn  from  it  by  suction  in  a  perfectly  liquid 
state.  On  removing  the  needles  the  natural  circulation  is  at 
once  restored.  This  result,  however,  is  onh/  obtained  when  t  he- 
greatest  care  is  used  to  avoid  injury  to  the  coats  of  the  vein. 
This  may  be  readily  proved  by  repeating  the  experiment 
(which, in  a  practical  point  of  view,  is  of  great  importance)  in 
a  different  wa}r.  If,  instead  of  using  needles,  ordinary  liga- 
tures are  placed  on  the  points  indicated,  a  coagulum  is  formed, 
so  that  on  pinching  the  vein  no  blood  flows.  On  opening  such 
a  vessel  it  is  found  to  be  occupied  by  two  clots  (thrombi),  each 
of  which  is  thickest  and  firmest  at  the  ligature,  and  becomes 
thinner  and  looser  towards  the  middle  of  the  deligated  part. 
Dr.  Durante  has  shown  that,  in  this  experiment,  this  absence  of 
coagulation  depends  on  the  integrity  of  the  endothelium. 
Wherever  the  endothelium  of  a  vein  is  irritated  so  as  to 
undergo  germination,  a  clot  is  formed  which  is  co-extensive 
with  the  alteration  of  the  endothelial  elements. 

7.  The  arterial  trunks  leading  from  the  heart  of  a  frog  or 
tortoise  are  first  tied,  and  then  (as  soon  as  the  heart  has  be- 
come distended)  the  venous  trunks.  The  heart  full  of  blood 
is  removed  from  the  bod}-  and  suspended  in  a  small  flask  by 
one  of  the  ligatures.  The  flask  is  allowed  to  stand  so  long  as 
the  heart  continues  to  pulsate.  If,  then,  before  the  pulsations 
have  entirel}'  ceased,  the  blood  is  allowed  to  flow  from  the 
heart  by  removing  the  arterial  ligatures,  it  is  seen  to  be  fluid. 


BY    DR.    BURDON-SANDERSON.  185 

As  soon  as  it  escapes  it  coagulates.     This  is  also  an  experi- 
ment of  Briicke. 

8.  Recklinghausen's  Experiment. — A  small  porcelain 
crucible  is  heated  to  redness,  and  allowed  to  cool  without  re- 
moving the  cover.  The  pericardium  of  a  frog  is  then  exposed 
and  divided,  and  a  snip  made  in  the  ventricle  with  absolutely 
clean  scissors,  the  frog  being  held  in  such  a  position  that  the 
blood  discharged  from  the  wound  in  the  heart  may  be  received 
in  the  prepared  crucible  without  coming  in  contact  with  the  ex- 
ternal surface  of  the  body.  The  quantity  of  blood  used  should 
not  exceed  ten  drops.  The  crucible  (without  its  cover)  is  then 
placed  on  a  ground-glass  plate,  and  covered  with  a  wide  bell- 
glass,  the  edge  of  which  is  also  ground,  so  that  it  fits  the  glass 
plate  perfectly.  The  blood  coagulates  immediately,  but  during 
the  course  of  the  next  twenty-four  hours  it  apjjears  to  become 
liquid  again.  If  the  experiment  has  been  carefully  performed, 
the  blood  remains  unaltered  (its  colorless  corpuscles  retaining 
their  vital  activity)  for  many  daj's:  it  is,  however,  necessary 
to  renew  the  air  contained  in  the  bell-glass,  by  lifting  it  care- 
fully from  time  to  time.  This  experiment  may  be  also  made  writh 
mammalian  blood,  provided  that  a  temperature  is  maintained 
equal  to  that  of  the  body,  for  which  purpose  v.  Recklinghausen 
uses  an  air  bath  furnished  with  a  Bunsen's  regulator.  The 
capsule  is  heated  to  redness,  because,  if  it  were  not  so,  the  or- 
ganic matter  adherent  to  the  surface  of  the  porcelain  would 
determine  changes  in  the  blood,  which  would  be  fatal  to  the 
vitality  of  its  elements.  With  a  similar  view  every  possible 
precaution  is  used  against  other  modes  of  contamination, 
whether  from  the  air  or  from  surfaces  with  which  the  blood  is 
brought  into  contact.  The  liquefaction  of  the  coagulum  in  the 
preceding  experiment  is  onl}r  apparent.  To  prove  this,  the 
process  must  be  observed  microscopically  under  otherwise 
similar  conditions.  The  following  method,  suggested  by  cer- 
tain experiments  of  Schlarewski  (who,  however,  does  not  appear 
to  have  understood  their  significance),  I  owe  to  my  assistant, 
Mr.  Schafer.  Several  very  thin  walled  capillary  tubes,  not 
more  than  \  millimeter  in  diameter,  are  filled  with  blood  as  it 
flows  from  the  artery  of  a  frog,  and  at  once  placed  under  the 
No.  9  immersion  objective  of  Hartnack.  The  contents  of  the 
tube  can  be  seen  with  perfect  distinctness.  At  first  the  Avhole 
of  the  space  inclosed  in  the  tube  is  occupied  by  colored  blood 
disks.  After  a  few  minutes  it  is  seen  that  coagulation  has  oc- 
curred, and  that  the  cylindrical  mass  in  which  the  corpuscles 
arc  contained  is  separated  from  the  glass,  by  a  transparent 
border  in  which  there  are  no  corpuscles.  Next,  the  colorless 
corpuscles  begin  to  squeeze  themselves  out  of  the  coagulum 
and  swim  in  the  serum  (see  Fig.  H)2).  From  the  activity  of 
the  amoeboid  movements  which  these  corpuscles  exhibit  imme- 


186  THE    BLOOD. 

diately  after  their  expulsion,  the  observer  is  inclined  to  attri- 
bute their  escape  from  the  clot  to  these  movements  ;  this  notion 
is,  however,  proved  to  be  erroneous  by  what  follows.  In  a 
short  time  (usually  about  forty-five  minutes  after  the  com- 
mencement of  the  observation),  the  colored  corpuscles  begin 
to  participate  in  the  process,  and  escape  from  the  still  sharply- 
defined  edge  of  the  clot  in  such  numbers  that  the  liquid  becomes 
so  crowded  with  them,  that  microscopical  examination  is  no 
longer  possible.  If  now  the  tube  is  removed  from  the  stage 
and  placed  vertically,  it  is  seen,  after  a  time,  that  the  corpuscles 
subside  to  the  bottom  of  the  tube,  leaving  a  clear  space  con- 
taining serum  above.  Here,  then,  we  have  a  process  which  we 
might  at  first  sight  be  disposed  to  regard  as  a  resolution  of  the 
eoagulum  ;  the  appearance  is,  however,  deceptive,  for  if  the 
tube  is  discharged  into  a  watch-glass  and  examined  under  a 
low  power,  the  eoagulum  is  easihT  found  as  a  thin  cord  of  fibrin 
floating  in  the  liquid.  In  short,  the  whole  process  of  emigra- 
tion of  the  corpuscles  and  liquefaction,  of  the  clot  is  the  conse- 
quence of  the  contraction  of  a  reticulum  of  fibrin  of  such  extreme 
looseness,  that  it  is  incapable  of  retaining  the  corpuscles  in  its 
meshes. 

9.  The  two  experiments  last  related  prove,  as  regards  the 
blood  of  the  frog,  that,  under  certain  conditions,  coagulation 
occurs  very  imperfectly,  even  though  the  blood  be  removed 
from  the  body,  and  consequently  that  Briicke's  inference,  that 
the  circulating  blood  is  prevented  from  coagulating  by  the  in- 
fluence of  the  living  A'essel,  need  no  longer  be  maintained.  The 
following  experiment,  devised  by  Mr.  Schafer,  which  has  been 
repeated  a  great  number  of  times  in  the  laboratory  of  Univer- 
sity College,  proves  this  much  more  conclusively  and  satisfac- 
torily. A  glass  tube,  three  or  four  inches  long,  is  drawn  out 
atone  end  into  an  arterial  canula  of  the  usual  form  and  of 
suitable  size.  A  frog  having  been  secured  in  the  usual  way 
(see  §  46)  in  the  prone  position,  the  heart  is  exposed  and  the 
right  aorta  ligatured.  A  clip  is  then  placed  on  the  left  aorta 
at  its  origin  from  the  bulb.  The  canula  (Fig.  103,  a)  is  then 
inserted  and  secured  in  the  left  aorta,  and  the  tube  supported 
vertically  by  a  suitable  holder.  This  done,  and  the  clip  having 
been  removed,  the  blood  is  allowed  to  flow  into  the  tube.  It 
rises  to  a  height  which  varies  according  to  the  vigor  of  the 
animal  and  the  quantity  of  blood  which  its  vascular  sj'stem 
contains,  the  blood  column  oscillating  with  the  contractions  of 
the  heart.  If  now  the  tube  is  left  to  itself,  no  coagulation  takes 
place.  In  a  very  few  minutes  the  corpuscles  begin  to  subside, 
leaving  an  upper  layer  of  clear  liquid,  the  depth  of  which  gradu- 
ally increases.  If  it  is  removed  with  a  capillary  pipette  and 
submitted  to  examination,  it  is  found  to  possess  all  the  proper- 


BY    DR.    BURDON-SANDERSON.  187 

ties  which  are  characteristic  of  plasma.     It  contains  scarcely 
an}'  colored  but  a  considerable  number  of  colorless  corpuscles. 

Section  III. — The  Coloring  Matter. 

10.  Methods  by  which  the  Blood  can  be  rendered 
Transparent  or  Laky. — It  has  long  been  known  that, 
when  water  is  added  to  blood  in  quantity,  the  blood  corpuscles 
are  apparently  dissolved  in  the  diluted  liquor  sanguinis.  This 
solution  is,  however,  only  partial ;  for,  if  the  liquid  is  examined 
under  the  microscope,  each  corpuscle  is  seen  to  be  represented 
by  a  colorless  spheroidal  residue.  This  residue  was  formerly, 
described  as  the  membrane  of  the  corpuscle,  rather  in  con- 
formity to  the  notion  that,  being  a  cell,  it  must  have  a  mem- 
brane, than  because  the  structure  in  question  possessed  mem- 
branous characters.  We  now  recognize  it,  not  as  a  membrane, 
but  as  the  porous  structure  fully  described  in  the  histological 
part  as  the  cecoid. 

There  are  many  other  methods  by  which  the  zooid  may  be 
compelled  to  relinquish  its  dwelling  without  altering  the  den- 
sity of  the  serum  at  all.  So  long  ago  as  1851,  Dr.  De  Chaumont 
discovered  that  the  vapor  of  chloroform  had  this  effect.  That 
of  ether  acts  in  the  same  way,  but  not  so  rapidly.  More  re- 
cently, it  has  been  shown  by  Rollett  that  the  same  effects  are 
produced  by  freezing,  as  well  as  by  electrical  discharges  and 
induction  currents.  In  all  these  cases  (as  has  been  already 
seen  as  regards  some  of  them)  the  blood  undergoes  a  remark- 
able change  of  appearance.  In  the  natural  state,  blood,  even 
in  the  thinnest  layers,  is  opaque.  One  may  judge  of  this  by 
looking  at  it  either  by  transparent  light  (as,  e.  g.,  in  a  very 
thin  capillary  tube)  or  by  reflected  light,  spread  out  in  a  thin 
layer  over  the  surface  of  a  porcelain  capsule.  In  the  former 
case  the  blood  presents  the  appearance  of  a  solid-looking  band 
in  the  axis  of  a  glass  rod,- in  the  latter  it  appears  as  a  bright 
scarlet  patch,  completely  concealing  the  white  surface,  and 
obscuring  the  light  which  would  otherwise  be  reflected  by  it. 
If,  however,  the  blood  has  been  subjected  to  any  of  the  pro- 
cesses above  mentioned,  the  appearance  it  presents  in  the  two 
cases  are  materially  altered.  The  blood  in  the  tube  looks 
bright,  because  it  is  translucent,  whereas  that  on  the  porce- 
lain looks  as  dark  as  if  it  were  venous,  because  the  corpuscles 
from  which  the  light  shone,  reflected  by  countless  convex  sur- 
faces, arc  now  scarcely  more  refractive  than  the  liquid  in 
which  they  are  immersed.  In  other  words,  blood  in  the  natu- 
ral state  lias  the  character  of  an  opaque  pigment,  such  as  ver- 
milion ;  whereas  in  the  altered  state  it  resembles  a  lake — a 
fact  which  Rollett,  who,  as  I  have  stated,  has  studied  these 
changes  with  great  exactitude,  expresses  by  the  terms  deck- 


188  THE    BLOOD. 

farbig  and  lackfarbig,  as  applicable  to  the  former  and  the 
latter  respectively.  Blood  may  lie  rendered  transparent  or 
laky  by  exposing  it  cither  to  extreme  cold  or  to  a  temperature 
a  little  above  G0°  C.  ;  by  subjecting  it  to  the  action  either  of 
induced  currents  or  of  shocks  of  frictional  electricity.  A 
similar  effect,  as  already  stated,  is  produced  by  the  addition  of 
water  and  of  various  other  liquid  reagents,  such  as  ether,  chlo- 
roform, and  solutions  of  the  bile  acids  in  combination  with 
alkaline  bases. 

11.  Action  of  Cold. — A  platinum  capsule  containing  a 
couple  of  cubic  centimetres  of  defibrinated  blood  is  exposed 
to  a  temperature  of — 6°  to — 10°  C.,1  by  placing  it  in  a  vessel 
previously  filled  with  alternate  layers  of  pounded  ice  and  salt, 
and  leaving  it  in  contact  with  the  freezing  mixture  until  it  is 
completely  frozen  through.  The  solid  mass  of  blood  is  then 
slowly  thawed  and  poured  into  a  beaker,  which  should  be  of 
such  size  that  the  blood  contained  in  it  is  not  more  than  half 
an  inch  deep.  If  readily  crystallizable  blood  has  been  cm- 
ployed,  as,  for  example,  that  of  the  guineapig,  a  sediment  of 
crystals  forms  on  the  bottom.  It  is  seen  from  the  first  that 
the  freezing  has  completely  altered  its  appearance.  It  has 
become  darker  in  color,  and  if  we  place  some  of  it  on  the  sur- 
face of  a  white  plate  with  a  pattern  on  it,  the  pattern  is  visible 
with  more  or  less  distinctness  through  it,  whereas  if  ordinary 
blood  were  employed  it  would  be  completely  concealed.  It 
is  scarcely  necessary  to  add  that  the  crystallization  is  depend- 
ent on  the  discharge  of  the  haemoglobin  from  the  corpuscles 
into  the  liquor  sanguinis. 

12.  Action  of  Heat.— (Method  of  Max  Schultze.)  This 
is  a  method  which  is  only  applicable  to  small  quantities  of 
blood.  In  experiments  with  the  warm  stage  (see  Chap.  I.,  p. 
22).  Max  Schultze  found  that  when  blood  is  heated  from  60° 
C.  to  G4°  C,  the  blood  corpuscles  dissolve  in  the  plasma. 
The  same  effect  is  produced  if  a  small  quantity  of  blood  is 
subjected  to  similar  temperatures  in  a  hot  chamber,  furnished 
writh  Bunsen's  regulator.  Here,  as  in  the  former  case,  if  the 
blood  is  derived  from  an  animal  in  which  the  haemoglobin 
crystallizes  readily,  crystals  are  obtained.  According  to 
Preyer,  remarkably  fine  crystals  of  haemoglobin  ma3r  be  pre- 
pared by  warming  the  colored  corpuscles  separated  by  subsi- 
dence and  decantation  from  the  defibrinated  blood  of  the 
horse,  in  the  manner  above  described.  To  insure  success, 
care  must  be  taken  to  maintain  the  temperature  of  the  quan- 

1  The  effect  of  subjecting  blood  to  the  temperature  of  a  freezing  mix- 
ture was  first  studied  by  llewsou.  His  experiment  was  similar  to  that 
described  in  the  text.  His  purpose  was  to  show  that  cold  is  not  the 
cause  of  coagulation.  He  was  not  aware  that  frozen  blood  loses  its 
opacity. 


BY   DR.    BURDON-SANDERSON.  189 

tity  of  blood   operated   on  within  the  limits  of  temperature 
above  mentioned. 

13.  Action  of  Electricity. — The  effects  both  of  shocks  of 
friction al  electricit}r  and  of  induced  currents  have  been  de- 
scribed in  the  histological  part.  To  what  is  there  stated,  it 
may  be  added,  as  regards  induced  currents,  that  the  most 
marked  effects  are  produced  when  the  current  is  most  analo- 
gous in  its  characters  to  a  discharge  of  statical  electricity,  and, 
consequently,  that  the  direct  induced  current  which  accompa- 
nies the  opening  of  the  primary  current  is  more  effectual  than 
in  the  inverse  one.  In  the  results  observed,  it  is  important  to 
distinguish  between  the  direct  action  of  the  shock  or  shocks 
on  the  corpuscles,  and  the  electrolytic  action  indicated  b}'  the 
liberation  of  gases  at  the  tinfoil  points  (see  Fig.  194).  In  so 
far  as  electrolysis  occurs,  the  results  may  be  in  part  attributed 
to  the  development  of  acid  reaction  at  the  positive  pole,  con- 
sequent on  the  decomposition  of  the  salts  of  the  blood.  A  dis- 
tinction ought  also  to  be  drawn  between  those  effects  which 
are  only  produced  when  the  corpuscles  are  in  a  living  state, 
and  those  which  are  manifested  also  in  dead  blood.  The 
discharge  of  the  coloring  matter  from  the  corpuscles  is  a  phe- 
nomenon of  the  latter  class,  but  there  are  other  effects  which 
manifest  themselves  only  when  the  blood  emploj'ed  still  retains 
its  vital  properties. 

14.  Action  of  Water  on  the  Blood. — The  mode  of  action 
of  water  on  the  corpuscles  is  full}'  described  in  Chapter  I.  The 
coloring  matter  is  entirely  discharged,  and  probably  the  greater 
part  of  the  globulin.  That  the  whole  is  not  expelled  seems 
evident  from  an  old  experiment,  made  more  than  twent3'-five 
years  ago  b}r  Dr.  Buchanan,  of  Glasgow,  who  observed  that 
the  solid  residue  left  behind,  even  when  repeatedly  washed 
with  distilled  water,  still  retained  the  power  of  determining 
coagulation  in  serous  effusion-liquids,  when  added  to  them  in 
small  quantity.  Again,  when  blood  which  has  been  acted  on 
by  water  is  subjected  to  a  stream  of  carbonic  acid  gas,  the 
stromata  of  the  corpuscles  show  changes  which  indicate  that 
they  still  retain  a  substance  precipitable  by  that  gas. 

15.  Action  of  Crystallized  Ox-bile. — On  the  addition  of 
a  dilute  solution  of ;'  bile  crystals,"  i.  e.,  crystals  of  glyco-cho- 
late  and  tauro-cholate  of  soda  to  blood,  a  great  number  of  the 
corpuscles  are  dissolved,  so  that  the  blood  becomes  distinctly 
laky;  and  if  it  is  derived  from  a  suitable  source,  and  not  too 
much  diluted,  the  coloring  matter  crystallizes.'  On  this  fact 
one  of  the  numerous  methods  of  obtaining  hsemaglobin  is 
founded.  With  reference  to  the  mode  of  obtaining  "  bile 
crystals,"  see  Chap.  XXXVI. 

16.  Preparation  of  Haemoglobin. — Any  method  by  which 
the  coloring  matter  can  be  caused  to  quit  the  corpuscles  without 


100  THE    BLOOD. 

undergoing  chemical  change,  or  in  other  words,  any  of  the 
methods  by  which  the  blood  can  be  rendered  transparent  or 
laky,  may  be  used  for  obtaining  crystalline  haemoglobin.  Many 
of  these  methods  yield  the  product  very  readily,  when  the  blood 
is  derived  from  one  of  those  animals  in  which  the  coloring 
matter  is  prone  to  crystallize.  There  arc,  however,  only  one 
or  two  of  them  by  which  pure  haemoglobin  can  be  obtained  in 
considerable  quantity. 

Thus  by  the  method  of  freezing,  large  well-formed  crystals 
cau  be  obtained  from  the  blood  of  the  guineapig  or  dog.  In 
like  manner  the  blood  of  the  same  animals  crystallizes  readily 
after  it  has  been  rendered  laky  b}r  warming  or  by  the  trans- 
mission of  induction  shocks. 

When  it  is  intended  to  prepare  considerable  quantities  in  a 
state  of  purity,  it  is  best  to  emplo}'  water  as  a  solvent,  and 
then  to  determine  crystallization  in  the  liquid  by  the  addition 
of  alcohol,  in  such  proportions  that  the  mixture  is  only  just 
capable  of  retaining  the  coloring  matter  in  solution.  To  insure 
success,  it  is  to  be  borne  in  mind  that  the  coloring  matter 
crystallizes  as  oxyhemoglobin  (see  §  17), that  crystallization  is 
much  impeded  b}r  the  presence  of  non-crystallizable  organic 
compounds,  particularly  albumin,  and  that  haemoglobin  is 
prone  to  undergo  change  when  exposed  in  solution  to  tempe- 
ratures above  that  of  freezing.  To  insure  complete  oxidation, 
the  blood  must  be  freely  exposed  to  air.  To  obviate  the 
interfering  influence  of  albumin,  the  coloring  matter  must  be 
derived,  not  from  the  whole  of  the  blood,  but  in  as  far  as  pos- 
sible from  the  corpuscles  alone.  To  obviate  the  risk  of  che- 
mical change,  i.  e.,  of  the  splitting  of  the  haemoglobin  into 
other  products,  the  liquids  must  be  subjected,  as  far  as  pos- 
sible, during  the  whole  operation  to  a  low  temperature.  These 
indications  are  fulfilled  in  the  following  process,  devised  by 
Preyer,  which  gives  good  results,  when  the  weather  is  cold 
and  when  blood  is  used  of  which  the  coloring  matter  is  com- 
paratively insoluble  in  water  at  0°  C,  e.  g.,  that  of  the  dog  or 
cat.  The  haemoglobin  of  the  blood  of  the  horse,  on  the  other 
hand,  is  very  soluble  at  all  temperatures.  It  cannot  therefore 
be  prepared  by  Preyer's  method.  Blood  to  be  employed  is 
allowed  to  flow  from  a  vein  or  artery  into  a  porcelain  capsule. 
It  is  then  placed  in  a  cool  cellar  to  coagulate.  On  the  follow- 
ing day  most  of  the  serum  is  poured  off,  and  the  remainder 
removed  with  the  aid  of  a  pipette.  The  clot  is  then  cut  into 
small  fragments  and  placed  on  a  filter  of  fine  calico,  on  which 
it  is  washed  repeatedly  with  ice-cold  distilled  water,  until  the 
washings  give  scarcely  any  precipitate  .with  a  solution  of  cor- 
rosive sublimate.  [This  indicates  that  the  clot  is  tolerably 
free  from  serum-albumin.  The  water  must  be  ice-cold,  because 
at   freezing   temperature   haemoglobin    is   sparingly   soluble.] 


BY  DR.  BURDON-S  ANDERSON.  191 

Then  on  the  filter  the  clot  is  treated  with  distilled  water  at  a 
temperature  of  about  35CC,  the  filtrate  being  allowed  to  drop 
into  a  measure-glass  cooled  in  ice.  It  is  of  great  importance 
that  this  part  of  the  process  should  be  carried  out  with  as  little 
loss  of  time  as  possible.  I  have  found  it  a  good  plan  to  in- 
close the  clot  in  the  filterer,  and  then  to  knead  it  repeatedly  in 
small  quantities  of  warm  water  contained  in  the  capsule;  the 
products  of  all  the  extractions  being  collected  on  the  same 
filter,  and  received  in  the  cooled  beaker.  A  measured  portion 
(say  ten  cubic  centimetres)  is  then  transferred,  with  the  aid  of 
a  pipette,  to  a  test-glass,  to  which  alcohol  is  added  drop  b}' 
drop  from  a  burette.  The  precipitate  formed  by  the  first  drops 
of  alcohol  redissolves  on  shaking  or  stirring:  as  more  alcohol 
is  added  the  precipitate  at  last  remains  undissolved.  [By  this 
means  the  proportion  of  alcohol  required,  in  order  to  diminish 
the  solvent  power  of  the  liquid  sufficiently  to  render  it  prone 
to  crystallize,  is  determined.]  Alcohol  is  then  added  to  the 
whole  liquid,  in  proportion  somewhat  less  than  is  required  to 
produce  a  permanent  precipitate.  The  clear  solution  on  being 
left  to  itself,  surrounded  with  iced  water,  soon  begins  to 
crystallize.  The  crystals  are  separated  by  filtration  and  washed 
on  the  filter  with  ice-cold  water  containing  a  little  spirit,  and 
subsequent^  with  ice-cold  water  alone.  To  obtain  the  sub- 
stance in  a  state  of  purity  it  must  be  subjected  to  recrystalli- 
zation.  For  this  purpose  the  crystals  must  be  dissolved  in 
distilled  water  at  40  °C.  and  evaporated  in  vacuo,  the  process 
being  repeated  until  a  product  is  obtained  which  on  incinera- 
tion leaves  pure  oxide  of  iron  without  trace  of  phosphoric 
acid. 

Dr.  Gamgee  recommends  the  following  process,  which  was 
recently  communicated  to  him  by  Professor  Kuhne,  and  has 
been  successfulby  emploj^ed  by  him  on  three  separate  occasions. 
Five  hundred  cubic  centimetres  of  defibrinated  blood  of  a  dog 
are  mixed  in  a  flask  with  31  c.  c.  of  pure  ether,  and  thoroughly 
shaken  at  intervals  of  a  few  minutes  during  an  hour  and  a  half 
or  two  hours.  The  mixture  is  then  placed  in  a  cellar  for  about 
twentj'-four  or  thirty-six  hours.  The  flask  containing  the  lake- 
red  liquid  is  now  surrounded  with  ice  (not  a  freezing  mixture) 
for  twelve  hours,  at  the  end  of  which  time  it  is  found  to  have 
become  converted  into  a  magma  of  haemoglobin  crystals.  Dr. 
Gamgee  states  that  the  only  objection  to  this  method  consists 
in  the  great  difficulty  of  filtering  the  crystalline  from  the  viscid 
serous  portion  of  the  mixture.  In  laboratories  where  the  cen- 
trifugal apparatus  is  to  be  found,  the  magma  may  be  placed  in 
tubes  and  submitted  to. excessively  rapid  rotation  for  three  or 
four  hours,  at  the  end  of  which  time  the  haemoglobin  will  have 
separated  as  a  soft  cake  from  the  serum,  which  can  be  decanted. 
Where  no  centrifugal  apparatus  can  be  obtained,  the  magma  of 


192  THE    BLOOD. 

crystals  ma}'  be  diluted  by  the  addition  of  an  equal  volume  of 
a  mixture  consisting  of  one  part  of  ninety  per  cent,  alcohol  and 
four  parts  of  distilled  water.  The  whole  must  be  filtered 
through  calico,  and  the  soft  haemoglobin  freed  from  the  greater 
part  of  the  adhering  water  and  spirit  by  being  placed  on  a 
porous  brick  and  exposed  to  a  current  of  cold  air.  Whichever 
method  of  separating  the  crystals  is  used,  they  must  be  purified 
by  recrystallization. 

The  best  method  of  obtaining  haemoglobin  crystals  in  small 
quantities,  for  microscopical  purposes,  is  one  founded  on  the 
same  principles.  A  teaspoonful  of  defibrinated  blood  is  treated 
with  a  sufficient  quantity  of  water  to  render  it  transparent. 
A  quarter  of  its  bulk  of  alcohol  having  been  added  to  it,  the 
mixture  is  introduced  into  a  platinum  capsule,  and  plunged  in 
a  mixture  of  pounded  ice  and  salt.  A  relatively  abundant 
crop  of  crystals  is  obtained.  The  mere  freezing  and  thawing 
the  blood,  as  directed  in  §  11,  will  also  give  satisfactory  re- 
sults. Another  method  consists  in  passing  the  vapor  of  chloro- 
form through  the  blood,  which  has  alwaj^s  the  effect  of  render- 
ing it  laky,  and  in  some  animals  determines  crystallization. 

17.  Chemical  Properties  of  Haemoglobin. — Solubility. 
— The  solubility  of  haemoglobin  in  water  differs  according  to 
the  species  of  animal  from  which  it  is  derived.  Thus  the  color- 
ing matter  of  the  dog  and  cat  are  very  soluble  at  40°  C; 
sparingly  soluble  in  ice-cold  water.  That  of  the  guineapig 
dissolves  with  relative  difficulty  at  all  temperatures,  and  crys- 
tallizes more  readily  than  that  of  any  of  the  common  domestic 
animals.  All  kinds  of  haemoglobin  are  more  soluble  in  warm 
water  than  in  cold.  Diffusibility. — Haemoglobin,  although 
crystallizable,  is  indiffusible.  This  can  be  easily  shown  by 
placing  a  solution  of  blood  or  haemoglobin  in  a  diffusion-cell, 
the  septum  of  which  is  of  good  parchment  paper.1  If  an  animal 
membrane  is  substituted,  a  certain  amount  of  coloring  matter 
passes  from  the  solution  into  the  water.  The  fact  of  the 
diffusibility  of  haemoglobin  perhaps  stands  in  relation  with 
the  enormous  weight  of  its  molecule.  Coagulability. — Aque- 
ous solutions  of  haemoglobin  coagulate  when  heated,  just  in 
the  same  way  as  albumin,  and  at  about  the  same  temperature 
(64°  C).  When  this  occurs,  the  haemoglobin  splits  into  an 
albuminous  compound  and  an  insoluble  coloring  matter.  Pre- 
cipitation by  Alcohol. — Small  quantities  of  alcohol  ma}'  be 
added  to  solutions  of  blood  or  haemoglobin  without  producing 
an}'  appreciable  change.  In  continuing  the  addition  a  precipi- 
tate is  formed,  which  at  first  is  redissolved  on  shaking,  after- 
wards becomes  permanent.    Relation  to  Oxygen. — In  a  solution 

1  For  method  of  preparing  and  testing  a  diffusion-cell,  see  Chapter 
on  Chemical  Methods. 


BY    DR.    BURDON-SANDERSON.  193 

freel}'  exposed  to  air,  the  haemoglobin  is  always  combined  with 
oxygen  (oxyhemoglobin).  Consequently,  whenever  haemo- 
globin is  spoken  of,  it  is  understood  to  mean  oxyhaemoglobin. 
This  oxygen  is  so  loosely  combined,  that  it  begins  to  separate 
itself  from  the  haemoglobin  as  soon  as  the  pressure  of  that 
gas  in  the  gaseous  atmosphere  to  which  it  is  exposed  falls 
below  a  certain  point,  recently  determined  by  Worm  Mullet*  to 
be  about  twenty-five  millimetres  of  mercury.  So  that  when 
blood  is  subjected  to  the  air-pump,  the  haemoglobin  it  contains 
begins  to  part  with  its  oxygen  as  soon  as  the  pressure  is  reduced 
to  about  a  sixth  of  an  atmosphere.  This  is  expressed  by  say- 
ing that  the  tension  of  oxj'gen  in  the  blood  is  about  twenty- 
five  millimetres  Hg.  Haemoglobin  in  solution  can  be  deprived 
of  its  oxygen  by  the  addition  to  the  liquid  of  certain  reducing 
agents  (see  §  18).  In  animals  completely  deprived  of  air,  the 
haemoglobin  in  the  blood  loses  its  oxygen  completely  in  less 
than  a  minute  (see  §  111).  This  is,  no  doubt,  owing  to  the 
rapid  accumulation  in  the  blood  of  oxidizable  products.  When 
blood  or  solution  of  haemoglobin  is  subjected  to  the  barometer 
vacuum  (see  Gases  of  the  Blood),  it  parts  with  the  whole  of 
its  oxygen.  Haemoglobin  has  the  property  of  oxydizing  tinc- 
ture of  guaiacum.  If  a  drop  of  concentrated  solution  of  guaiac 
resin  in  absolute  alcohol  is  dropped  on  to  filtering  paper,  and 
the  alcohol  allowed  to  evaporate,  and  then  a  drop  of  solution 
placed  on  the  brown  spot,  a  deep  blue  ring  is  formed  round 
the  edge  of  the  drop.  This  reaction  must  not  be  confused 
with  that  observed  when  fibrin  steeped  in  peroxide  of  hydro- 
gen produces  a  similar  effect.  In  the  latter  case,  all  that  is 
shown  is,  that  fibrin  decomposes  the  peroxide;  in  the  former, 
the  reaction  a  fiords  evidence  of  the  presence  of  nascent  oxy- 
gen. Action  of  Carbonic  Acid — Blood  which  has  been  satu- 
rated with  carbonic  oxide  is  entirely  deprived  of  its  oxj-gen, 
which  is  replaced  by  an  equal  volume  of  carbonic  oxide.  On 
this  fact  is  founded  the  excellent  method  of  Bernard  for  the 
gasometrical  determination  of  the  oxygen  of  the  blood  (see 
§  32).  The  carbonic  oxide  combines  with  haemoglobin  in  the 
same  way  that  oxygen  does.  Action  of  Oxide  of  Nitrogen. — 
When  oxide  of  Nitrogen  is  passed  through  a  solution  of  blood 
which  has  been  freed  from  oxygen,  by  subjecting  it  to  an  atmos- 
phere of  hydrogen  in  such  a  manner  as  to  exclude  atmospheric 
air  during  the  process,  the  dark  blood  acquires  a  carmine  color. 
Here,  as  in  the  case  of  carbonic  oxide,  a  new  compound  is 
formed  with  haemoglobin,  which  crystallizes  in  the  same  form 
as  oxyhemoglobin.  The  solution,  however,  undergoes  no 
change  when  treated  with  reducing  agents.  Action  of  Nitrites. 
— Dr.  Gamgee  has  shown  that  the  blood  of  animals  poisoned 
with  nitrites,  as  e.g.,  nitrite  of  amy],  assumes  a  chocolate 
color.  This  color  may  be  observed  strikingly  if  a  few  drops 
13 


194  THE    BLOOD. 

of  nitrite  of  amy!  are  added  to  a  solution  of  haemoglobin.  The 
color  of  the  latter  almost  instantly  becomes  brown.  On  adding 
reducing  agents  to  solutions  so  altered,  reduced  haemoglobin 
(see  §  18)  appears — a  fact  which  seems  to  square  hest  with  the 
assumption  that  the  action  of  the  nitrites  on  haemoglobin  is  to 
peroxidize  it,  and  that  on  reduction,  oxyhemoglobin  is  first 
formed,  then  reduced.  The  precise  nature  of  the  reaction  is 
still  matter  for  investigation. 

18.  Optical  Properties  of  Haemoglobin. —  Crystals. — 
The  crystals  are  doubly  refractive,  ?'.  e.,  they  look  luminous 
when  examined  with  the  aid  of  the  polarization  microscope  (see 
Part  I.,  Chap.  IV.),  between  'crossed  Nicols.  They  shine  in 
sunlight  with  a  lustre  compared  by  Preyer  to  that  of  silk. 
When  formed  in  liquids  freely  exposed  to  air  or  ox}rgen,  they 
are  of  the  color  of  arterial  blood,  but  have  the  wonderful  pro- 
perty of  becoming  dark  without  altering  their  form  when  placed 
in  vacuo  at  a  low  temperature.  They  then  exhibit  two  colors, 
looking  green  along  the  arUts^  purplish-red  elsewhere.  On  the 
admission  of  air  or  oxygen,  the  color  is  restored.  If  a  glass 
plate  to  which  crystals  of  hiemoglobin  adhere  is  placed  in  front 
of  the  slit  of  the  spectroscope,  two  characteristic  absorption 
bands  (Hoppe-Seyler)  are  seen  in  the  3'ellow  between  the  Frau- 
enhofer's  lines  D  and  E  (see  Fig.  195,  1).  Solution. — The  bands 
just  mentioned  are  also  seen  when  solution  of  haemoglobin  or 
of  blood  corpuscles  is  placed  in  the  same  position  :  they  can 
be  distinguished  even  when  the  solution  contains  only  one  ten- 
thousandth  of  its  weight  of  coloring  matter.  The  bands  differ, 
however,  in  their  characters  according  to  the  degree  of  dilu- 
tion. According  to  the  experiments  of  Prej'er,  solutions  vary- 
ing in  strength  from  one  to  five  per  10,000,  show  both  bands 
faintly  ;  in  solutions  of  six  per  10,000,  it  can  be  distinguished 
that  the  band  next  the  line  P  is  the  darker  of  the  two,  the  other 
being  broader  and  fainter  (see  Fig.  195,5);  in  solutions  of 
thirty  per  10,000,  the  violet  end  of  the  spectrum  is  completely 
absorbed,  and  the  blue  partially.  As  the  concentration  is  in- 
creased the  two  bands  approach  each  other,  until  finally  (when 
the  solution  contains  seventy  per  10,000)  they  form  a  single 
band,  while  the  whole  of  the  more  refrangible  rays  are  absorbed, 
so  that  the  spectrum  does  not  extend  beyond  the  limits  of  the 
green  (see  Fig.  195,  ft). 

In  18G2  it  was  discovered  by  Stokes  that  haemoglobin  exists 
•in  the  blood  in  two  states  of  oxidation,  which  are  distinguished 
alike  bjr  color  and  by  the  spectroscope;  that  the  oxygenized 
haemoglobin,  or  (as  it  has  since  been  called)  oxyhemoglobin,  is 
deprived  by  reducing  agents  of  its  oxygen,  and  that  when  it 
has  been  so  reduced,  it  can  be  restored  to  its  original  state  by 
agitation  with  air.  The  nature  of  the  change  of  color  is  ex- 
pressed in  two  facts,  which  can  be  observed  with  the  aid  of  the 


BY    DR.    BURDON-SANDERSON.  If' 5 

spectroscope.  The  first  is,  that  when  solutions  of  haemoglobin, 
or  of  blood,  are  deprived  of  oxygen,  either  by  placing  them  in 
vacuo  or  by  the  addition  of  reducing  agents,  the  more  refran- 
gible rays  (blue  and  violet)  are  much  less  absorbed,  and  the 
green  more  absorbed  than  they  were  before.  The  second  fact 
is,  that  in  solutions  so  concentrated  that  most  of  the  spectrum 
is  extinguished,  the  last  color  winch  is  transmitted  is  orange- 
red  if  the  blood  is  arterial,  red  if  it  is  venous.  These  two  facts 
may  be  shortly  expressed  by  saying  that  the  color  of  arterial- 
ized  blood  consists  of  orange-red  plus  green,  of  venous  blood- 
red  plus  blue. 

These  differences,  however,  are  not  the  most  remarkable 
which  are  observed  when  oxydized  and  reduced  solutions  of 
blood  or  its  coloring  matter  are  compared  spectroscopically. 
The  most  striking  change  produced  by  reduction  relates  to  the 
two  bands  of  absorption  in  the  yellow  part  of  the  spectrum 
whieh  have  been  already  mentioned.  This  change  is  most 
readily  demonstrated  by  following  the  directions  given  by 
Stokes  in  his  original  paper.  A  solution  of  protosulphate  of 
iron,  to  which  a  sufficient  quantity  of  tartaric  acid  has  been 
added  to  prevent  its  being  precipitated  by  alkalies,  is  rendered 
decidedly  alkaline  by  the  addition  of  ammonia,  and  is  intro- 
duced into  the  solution  of  blood.  "The  color  is  almost  in- 
stantly changed  to  a  much  more  purple  red,  as  seen  in  small 
thicknesses,  and  a  much  darker  red  than  before,  as  seen  in 
greater  thickness.  The  change  of  color,  which  recalls  the  dif- 
ference between  arterial  and  venous  blood,  is  striking  enough, 
but  the  change  in  the  absorption  spectrum  is  far  more  decisive. 
The  two  highly  characteristic  dark  bands  seen  before,  are  now 
replaced  by  a  single  band,  somewhat  broader  and  less  sharply 
defined  at  its  edges  than  either  of  the  former,  and  occupying 
nearly  the  position  of  the  bright  band  separating  the  dark  bands 
of  the  original  solution  (see  Fig.  195,  2).  The  fluid  is  more 
transparent  for  the  blue,  and  less  so  for  the  green  than  it  was 
before.  If  the  thickness  be  increased  till  the  whole  of  the  spec- 
trum more  refrangible  than  the  red  be  on  the  point  of  disap- 
pearing, the  last  part  to  remain  is  green,  a  little  beyond  the 
fixed  line  6,  in  the  case  of  the  original  solution  ;  and  blue,  some 
way  beyond  F,in  the  case  of  the  modified  fluid.  If  the  purple 
solution  be  exposed  to  the  air  in  a  shallow  vessel,  it  quickl}' 
returns  to  its  original  condition,  showing  the  same  two  char- 
acteristic bands  as  before;  and  this  change  takes  place  imme- 
diately, provided  a  small  quantity  only  of  the  reducing  agent 
were  employed,  when  the  solution  is  shaken  up  with  air.  if 
an  additional  quantity  of  the  reagent  be  now  added,  the  same 
effect  is  produced  as  at  first,  and  the  solution  may  thus  be 
made  to  •uy  through  its  changes  any  number  of  times."  [Stokes, 
On  the  Reduction  and  Oxydation  of  the  Coloring  Matter  of 


196  THE    BLOOD. 

the  Blood.  Proceedings  of  the  Roy.  Soc.,  vol.  xiii.  p.  355.] 
The  same  facts  can  be  demonstrated  quite  as  advantageously, 
and  perhaps  with  greater  ease,  if  the  solution  of  the  sulphhy- 
drate  of  ammonium  is  substituted  for  the  solution  of  sulphate 
of  iron  used  by  Stokes.  The  change  is,  however,  not  so  rapid: 
it  is  accelerated  by  subjecting  the  liquid  to  a  temperature  of 
40°  C. 

19.  Methaemoglobin. — If  a  pure  solution  of  haemaglobin 
is  left  to  itself  at  the  ordinary  temperature,  it  gradually  loses 
its  brightness,  and  if  it  is  then  examined  spcctroscopically,  it 
is  seen  that  a  new  band  has  appeared  in  the  orange  at  a  point 
where  in  ordinary  blood  there  is  least  absorption.  This  band 
is  due  to  the  presence  of  a  new  coloring  matter,  called  by 
Hoppe-Seyler  methaemoglobin.  The  same  change  occurs  under 
other  circumstances,  e.g.,  when  carbonic  acid  gas  is  passed 
through  dilute  solutions  of  haemaglobin,  or  when  glacial  acetic 
acid  is  added  to  dilute  solution  of  defibrinated  ox-blood,  in  ex- 
tremely small  quantity.  [In  larger  proportions,  acetic  acid 
determines  the  formation  of  haematon. — See  §  22.]  Haemoglo- 
bin undergoes  the  same  transformation  when  acted  on  by  per- 
manganate of  potash.  If  a  crystal  of  pure  permanganate  is 
dissolved  in  distilled  water,  and  the  solution  added  to  very 
dilute  solution  of  blood,  before  the  slit  of  the  spectroscope,  at 
a  temperature  of  about  25°  C,  the  haemoglobin  bands  gradu- 
ally disappear.  In  their  place  we  have  a  spectrum,  in  which 
there  are  not  only  the  band  mentioned  above,  but  two  others, 
of  which  one  nearly  corresponds  in  position  to  the  second  hae- 
moglobin  band,  while  the  other  lies  half  way  between  the  lines 
E  and  F.  Methaemoglobin  is  a  substance  of  which  the  chemi- 
cal constitution  and  relations  are  imperfectly  ascertained.  Its 
presence  is  indicated  spectroscopically  in  all  collections  of 
blood  which  have  been  for  some  time  extravasated  within  the 
body,  e.  g.,  in  thrombi,  sanguinolent  transudation  liquids,  etc. 

20.  Preparation  of  the  Crystalline  Coloring  Matters 
■which  result  from  the  Decomposition  of  Haemoglo- 
bin, and  Demonstration  of  their  Absorption  Spectra. — 
Hasmin. — When  dried  blood  is  treated  with  glacial  acetic  acid 
and  warmed  to  the  temperature  of  the  body,  a  solution  is  ob- 
tained which  yields  crystals  of  a  new  coloring  matter,  of  re- 
markable properties,  which  has  been  designated  haemin.  The 
erystals  vary  extremely  in  shape,  sometimes  occurring  as 
rhombic  plates,  sometimes  as  rods  crossing  each  other  at  vari- 
ous angles.  They  are  not  soluble  without  decomposition  in 
any  liquid  excepting  hydrochloric  acid,  and  are  so  little  liable 
to  chemical  change  that  they  may  be  kept  for  years,  exposed 
to  a  moist  atmosphere,  without  undergoing  any  change.  Hae- 
min difl'ers  from  haematin  (§  21)  in  containing  an  additional 
equivalent  of  hydrochloric  acid,  on  which  account  it  is  also 


BY   DR.    BURDON-SANDERSON.  197 

called  hydro-chlorate  of  haematin.  Its  carbon,  nitrogen,  and 
iron  are  in  the  same  relative  proportions  as  in  haematin,  but 
necessarily  it  contains  a  little  less  iron  per  cent,  than  that 
body. 

The  mode  of  preparing  the  so-called  Teichmann's  crystals — 
in  other  words,  the  mode  of  obtaining  haemin  for  the  purpose 
of  demonstrating  its  crystalline  form  microscopically — has 
been  fully  described  in  the  histological  part  (Chap.  I.,  p.  34). 
Haemin  majr  be  obtained  from  blood  in  quantity,  as  follows, 
but  the  process  is  one  which  appears  to  present  great  difficulty, 
as  it  frequently  fails.  Defibrinated  blood  is  diluted  with  a  vol- 
ume and  a  half  of  distilled  water.  The  transparent  liquid  is 
then  precipitated  with  neutral  acetate  of  lead,  for  the  purpose 
of  separating  the  albumin.  The  excess  of  lead  (with  respect 
to  which  it  is  desirable  to  be  careful  not  to  add  more  than  is 
necessary)  having  been  got  rid  of  by  the  addition  of  a  con- 
centrated solution  of  carbonate  of  soda,  the  liquid  is  filtered, 
and  the  filtrate  evaporated  to  dryness  either  in  the  air  or  in 
vacuo.  The  dry  residue  is  then  finely  powdered  and  rubbed 
up  with  fifteen  times  its  own  weight  of  glacial  acetic  acid,  to 
which  a  trace  of  chloride  of  sodium  has  been  added.  The 
brown  liquid  thus  obtained  is  introduced  into  a  flask  and 
warmed  in  the  water  bath  until  it  is  entirely  dissolved,  and  the 
solution  is  mixed  with  five  times  as  much  distilled  water,  and 
allowed  to  stand  for  many  days,  protected  from  evaporation. 
The  crystals  collect  on  the  bottom  of  the  beaker  and  may  be 
readily  purified  by  repeatedly  treating  them  with  distilled 
water,  allowing  them  to  subside  and  then  decanting.  As  hae- 
min  contains  chlorin,  it  cannot  be  prepared  from  haematin 
unless  chlorides  be  present.  When  it  is  prepared  from  blood, 
the  quantity  of  chloride  of  sodium  present  is  sufficient,  so  that 
the  addition  of  that  salt  is  not  essential.  The  solution  of  hae- 
min in  hydrochloric  acid  gives  no  characteristic  spectrum. 

21.  Haematin. — Haematin  can  only  be  obtained  in  a  state 
of  perfect  purity  from  the  crystals  of  haemin,  the  mode  of  pre- 
paration of  which  has  just  been  given.  The  process  is  simple  : 
the  haemin  crystals  are  dissolved,  i.  e.,  decomposed  in  ammonia. 
The  solution  of  haematin  thus  obtained  is  evaporated  to  dry- 
ness, the  residue  is  then  extracted  with  water,  which  removes 
the  chloride  of  ammonium,  and  dried.  The  product  is  pure 
haematin.  It  is  insoluble  in  water,  alcohol,  and  ether,  soluble 
in  alkalies  and  alkaline  carbonates,  but  not  soluble  in  acids 
without  decomposition. 

In  the  impure  state,  haematin  may  be  obtained  in  various 
ways.  The  change  occurs  more  gradually  at  ordinary  tem- 
peratures in  solutions  of  blood,  or  haemoglobin,  which  are  de- 
cidedly alkaline,  whether  the  alkalinity  is  derived  from  potash, 
soda,  ammonia,  or  their  carbonates.     Solutions  of  haemoglobin 


108  TIIE    BLOOD. 

which  have  undergone  this  last  change  exhibit,  when  placed 
before  the  slit  of  the  spectroscope,  in  place  of  the  haemoglobin 
bands,  a  less  distinct  and  paler  bund  on  the  opposite  side  of 
the  D  line,  i.  t\,  in  the  orange.  This  change  is  characteristic 
of  the  presence  of  hsematin.  It  is  attended  with  an  obvious 
darkening  of  the  color  of  the  liquid. 

When  an  alkaline  solution  of  haematin  is  subjected  to  the 
action  of  reducing  agents,  such  as  sulphuret  of  ammonium  or 
protosulphate  of  iron,  it  exhibits,  when  examined  spectroscopi- 
cally,  two  much  more  distinct  bands  (Fig.  195,  4),  one  of  which 
is  exactly  opposite  the  bright  space  which  separates  the  two 
haemoglobin  bands  ;  the  other,  which  is  less  intense,  is  close  to 
Frauenhofer's  line,  E,  i.  e.,  nearer  to  the  blue  end  of  the  spec- 
trum than  the  broader  of  the  two  haemoglobin  bands.  If  the 
solution  is  fresh  and  dilute,  and  the  quantity  of  the  reducing 
agent  small,  these  bands  can  be  made  to  vanish  b}'  agitation 
with  air,  giving  way  to  the  so-called  oxyhaematin  band  above 
described.  All  these  facts  ma}7  be  as  readily  demonstrated  in 
solutions  of  blood  corpuscles  ;  i.  p.,  of  cruor,  as  in  solutions  of 
haemoglobin.  Blood  rendered  distinctl}r  alkaline  either  by  soda, 
potash,  ammonia,  or  their  carbonates,  shows  the  absorption 
band  of  oxyhaematin.  After  addition  of  sulphuret  of  ammo- 
nium, this  is  replaced  by  the  more  distinct  spectrum  of  reduced 
hsematin. 

22.  Haematoin. — When  acetic  acid  is  added  to  blood,  the 
iron  of  the  haemoglobin  is  separated  and  takes  the  form  of  a 
protosalt,  and  a  new  coloring  matter  remains  in  solution,  the 
spectrum  of  which  was  first  described  by  Professor  Stokes,  and 
has  been  subsequently  known  as  acid  hsematin.  More  recently, 
Preyer  has  shown  that  it  is  not  identical  with  hsematin,  but 
with  the  body  to  which  Hoppe-Seyler  gave  the  name  of  iron-free 
hsematin.  It  is  produced  whenever  concenti'ated  sulphuric 
acid  acts  on  haematin.  According  to  Hoppe-Se3Tler,  it  is  pre- 
pared by  rubbing  up  finely  powdered  hsematin  in  concentrated 
sulphuric  acid.  A  liquid  is  obtained  which  is  green  in  thin 
layers,  reddish-brown  in  thicker  layers,  and  gives  a  brown  pre- 
cipitate when  diluted  with  water.  This  precipitate  is  easily 
dissolved  in  ammonia.  On  evaporating  the  ammoniacal  solu- 
tion, a  bluish-black  residue  with  metallic  lustre  is  left,  wdiich  is 
free  from  iron.  It  may  be  obtained  in  like  manner  by  acting 
on  methaemoglobin  by  sulphuric  acid.  The  solution  of  haema- 
toin in  ammonia  exhibits  four  absorption  bands.  It  is  ad- 
mirably shown  b}r  the  method  recommended  by  Professor 
Stokes,  i.  e.<  by  extracting  with  ether  blood  which  has  been 
mixed  with  acetic  acid.  The  ethereal  liquid  thus  obtained  ex- 
hibits a  four-banded  spectrum.  Of  these  bands,  three  onl}' are 
easy  to  recognize — one  in  the  orange,  nearer  to  the  red  than 
the  reduced  hsematin  band  ;  a  rather  broad  band  in  the  green; 


BY    DR.    BURDON-S ANDERSON.  199 

and    a   narrow  but  well-defined   one   in  the  blue.      (See  fig. 
195,  3.) 

23.  Quantitative  Analysis  of  the  Blood,  with  refer- 
ence to  its  Corpuscles,  Serum,  Fibrin,  Haemoglobin, 
Albumin,  and  Salts. — The  following  summary  of  the  order 
of  proceeding  in  the  analysis  of  the  blood,  will  be  found 
sufficient  for  the  guidance  of  those  who  have  been  previously 
trained  in  quantitative  methods.  The  student  who  has  not 
learnt  accuracy  by  practice,  in  the  analysis  of  bodies  of  known 
composition  in  the  chemical  laboratory,  should  not  attempt 
the  quantitative  determinations  relating  to  the  blood  or  other 
animal  liquids,  partly  because  the  operations  are  complicated, 
but  principally  because  the  operator  has  no  means  of  detecting 
his  mistakes.  The  blood  to  be  analyzed  is  received  in  four 
vessels,  the  contents  of  which  are  as  follow:  1.  Ten  or 
twelve  centimetres  of  blood  are  allowed  to  flow  into  a  weighed 
porcelain  capsule  and  covered  with  a  weighed  watch-glass: 
After  weighing,  the  blood  is  evaporated  in  a  water-bath,  dried 
in  the  air-bath  at  120°  C,  and  the  residue  used  for  the  deter- 
mination of  the  total  albuminous  constituents,  fat  and  salts,  as 
follows:  After  standing  till  it  is  cool  in  a  receiver  over  sul- 
phuric acid,  it  is  weighed.  The  weight,  deducted  from  that  of 
the  capsule  and  watch-glass,  gives  the  total  solids.  The  dry 
residue  is  then  pulverized  in  a  glass  or  porcelain  mortar  with 
common  alcohol  (Sp.  G.  890)  and  transferred  to  a  small  beaker, 
the  mortar  being  subsequently  carefully  washed  with  alcohol, 
and  the  washings  added  to  the  quantity  in  the  beaker.  This 
done,  the  contents  of  the  beaker  are  boiled,  and  the  alcoholic 
solution  thus  obtained  is  poured  into  a  small  previously 
weighed  filter.  What  remains  in  the  beaker  is  similarly 
treated  with  a  second  quantity  of  alcohol,  which  is  thereupon 
poured  into  the  same  filter.  After  carefully  washing  the  filter 
with  boiling  alcohol,  the  filtrate  together  with  the  washings 
is  evaporated  on  the  water-bath,  dried  at  110°  C,  allowed  to 
cool  over  sulphuric  acid,  and  weighed.  The  weight  gives  the 
solids  soluble  in  alcohol a. 

Distilled  water  is  added  to  the  residue  in  the  beaker,  which 
is  warmed  in  the  water-bath.  The  water-extract  is  then  poured 
on  to  the  filter  last  used,  and  the  filtrate  collected  in  a  weighed 
covered  capsule,  evaporated  on  the  water-bath,  dried  at  110°, 
cooled  over  sulphuric  acid,  and  weighed.  The  weight,  minus 
that  of  the  capsule,  is  that  of  the  solids  soluble  in  water    .     b. 

The  remainder  on  the  filter  is  dried  at  110°,  and  then  over 
sulphuric  acid,  and  weighed  repeatedly,  till  it  is  found  no 
longer  to  lose  weight.  For  this  purpose  it  must  be  inclosed 
between  two  watch-glasses,  held  together  by  a  clamp.  The 
weight,  minus  that  of  the  watch-glasses,  filter,  etc.,  is  that  of 
the  insoluble  solids c. 


200  THE    BLOOD. 

The  fats  of  the  blood  are  contained  in  a,  from  which  they 
are  extracted  by  repeatedly  treating  it  with  ether  and  evapo- 
rating the  ethereal  extract.  The  residue  is  washed  into  a 
small  platinum  capsule  for  incineration. 

b  is  incinerated  in  the  capsule  in  which  it  was  weighed  ;  c, 
with  the  filter  in  which  it  is  contained,  is  incinerated  in  another 
capsule.  The  ash  of  a  and  b  represents  the  soluble  salts  of 
the  blood,  viz.,  the  chloride  of  sodium  (five-sixths  of  the 
whole),  phosphate,  sulphate,  and  carbonate  of  soda ;  chloride 
and  sulphate  of  potash.  The  ash  of  c  consists  of  phosphates 
of  lime  and  magnesia.1 

2.  A  second  quantity  of  twenty-five  centimetres  is  used  for 
the  determination  of  the  fibrin.  For  this  purpose  a  small 
beaker  is  used,  over  the  top  of  which  a  vulcanized  India-rubber 
cap  with  a  single  neck  (see  Fig.  190)  can  be  drawn  without 
difficulty.  Through  the  neck  or  tubulature,  a  rod  of  whale- 
bone, which,  at  its  lower  end,  widens  out  into  a  blade,  is 
grasped  by  the  tubulature.  The  blood  is  received  into  the 
beaker,  covered  at  once  with  the  cap,  and  immediately  agitated 
very  briskly  with  the  blade  of  the  whalebone,  the  purpose  of 
the  whole  arrangement  being  to  prevent  loss  of  weight  by 
evaporation  during  the  process.  As  soon  as  coagulation  is 
complete,  the  beaker  and  its  contents  are  weighed.  The 
weight,  minus  that  of  the  beaker,  its  cover  and  the  oar,  is  that 
of  the  quantity  of  blood  used.  The  cover  is  then  removed 
and  the  beaker  filled  with  water,  to  which  a  trace  of  chloride 
of  sodium  has  been  added.  After  agitation  and  subsidence 
the  clear  liquid  is  poured  off,  and  the  fibrin  again  treated  with 
as  much  more  water  with  a  trace  of  salt.  The  fibrin  is  then 
collected  on  a  weighed  filter,  and  washed  with  distilled  water 

1  In  incinerating,  it  is  of  importance  that  the  capsule  or  crucible 
should  be  large  enough  to  hold  four  or  five  times  as  much  material  as  is 
used.  Platinum  vessels  are  preferable.  If  the  substance  contains  much 
organic  matter,  and  at  the  same  time  much  soluble  salts,  e.  g.,  chlorides, 
it  is  necessary  to  perform  the  operation  in  two  stages,  i.  e.,  first  to  car- 
bonize the  substance,  then  extract  the  ash  with  boiling  water,  collect 
the  insoluble  part  on  a  filter  free  from  ash  or  containing  a  known 
weight  of  ash.  The  filter,  after  careful  washing,  must  be  dried  at 
110°  C,  and  gradually  heated  to  whiteness  until  the  carbon  is  entirely 
destroyed.  Almost  the  whole  of  the  soluble  salts  are  contained  in  the 
extracts.  Thus  the  decomposition  of  the  alkaline  carbonates  and 
chlorides,  which  occurs  at  a  higher  temperature,  is  avoided.  In  incine- 
ration of  the  total  solids  of  the  blood  this  interruption  of  the  process  is 
desirable,  if  for  no  other  reason,  on  account  of  the  extreme  difficulty  of 
getting  rid  of  the  carbon  in  presence  of  so  great  a  quantity  of  alkaline 
salts.  If,  however,  the  method  described  in  the  text  is  followed,  these 
difficulties  are  got  rid  of  in  another  way.  For,  on  the  one  hand,  the 
watery  and  alcoholic  Extracts  contain  very  little  organic  matter  ;  on 
the  other,  the  insoluble  residue  (c)  is  free  from  alkaline  salts.  In  both 
cases,  therefore,  the  incineration  can  be  proceeded  with  continuously. 


BY    DR.    BURDON-SANDERSON.  201 

until  the  filtrate  is  colorless.  The  pink  fibrin  thus  obtained  is 
then  finally  washed  on  the  filter  with  boiling  alcohol,  dried 
first  in  the  air-bath,  then  over  sulphuric  acid,  and  finally 
weighed. 

3.  A  third  portion  of  blood  is  received  in  a  similar  apparatus, 
defibrinated,  and  the  defibrinated  blood  strained  through  a 
calico  filter  and  weighed.  The  filtrate  is  then  mixed  in  a  tall 
jar,  with  ten  volumes  of  a  solution  of  salt,  prepared  by  adding 
nine  volumes  of  water  to  one  of  saturated  solution.  After  a 
day,  the  corpuscles  having  subsided,  the  liquid  is  decanted 
off,  and  replaced  by  a  second  similar  quantity  of  saline  solu- 
tion. Again  the  corpuscles  are  allowed  to  subside,  and  the 
liquor  removed  by  decantation.  The  deposit  is  then  washed 
with  water  into  a  porcelain  capsule,  evaporated  on  the  water- 
bath,  dried,  pulverized  with  alcohol,  and  then  proceeded  with 
for  the  separation  of  the  albuminous  compounds  from  the 
soluble  constituents,  as  in  the  first  quantity.  The  weight  of 
the  insoluble  residue  (c),  minus  the  weight  of  its  salts,  corre- 
sponds to  that  of  the  albumin  and  haemoglobin  of  the  whole 
blood. 

4.  The  fourth  quantity  is  allowed  to  coagulate  in  a  capsule. 
The  serum  is  then  poured  off,  and  the  albumin  contained  in 
a  weighed  quantity  determined  by  the  method  already  de- 
scribed. 

The  results  stand  as  follows  :  From  3,  we  learn  the  propor- 
tion in  a  known  weight  of  blood,  of  albumin  and  haemoglobin 
contained  in  the  corpuscles ;  from  1,  the  corresponding  pro- 
portion of  albumin  and  haemoglobin  contained  in  the  corpus- 
cles and  plasma  together;  and  hence,  by  deducting  the  former 
from  the  latter,  the  proportion  of  albumin  in  the  plasma. 
From  4,  the  proportion  of  albumin  contained  in  the  serum  is 
known,  and  thereby  that  of  the  serum  in  the  blood.  The 
weight  of  the  plasma  is  equal  to  the  weight  of  the  fibrin  (2), 
plus  that  of  the  serum.  Finally,  by  deducting  the  weight  of 
the  plasma  from  that  of  the  blood,  we  have  that  of  the  corpus- 
cles in  the  moist. 

24.  Quantitative  Determination  of  the  Haemoglobin 
contained  in  Blood. — It  is  often  of  great  importance  to  be 
able  to  determine  the  proportion  of  haemoglobin  in  a  small 
quantity  of  blood  ;  such,  for  example,  as  may  be  obtained  by 
cupping.  This  is  accomplished  by  making  a  solution  of  a 
measured  or  weighed  quantity  of  blood  in  water,  and  then 
ascertaining,  with  the  aid  of  the  spectroscope,  what  degree  of 
dilution  is  necessary  in  order  to  bring  it  to  such  a  strength 
that  only  the  red  rays  are  transmitted  {see  §  18).  The  point 
of  dilution  at  which  the  green  is  entirely  extinguished,  has 
been  found  by  Preyer  to  be  so  constant,  that  it  may  be  used 
as  a  basis  for  quantitative  determinations. 


202  THE    BLOOD. 

The  determination  of  the  percentage  of  haemoglobin  which 
is  required  to  yield  the  spectroscopic  result  above  described, 
is  accomplished  by  introducing  a  concentrated  solution  of  a 
known  weight  of  pure  haemoglobin  crystals  into  a  glass  cham- 
ber ( so-called  hannatinomcter),  of  which  the  parallel  sides  are 
one  centimetre  from  each  other.  .  The  chamber  is  then  placed 
in  front  of  the  slit  of  the  spectroscope,  the  source  of  light 
being  a  paraffin  lamp.  Distilled  water  is  then  carefully  added 
from  a  finely  divided  burette,  so  \omx  as  all  of  the  spectrum  is 
extinguished  excepting  the  red.  The  moment  that  the  green 
begins  to  appear,  the  operation  is  ended.  The  volume  of  the 
diluted  solution  is  determined  ;  and  the  exact  conditions,  viz., 
the  distance  of  the  lamp  and  chamber,  and  the  width  of  the 
slit,  are  carefully  noted.  The  percentage  of  haemoglobin  con- 
tained in  the  solution  is  that  at  which,  uncle?'  the  given  condi- 
tions, complete  absorption  of  the  green  takes  place.  It  may 
be  designated k. 

In  order  to  ascertain  the  percentage  of  haemoglobin  con- 
tained in  any  given  specimen  of  blood,  all  that  is  required  is 
to  repeat  the  process  just  described.  A  small  quantity  of 
fresh  blood,  which  has  been  well  agitated  with  air  and  defibri- 
nated,  is  introduced  into  a  finely  graduated  small  pipette, 
from  which  exactly  one  centimetre  is  delivered  into  the  glass 
chamber  above  mentioned,  and  diluted  before  the  slit  of  the 
spectroscope  (the  liquid  being  carefully  stirred  after  each 
addition)  until  the  green  begins  to  appear.  At  this  moment 
the  liquid  contains  a  percentage  of  haemoglobin  equal  to  k. 
If  the  volume  of  distilled  water  including  the  centimetre 
originally  added,  be  designated  c,  and  the  original  volume  of 
blood  6,  the  percentage  of  haemoglobin  which  the  blood  con- 
tains is  readily  calculated  according  to  the  formula 

CC  I)  -J—  0    ■ .  T 

— =_J_  Whence,  if  the  quantity  of  blood   used,  as  above 
k         b  H  J  ' 

supposed,  be  one  centimetre,  we  have  x=k  (1  +  c). 

25.  Determination  cf  the  Quantity  of  Haemoglobin 
in  Blood,  by  the  Estimation  of  its  Iron. — Assuming 
that  haemoglobin  contains  0.42  per  cent,  of  iron,  and  that  the 
whole  of  the  iron  of  the  blood  is  contained  in  its  coloring 
matter,  it  is  evident  that  if  the  percentage  of  iron  existing  in 
any  quantity  of  blood  is  known,  the  percentage  of  haemoglobin 
can  be  readily  calculated.  Although  the  process  has  disad- 
vantages as  compared  with  that  last  described,  both  as  regards 
the  time  required  for  carrying  it  out,  and  the  accuracy  of  the 
results,  it  cannot  be  omitted,  as,  under  man}*  circumstances 
(e.g.,  when  the  blood  to  be  investigated  is  not  perfectlj-  fresh), 
the  spectroscopic  method  is  inapplicable.  To  ascertain  the 
proportion  of  iron  in  blood,  a  weighed  or  measured  quantity 
of  the  liquid  must  be  incinerated.     The  ash  must  then  be  dis- 


BY   DR.    BURDON-SANDERSON.  203 

solved  in  pure  dilute  hydrochloric  acid,  and  the  iron  deter- 
mined volumetricalty  with  permanganate  of  potash.  This  is 
accomplished  as  follows  : — 

The  volumetrical  solution  of  permanganate  which  is  usual- 
ly employed,  is  prepared  by  dissolving  the  pure  crystals  in 
distilled  water,  in  the  proportion  of  3.16  grammes  to  the  litre. 
It  is  of  such  strength  that  17.85  centimetres  correspond  ap- 
proximatively  to  one-tenth  of  a  gramme  of  metallic  iron.  It 
is,  however,  necessary,  before  using  it,  to  determine  its  exact 
strength,  by  means  of  a  weighed  quantity  of  solution  of  the 
double  sulphate  of  iron  and  ammonia.  The  mode  of  preparing 
this  salt  will  be  found  in  Sutton's  "  Volumetrical  Analysis." 
It  contains  exactly  one-seventh  of  its  weight  of  iron,  so  that 
0.7  gramme  represents  0.1  gramme  of  iron.  The  mode  of  ap- 
plying it  is  as  follows: — 

0.7  gramme  of  the  salt  having  been  dissolved  in  a  beaker  in 
distilled  water,  and  five  or  six  c.  c.  of  dilute  (1  :  5).  sulphuric 
acid  added,  the  permanganate  solution  is  delivered  from  a  bu- 
rette, having  a  glass  stopcock,  until  a  point  is  reached  at  which 
the  rose  color  no  longer  disappears  on  shaking.  As  the  per- 
manganate must  be  slightly  in  excess  to  produce  a  percepti- 
ble color,  a  correction  should  be  made  by  ascertaining  experi- 
mentally how  much  of  the  salt  is  required  to  produce  the 
observed  intensity  of  color  in  the  quantity  of  liquid  used. 
This  quantity  should  then  be  deducted  from  the  result.  The 
number  of  cubic  centimetres  used  for  0.7  gramme  of  the 
double  sulphate,  (i.  e.,  0.1  gramme  of  metallic  iron)  must  be 
marked  on  the  bottle.  As  the  method  depends  on  the  con- 
version of  the  iron  from  the  lower  to  the  higher  stage  of  oxi- 
dation at  the  expense  of  the  permanganate,  it  is  obviously 
necessary  that  the  whole  of  the  iron  in  the  liquid  to  be  ope- 
rated upon  should  be  in  the  condition  (to  use  modern  lan- 
guage) of  a  ferrous  salt.  For  this  reason,  the  first  step  in 
dealing  with  the  hydrochloric  acid  solution  of  blood  ash,  is  to 
reduce  it.  With  this  view,  the  solution  of  ash  is  first  intro- 
duced into  the  flask  already  mentioned,  in  which  it  is  gently 
boiled  with  a  few  pieces  of  zinc  until  the  latter  is  dissolved 
and  the  liquid  is  colorless.  It  is  then  allowed  to  cool  and 
diluted  to  fifty  centimetres,  after  which  the  solution  of  per- 
manganate is  added  to  it  from  the  burette,  as  before,  until 
the  rose  color  becomes  permanent  after  agitation.  For  each 
centimetre  of  the  red  liquid  emplo3'ed  in  attaining  this  result, 
the  quantity  of  solution  in  the  flask  contains  0.0056  gramme 
of  iron. 


204  TIIE    BLOOD. 

Section  IV. — Gases  of  the  Blood. 

1.  The  gases  of  the  blood  are  oxygen,  carbonic  acid  and 
nitrogen.  The  knowledge  we  possess  of  the  conditions  under 
which  they  are  contained  in  the  blood,  and  of  the  relative 
quantities  of  each,  is  founded  entirely  on  the  researches  of 
Ludwig  and  his  pupils,  published  during  the  first  }rear  of  the 
last  decade. 

As  regards  ox}rgen,a  correct  method  (that  of  displacement 
by  carbonic  oxide)  had  already  been  employed  by  Claude 
Bernard  ;  but,  as  regards  carbonic  acid,  the  methods  previous- 
ly used  were  imperfect  and  the  results  erroneous. 

2.  In  round  numbers,  one  hundred  volumes  of  arterial  blood 
deliver  to  the  Torricellian  vacuum  about  twenty  volumes  of 
oxygen  (estimated  at  760  millimetres  pressure  and  0°  temper- 
ature)— venous  blood  about  twelve  volumes.  Of  the  quantity 
of  oxygen  so  extracted,  by  far  the  greatest  part  is  in  combina- 
tion with  haemoglobin — in  other  words,  in  the  concrete  state. 
The  proportion  of  free  oxygen  in  blood  is  so  small  that  oxygen 
is  absorbed  from  any  atmosphere  containing  it  in  which  its 
tension  is  greater  than  from  twenty  to  twenty -five  millimetres 
— in  other  words,  from  any  space  in  which  it  exists  in  a  pro- 
portion greater  than  about  one-eighth  of  the  proportion  in 
which  it  exists  in  the  atmosphere.  Consequently,  in  subject- 
ing blood  to  the  air-pump,  no  oxygen  is  given  off  till  the  press- 
ure sinks  to  about  125  millimetres  (t.  e.,  about  a  sixth  of  an 
atmosphere) ;  whereas,  in  the  case  of  other  liquids  (e.  g., 
water),  oxygen,  with  the  other  contained  gases,  begins  to  be 
disengaged,  pari  passu,  with  the  reduction  of  pressure,  in  a 
quantity  determinable  according  to  Dalton's  law.  These  facts 
are  expressed  by  saying  (1)  that  the  absorption  of  oxygen  by 
the  blood  is  independent  of  Dalton's  law,  and  (2)  that  the  ten- 
sion of  oxygen  in  the  blood  is  from  twenty  to  twenty-five 
millimetres  of  mercury. 

3.  When  blood  is  subjected  to  the  Torricellian  vacuum,  the 
disengagement  of  oxygen  is  complete.  The  blood  is  converted 
into  froth,  and  rapidly  assumes  a  dark  color.  This  appear- 
ance is  due  partly  to  the  discharge  of  the  coloring  matter  from 
the  corpuscles,  partly  to  the  complete  reduction  of  the  haemo- 
globin which  accompanies  the  extraction  from  the  liquor  san- 
guinis, of  its  free  oxygen. 

4.  When  blood  is  subjected  to  an  atmosphere  which  con- 
tains no  oxygen,  the  result,  so  far  as  relates  to  the  extraction 
of  oxygen,  is  the  same  as  if  it  were  exposed  to  the  vacuum. 
This  is  particularly  the  case  if  the  gas  employed  be  one  which 
has  the  power  of  combining  with  haemoglobin.  The  gas  which 
pre-eminently  enjoj's  this  faculty  is  carbonic  oxide.  When 
blood  is  subjected  to  an  atmosphere  of  this  gas,  the  oxygen  it 


BY    DR.    BURD0N-S ANDERSON.  205 

contains,  "whether  free  or  combined,  escapes  from  it,  its  place 
being  taken  by  carbonic  oxide.  The  blood-coloring  matter  in 
combination  with  this  gas  acquires  optical  and  other  characters 
which  remarkably  resemble  those  of  oxyhaemoglobin. 

5.  Carbonic  acid  gas  may  be  extracted  from  arterial  blood 
by  the  Torricellian  vacuum  in  the  proportion  of  about  35  vol- 
umes (as  estimated  at  TGO  millimetres  pressure  and  0°  tempe- 
rature) to  100  volumes  of  blood.  Venous  blood  may  yield  43 
volumes,  asphj'xial  blood  50  volumes.  Of  this  quantity  a  cer- 
tain but  very  varying  proportion  is  merely  absorbed,  the  rest 
is  in  loose  combination,  principally  with  the  sodic  carbonates 
of  the  plasma.  It  is  probable  that  some  of  it  is  held  by  the 
bibasic  sodic  phosphate  of  the  blood,  and  perhaps  some  other- 
wise. Hence  it  may  be  readily  understood  that  serum  con- 
tains as  much  carbonic  acid  gas  as  a  corresponding  volume  of 
blood. 

6.  When  a  fixed  acid,  e.  gr.,  tartaric  acid,  is  added  in  vacuo  to 
blood  which  has  been  already  deprived  of  its  absorbed  and 
loosely  combined  carbonic  acid  (which  together  constitute 
what  may  be  called  its  inexhaustible  carbonic  acid),  an  addi- 
tional quantity  of  carbonic  acid  may  be  obtained  from  it,  which 
previously  existed  in  the  blood  in  the  condition  of  neutral  car- 
bonate, principally  if  not  entirely  sodic. 

Every  apparatus  for  extracting  the  gases  of  the  blood  must 
consist  of  two  parts,  a  mercurial  pump  and  a  recipient.  The 
form  and  character  of  the  latter  necessarily  depend  upon  those 
of  the  former.  The  most  important  forms  of  pump  in  use  are 
those  of  Dr.  Geissler,  and  others  similar,  employed  in  Ger- 
many, and  of  M.  Alvergniat,  in  Paris.  In  this  country,  under 
the  direction  of  Professor  Frankland,  Mr.  Cetti  has  constructed 
a  Sprengel's  pump  for  the  purposes  of  extracting  the  gases  of 
water.  Dr.  Gamgee,  of  Edinburgh,  has  applied  this  form  of 
pump  to  the  extraction  of  the  gases  of  the  blood  with  complete 
success. 

26.  Alvergniat's  Pump. — A  long  barometer  tube,  the 
scale  of  which  is  divided  into  millimetres,  is  fixed  to  a  vertical 
board  on  a  suitable  stand.  This  tube  is  dilated  at  the  top  into  a 
large  bulb  (a,  Fig.  197),  and  is  then  continued  upwards  until  it 
ends  in  a  three-way  stopcock  (d),  surmounted  by  a  funnel.  To 
the  right,  the  stopcock  is  in  communication  with  a  glass  tube, 
ending  in  a  bulb  (jy),  and  possessing  a  flexible  joint  at/.  To 
the  lower  end  of  the  barometer  tube  is  fitted  a  long  tube  of 
thick-walled  vulcanized  caoutchouc,  which  ends  in  a  globular 
mercury-holder  (o).  The  vertical  board  is  fitted  at  regular  in- 
tervals with  perforated  shelves,  on  one  of  which  the  mercury- 
holder  is  resting.  The  pump  is  worked  as  follows:  v  having 
been  filled  with  mercury,  the  metal  enters  the  vulcanite  tube, 
and  rises  to  the  same  heijjht  in  the  tube  a  c  as  in  v.     If  v  is 


206  THK    BLOOD. 

raised  from  its  present  level  to  that  of  the  highest  of  the 
shelves,  the  stopcock  being  :it  the  same  time  turned  so  that 
the  vertical  tube  communicates  with  the  external  air.  but  not 
with  the  bulb,  the  mercury  will  rise  till  the  whole  of  the  verti- 
cal tube  is  occupied.  The  stopcock  is  now  turned  so  as  to 
make  communication  only  between  a  c  and  the  bulb,  and  the 
mercury-holder  is  replaced  in  its  original  position.  As  the  re- 
sult of  this  manipulation,  tin:  air  previously  contained  in  the 
bulb  and  the  tube  leading  from  it  occupies  the  whole  cavit}', 
and  (according  to  Marriotte's  law)  is  expanded,  i.  e.,  dimin- 
ished in  density  in  the  same  ratio  that  the  volume  occupied  by 
it  is  increased.  In  other  words,  the  density  of  the  air  in  the 
bulb,  before  the  depression  of  u,  is  to  its  density  after  as  the 
capacity  of  the  barometer  plus  the  bulb  is  to  that  of  the  bulb 
alone.  To  repeat  the  operation,  the  stopcock  must  first  be 
placed  in  such  a  position  that  all  channels  are  closed,  v  is 
then  raised  and  the  stopcock  again  turned  as  at  first — viz., 
the  horizontal  way  closed,  the  vertical  way  open.  The  ait- 
contained  in  a  c  having  been  discharged,  the  stopcock  is  again 
opened  horizontally  and  closed  vertically,  and  v  depressed. 
The  air  remaining  in  the  bulb  is  again  expanded  in  the  same 
proportion  as  before.  If  the  capacity  of  the  tube,  together 
with  its  dilatation,  be  equal  to  that  of  the  bulb  and  its  tube, 
it  is  obvious  that  the  effect  of  each  stroke  of  the  pump  will  be 
to  halve  the  density  of  the  air  in  the  bulb  ;  consequently,  if 
the  operation  is  repeated  ten  times,  the  density  of  the  air  con- 
tained in  the  bulb  (supposing  it  to  be  dry,  and  to  have  an  ori- 
ginal density  of  160  millimetres)  becomes  760x(i),0=0.74  mil- 
limetre. By  filling  the  bulb  and  the  tube  leading  to  it,  before 
attaching  it,  with  water  deprived  of  its  gases  by  boiling,  the 
process  of  exhaustion  can  be  very  much  shortened.  No  sooner 
does  the  mercury  sink  in  the  vertical  tube  (a  c)  than  the  water 
follows  it,  and  can  be  discharged  b}r  raising  the  mercury- 
holder  with  the  stopcock  open  vertically  and  closed  horizon- 
tally, as  before.  A  vacuum  which  is  almost  perfect  is  thus 
obtained  at  a  single  working  of  the  pump.  In  the  pumps 
recently  made  by  M.  Alvergniat,  he  has  substituted  a  movable 
support  which  works  up  and  down  the  vertical  board  by  a 
winch. 

27.  Geissler's  Pump — The  instrument  (see  fig.  198)  con- 
sists, like  that  just  described,  of  a  fixed  vertical  tube  (a),  which 
is  dilated  into  a  large  bulb  near  the  top  and  communicates  near 
its  lower  end  by  means  of  a  flexible  tube  of  thick  walled  caout- 
chouc with  another  vessel  (b)  which  can  be  moved  up  and  down 
by  turning  a  winch.  Above  the  bulb,  the  vertical  tube,  which 
is  nearly  a  metre  in  length,  ends  in  a  stopcock  (g),  so  con- 
structed that  the  bulb  can  be  completely  shut  off,  or  may  be 
brought  into  communication  either,  with  the  external  air  or  with 


BY    DR.    BURDON-SAXDERSON.  207 

the  cavity  to  be  exhausted.  The  pump  is  worked  in  the  same 
manner  as  that  just  described.  In  order,  if  necessary,  to  dry 
the  vacuum,  a  Pfliiger's  drying  apparatus  is  interposed  between 
the  pump  and  the  recipient.  This  may  be  described  as  a  U 
tube,  the  bend  of  which  is  dilated  into  a  bulb  (c).  It  is  so 
constructed  that  the  fragments  of  pumice  or  the  glass*  balls 
moistened  with  sulphuric  acid  which  are  used  for  drying  can 
be  readily  introduced  into  either  limb.  The  tube  leading  from 
the  dessicator  to  the  pump  communicates  with  a  vacuum  gauge 
(m).  The  advantage  which  this  instrument  possesses  consists 
in  the  relatively  large  size  of  the  bulb,  the  perfection  of  the 
workmanship  (particularly  of  the  stopcocks)  and  the  arrange- 
ment whereby  the  vacuum  obtained  is  dry. 

28.  Frankland-Sprengel  Pump—  Sprengel's  pump  as 
modified  b}r  Frankland,  consists  essentially  of  a  vertical  glass 
tube  (o  Fig.  199)  about  four  feet  long,  with  thick  walls  and  nar- 
row bore,  the  lower  end  of  which  is  bent  up  in  such  a  way  that, 
if  filled  with  mercury,  and  closed  at  the  top,  it  would  constitute 
a  barometer.  At  its  upper  end,  however,  it  is  not  closed,  but 
is  continuous  by  a  bend  with  the  second  vertical  tube  (g)  or 
ascending  limb  of  the  Sprengel  (the  supply  tube),  which  is  of 
wider  bore,  and  runs  parallel  to  the  first.  At  the  top,  or  con- 
vexity of  the  bend,  a  third  tube,  about  four  inches  in  length 
(the  exhaustion  tube),  is  sealed  on,  by  which  the  barometer 
tube  or  descending  limb  communicates  with  the  cavity  to  be 
exhausted.  The  ascending  limb  communicates  by  a  flexible 
tube,  strengthened  by  a  covering  of  strong  canvass  and 
guarded  by  a  screw  clip,  with  the  descending  limb  of  another 
bent  tube  (c)  of  similar  construction  to  the  first;  the  only  dif- 
ference between  it  and  the  one  just  described  being  that  it  com- 
municates at  the  bend,  not  with  any  cavity,  but  merely  with  a 
bulb  (d)  closed  at  E  by  mercury.  Its  other  limb  finally  com- 
municates by  a  second  flexible  tube  with  a  reservoir  of  mer- 
cury (b),  the  arrangement  of  which  will  be  best  understood  from 
the  figure.  It  consists  of  two  glass  funnels,  each  having  long 
stems,  the  relative  sizes  of  which  are  such  that  the  one  can  be 
contained  within  the  other.  To  work  the  pump,  the  exhaust- 
ing tube  of  the  first  bent  tube  must  be  connected  with  the  cavit}' 
to  be  exhausted  by  means  of  a  junction  of  vulcanized  caout- 
chouc, guarded  by  a  chamber  filled  with  glycerin.  Mercui^  is 
then  poured  into  the  inner  funnel  (the  tube  leading  to  the  first 
bend  having  been  previously  closed)  until  it  rises  in  the  space 
between  it  and  the  outer  to  the  same  level.  This  done,  the 
clip  is  opened,  and  a  stream  of  mercury  is  allowed  to  flow  over 
the  two  bends  in  succession,  great  care  being  taken  that  the 
stream  is  not  so  abundant  as  to  cause  the  mercury  to  ascend 
in  tin;  exhausting  tube  above  the  level  of  the  bend.  The  flow 
must  then  be  gradually  diminished  with  the  aid  of  the  clip, 


208  TIIE   BLOOD. 

until  the  column  of  mercury  in  the  descending  limb  of  the 
Sprengel  tube  is  broken  into  fragments  by  intervening  spaces 
containing  air.  This  happens  whenever  the  quantity  of  mer- 
cury which  readies  the  bend  by  the  ascending  limb  in  any  given 
time,  is  less  than  that  which  leaves  it  by  the  descending  limb. 
In  a  time  which  varies  according  to  the  capacity  of  the  cavity 
to  be  exhausted,  vacuum  is  attained.  No  more  bubbles  are 
discharged  at  the  lower  end  of  the  Sprengel.  Each  drop  of 
mercury  as  it  falls  produces  a  peculiar  click,  and  if  the  current 
is  stopped,  it  is  seen  that  the  height  of  the  column  in  the  de- 
scending limb  is  less  than  that  of  the  barometer  at  the  time, 
by  a  number  of  millimetres  which  is  equal  to  the  tension  of 
aqueous  vapor  at  the  temperature.  The  apparatus  is  so 
arranged  that  the  bend  of  the  first  tube  is  supported  at  a  level 
several  inches  higher  than  that  of  the  second.  Consequently, 
as  the  process  of  exhaustion  approaches,  the  bulb  with  which 
it  communicates  becomes  emptied  of  mercury,  the  vacuous 
space  thus  formed  gradually  extending  till  the  level  of  the  mer- 
cury in  the  descending  limb  coincides  with  that  of  the  bend  of 
the  second  tube. 

We  next  pass  to  the  description  of  the  method  of  obtaining 
blood  from  an  artery  or  vein,  and  of  transferring  it  to  the 
vacuum.  Although  it  is  not  possible  to  produce  a  vacuum 
with  the  Sprengel  pump  above  described,  as  rapidly  as  with 
the  ordinary  mercurial  pump,1  its  action  in  other  respects  is 
very  satisfactory.  It  completely  fulfils  the  conditions  enume- 
rated by  Ludwig  as  essential  to  an  efficient  blood-pump.  The 
vacuum  produced  is  perfect;  it  is  bounded  by  mercury  which, 
having  previously  passed  through  a  vacuum  (in  the  first  tube), 
is  completely  deprived  of  air;  and  it  can  be  renewed  any  num- 
ber of  times  after  the  blood  is  introduced. 

29.  Method  of  Transferring  the  Blood  to  be  Ex- 
hausted from  the  Artery  or  Vein  to  the  Vacuum. — It 
is  essential  that  the  transference  should  be  effected  without 
contact  with  air;  the  blood  must  therefore  either  flow  as  directly 
as  possible  from  the  artery  or  vein  into  the  vacuum  tube:  or, 
if  it  is  intended  to  de  fibrin  ate  it,  it  must  be  received  in  a  space 
previously  occupied  by  mercury.  Before  describing  the  mode 
of  transferring,  an  account  must  be  given  of  the  chamber  or  re- 
cipient in  which  the  blood  is  exhausted,  and  of  tiie  mode  in 
which  it  communicates  with  the  pump.  The  exhaustion  tube 
(sec  Fig.  199,  ii)  is  connected  by  a  vulcanite  union,  inclosed  in 
an  external  tube  containing  glycerin,  with  a  long  nearlj'  capil- 
lary tube,  of  such  form  and  length  as  to  reach  the  table  by  the 
side  of  which  the  pump  stands.     Near  its  lower  end  it  is  bent 

1  The  instrument  probably  admits  of  considerable  improvement  in  this 
respect. 


BY    DR.    BURDON-SANDERSON.  209 

at  an  obtuse  angle,  so  that  the  last  few  inches  are  horizontal. 
A  little  above  the  bend  there  is  a  bulb:  the  horizontal  part  is 
firmly  supported  on  a  block.  With  this  tube  the  recipient  is 
united  either  by  a  mercurial  joint  (i)  or  by  a  connector  of  vul- 
canized India-rubber,  inclosed  in  a  glycerin  chamber.  The 
recipient  is  a  large  glass  tube  (j),  of  about  an  inch  and  a 
quarter  diameter,  and  forty  inches  long.  At  its  lower  end  it 
terminates  in  a  capillar}'  tube,  which  is  guarded  by  a  stopcock 
(l).  Its  capacitj'  is  about  250  centimetres,  consequently  six- 
teen times  that  of  the  blood  it  is  intended  to  receive. 

In  selecting  a  method  of  transference,  preference  ought  to  be 
given  to  those  plans  which  are  least  complicated  and  most  rapid 
in  execution.  The  method  I  have  found  to  answer  is  as  fol- 
lows: The  animal  having  been  secured,  a  canula  fitted  with  an 
India-rubber  connector  is  inserted  in  the  vessel,  which  is  closed 
by  a  clip  lege  artis.  For  receiving  the  blood  as  it  flows  from 
the  artery  or  vein,  a  straight-glass  tube  (Fig.  199,  m)  of  known 
capacity  is  used ;  one  end  of  this  tube  is  guarded  b\'  a  stop- 
cock, while  the  other  is  drawn  out,  and  so  formed  that  it  can 
be  accurate!}'  stopped  by  the  finger.  A  trough  having  been 
filled  with  mercury,  completely  freed  from  air  by  passing 
through  the  pump,  the  narrow  end  of  the  tube  is  dipped  into 
it.  The  tube  is  then  easily  filled  up  to  the  stopcock  by  aspira- 
tion and  the  stopcock  closed.  It  having  been  ascertained  that 
the  tube  is  perfectby  full,  it  is  placed  in  an  inclined  position, 
with  the  stopcock  end  downwards,  and  the  open  end  at  such  a 
distance  from  the  canula  that  the  India-rubber  tube  can  be 
easily  slipped  over  it  at  the  required  moment.  This  having 
been  accomplished,  and  the  other  end  of  the  tube  having  been 
fitted  with  a  bit  of  India-rubber  tubing  of  sufficient  length  to 
conve}'  away  the  mercury  to  a  convenient  receptacle,  all  is 
ready.  The  clip  on  the  canula  is  opened,  and  blood  allowed  to 
flow  freely  from  the  tube  for  a  few  moments  while  the  mercuiy 
tube  is  grasped  by  the  operator.  The  warmth  of  the  hand 
causes  the  mercury  to  expand  and  project  from  the  open  end 
of  the  tube:  at  that  moment  the  India-rubber  connector  from 
which  blood  is  flowing  is  slipped  over  it,  and  the  connection  is 
completed  without  the  slightest  risk  of  the  introduction  of  air. 
Withont  a  moment's  loss  of  time  the  stopcock  is  opened,  and 
the  blood  allowed  to  replace  the  mercury.  The  stopcock  having 
been  closed,  the  India-rubber  connector  is  slipped  off,  and  the 
open  end  of  the  tube  closed  with  the  finger.  The  tube  is  now 
placed  with  its  open  end  downwards  in  the  mercurial  trough 
(u  i,  the  finger  being  still  kept  on  the  orifice,  while  an  assistant 
fills  the  bit  of  capillary  tube  beyond  the  stopcock  with  boiled 
distilled  water,  and  connects  it  with  the  corresponding  end  of 
the  recipient  by  means  of  an  India-rubber  connector.  The  mo- 
ment that  this  is  accomplished,  the  finger  is  removed  from  the 
14 


210  THE   BLOOD. 

orifice  of  the  tube,  and  both  stopcocks  are  opened.  The  blood 
passes  rapidly  into  the  recipient,  followed  by  a  column  of  mer- 
cury, and  is  at  once  converted  into  froth.  A  few  drops  of  mer- 
cury having  been  allowed  to  enter,  the  stopcocks  are  finally 
closed.  It  will  be  understood  from  the  figure  that  the  joint 
between  the  measuring  tube  and  the  recipient,  as  well  as  the 
stopcocks,  are  under  water,  the  purpose  of  which  arrangement 
is,  it  need  scarcely  be  said,  to  obviate  the  risk  of  the  entrance 
of  air. 

At  first  the  water  in  the  wooden  trough  (n,  which  is  not  in- 
troduced until  M  has  been  joined  to  l)  is  kept  cool  with  frag- 
ments of  ice,  in  order  to  prevent  the  blood  from  coagulating 
during  the  preliminary  operations.  As  soon  as  all  is  complete, 
hot  water  is  graduall}'  added  until  the  temperature  rises  to 
about  40°  C,  care  being  taken  not  to  expose  the  stopcocks  to 
the  air  during  the  process.  The  only  moment  in  the  process 
at  which  air  can  be  admitted,  is  that  of  joining  the  measuring 
tube  to  the  recipient.  For  this  reason  it  is  desirable,  before 
opening  the  second  stopcock  of  the  measuring  tube,  to  keep  the 
pump  in  action  for  a  few  minutes  so  as  to  be  certain  that  the 
vacuum  is  unimpaired  before  admitting  the  blood.  This  is  not- 
attended  with  inconvenience,  ifthe  blood  is  kept  at  a  tempera- 
ture approaching  that  of  freezing. 

When  it  is  desired  to  defibrinate  the  blood  before  exhausting 
it,  it  must  be  collected  over  mercury.  This  is  best  effected  in 
Ludwig's  recipient.  This  recipient  is  a  tube  closed  at  one  end 
and  furnished  with  a  Geissler's  stopcock  having  a  remarkably 
large  way.  The  tube  is  inverted  over  mercury,  with  the  stop- 
cock open,  and  the  blood  allowed  to  flow  directly  from  the  ves- 
sel into  it  until  it  is  nearl}7  filled.  It  is  then  closed  by  the  hand, 
defibrinated  by  vigorous  shaking  with  mercury,  and  replaced 
in  the  trough.  The  stopcock  is  now  closed,  and  the  tube,  from 
which  the  blood  contained  outside  of  the  stopcock  has  been 
washed,  is  united  with  the  recipient  of  the  pump  by  an  India- 
rubber  joint.  To  carry  out  this  method,  Sprengel's  pump  is 
scarcely  applicable  ;  for,  inasmuch  as  the  process  of  exhaustion 
cannot  be  begun  until  the  connection  is  made,  a  long  time  must 
elapse  before  the  tap  can  be  opened.  Blood  alters  so  rapidly 
after  removal  from  the  body — the  oxygen  diminishing,  the  car- 
bonic acid  increasing — that  if  much  time  is  lost  the  results  are 
of  little  value. 

30.  Method  of  Analysis. — In  France  most  of  the  analy- 
ses which  have  been  published  by  Bernard  and  his  pupils  have 
been  made  by  a  method  which,  although  rapid,  is  inexact.  In 
Germany  the  analyses  of  Ludwig  and  his  pupils,  as  well  as 
those  of  Pfliiger,  have  been  made  according  to  the  accurate 
methods  first  introduced  by  Bunsen,  and  commonly  known  by 
his  name.     Bernard's  method  is  practised  in  the  physiological 


BY   DR.    BURDON-SANDERSON.  211 

laboratory  of  the  Jardin  des  Plantes,  in  Paris.  The  analysis 
is  made  in  a  circular  mercurial  trough,  in  the  centre  of  which 
is  a  well  sixteen  inches  deep,  and  large  enough  to  contain 
about  12  lbs.  of  mercury.  The  gas  having  been  transferred 
from  the  tube  in  which  it  is  collected  from  the  pump,  to  a 
eudiometer,  the  latter  is  plunged  into  the  mercury,  in  order 
that  its  contained  air  may  acquire  the  temperature  of  the 
metal.  It  is  .then  raised  with  the  aid  of  a  wooden  tube-holder 
until  the  level  of  the  mercuiy  inside  is  the  same  as  that  out- 
side. The  quantity  of  gas  having  been  measured,  a  fragment 
of  caustic  potash  is  introduced,  which  rapidly  dissolves  in  the 
few  drops  of  water  which  always  float  on  the  surface  of  the 
mercury.  The  column  of  mercury  is  then  gentty  agitated  by 
alternately  raising  and  lowering  the  eudiometer,  which,  after 
the  completion  of  absorption,  is  again  plunged  into  the  mercury. 
The  gas  having  been  again  measured,  about  a  centimetre  of 
strong  solution  of  pyrogallic  acid  is  introduced  with  the  aid 
of  a  pipette  with  a  bent  beak.  The  agitation  is  repeated  and 
continued  for  some  time.  As  soon  as  the  absorption  of  the 
ox}Tgen  appears  to  be  complete,  the  tube  is  transferred  to  a 
basin  containing  water,  into  which  the  mercury  with  the  pyro- 
gallate  of  potash  is  allowed  to  fall.  The  residue,  consisting  of 
nitrogen,  is  read  over  water.  The  results  obtained  by  this  rough- 
and-ready  method  must  necessarily  be  erroneous,  not  only  be- 
cause the  measurements  are  inaccurate,  but  because  the  absorp- 
tions must  always  be  incomplete.  If,  however  (as  in  certain 
pathological  inquiries),  it  is  more  important  that  the  analy- 
ses should  be  numerous  than  that  they  should  be  exact,  it  may 
be  available.  For  class  illustrations  of  the  general  nature  of 
the  blood  gases,  it  is  completely  adapted. 

For  more  exact  purposes  the  process  of  gas  analysis  has 
been  during  the  last  few  years  much  shortened  by  Frankland, 
Russell,  and  others.  With  a  view  to  the  analysis  of  the  gases 
of  drinking  water,  Frankland  has  introduced  an  apparatus  of 
great  simplicity  (see  Fig.  200),  the  working  of  which  will  be 
readily  understood  by  the  diagram.  It  consists  of  two  parts, 
viz.,  a  laboratory  tube  (&),  in  which  the  gas  to  be  analyzed  is 
first  received,  and  a  measuring  apparatus  to  which  it  can  be 
transferred  from  the  laboratory,  in  order  that  its  volume  may 
be  determined  before  and  after  each  absorption.  The  measur- 
ing apparatus  consists  of  two  tubes  (a,  6),  fixed  vertically  side 
by  side  in  a  stand,  surrounded  by  a  chamber  containing 
water  (n).  They  communicate  below  both  with  each  other 
and  (by  the  long  flexible  tube)  with  a  mercury-holder  (t),  like 
that  of  Alvergniat's  pump.  One  of  them  can  be  brought  into 
communication  by  the  arm  (g)  with  the  laboratory  tube  ;  the 
other  (b)  is  open  at  the  top.  A  scale  of  millimetres  is  en- 
graved on  it,  the  zero  of  which  is  opposite  o.     A  corresponding 


212  THE    BLOOD. 

scale,  starting  from  a  zero  at  the  same  level,  is  engraved  on 
the  measuring  tube.  The  apparatus  is  filled  with  mercury  by 
raising  the  mercurj'-holder  (/)  to  a  sufficient  height,  the  stop- 
cock (f)  remaining  open  ;  in  doing  which  the  surface  of  the 
mercury  in  t  must  not  be  more  than  a  few  millimetres  higher 
than  the  tap.  As  soon  as  the  mercury  appears  at  g,  the  stop- 
cock is  closed.  The  next  step  is  to  fill  the  laboratory  tube. 
Having  inverted  it  in  the  trough,  which  has  been  previously 
raised  to  the  proper  height,  the  operator  draws  out  most  of 
the  air  by  means  of  a  bent  tube,  the  point  of  which  rises  to 
the  top  of  the  laboratory  tube,  and  shuts  the  stopcock  as  soon 
as  the  mercury  rises.  The  removal  of  the  air  is  completed  by 
joining  g  and  g'  so  as  to  connect  the  laboratory  tube  with  the 
measuring  apparatus,  and  then  causing  the  air  contained  in 
the  former  to  pass  over  into  the  latter,  by  depressing  t.  The 
stopcock  h  must  now  be  closed  and  g  and  g'  disconnected  to 
allow  of  the  expulsion  of  the  air  from  a.  This  having  been 
accomplished,  g  and  g'  are  again  brought  together  and  care- 
fully secured.  The  whole  apparatus  is  now  full  of  mercury  ; 
as  soon  as  it  has  been  ascertained  that  the  joint  is  air-tight  at 
all  pressures,  it  is  ready  for  use.  Before  proceeding  further, 
however,  the  measuring  tube,  which,  as  already  stated,  is 
graduated  in  millimetres  measured  from  an  arbitrary  zero  line 
near  the  bottom,  must  be  calibrated.  In  other  words,  it  must 
be  ascertained  as  regards  each  principal  mark  of  the  gradu- 
ation, what  volume  of  air  or  water  (as  the  case  may  be)  the 
tube  contains,  when  the  upper  convex  surface  of  the  mercury 
stands  exactly  level  with  it.  For  this  purpose  the  orifice  a  is 
connected  by  means  of  an  India-rubber  tube  with  a  reservoir 
(a  funnel)  containing  distilled  water.  The  mercurial  column 
is  then  allowed  to  descend  until  it  stands  exactly  at  zero.  A 
weighed  beaker  having  been  then  placed  under  a,  water  is  ex- 
pelled till  the  column  stands  at  a  height  of  fifty  millimetres, 
and  the  beaker  again  weighed.  In  a  similar  manner  the  out- 
flow of  water  corresponding  to  a  rise  of  the  mercurial  column 
from  fifty  to  one  hundred  millimetres  is  determined,  until  the 
capacit}'  which  corresponds  to  each  fiftj'  millimetres  of  the 
scale  is  ascertained.  To  insure  accuracy',  the  process  must  be 
repeated  several  times.  If  the  results,  after  correction  for 
difference  of  temperature,  are  in  close  accordance,  the  means 
may  then  be  taken  as  expressing  the  capacities  required.  In 
the  upper  part  of  the  tube,  calibration  must  be  made  at  short- 
er intervals.  In  calibrating,  as  in  all  subsequent  measure- 
ments, the  height  of  the  column  must  be  read  horizontally 
through  a  telescope,  so  adjusted  that  its  axis  is  at  the  same 
height  as  the  surface  of  the  mercury.  The  temperature  is 
read  by  a  thermometer  suspended  in  the  cylinder  of  water  by 
which  the  barometer  and  measuring:  tube  are  surrounded. 


BY  DR.  BURDON-S ANDERSON.  213 

31.  Introduction  of  the  Gas  to  be  Analyzed. — The 

measuring  and  laboratory  tubes  having  been  brought  into  con- 
nection in  the  manner  described  above,  and  both  filled  with 
mercury,  the  gas  to  be  analyzed  is  introduced  into  the  labo- 
ratory tube  from  the  test  tube  to  which  it  has  been  discharged 
b}7  the  Sprengel.  It  is  then  at  once  transferred  to  the  mea- 
suring tube  by  depressing  t  until  the  mercury  rises  in  the 
laboratory  tube  as  far  as  the  stop-cock  g'.  This  done,  the 
stop-cock  g  is  closed,  and  t  raised  or  depressed  till  the  column 
stands  at  one  of  the  marks  of  the  graduation,  in  reference  to 
which  the  capacity  of  the  tube  has  been  determined.  The 
temperature  is  then  observed,  and  the  pressure  determined  by 
adding  the  difference  between  the  height  of  the  column  in  the 
measuring  tube  and  that  in  the  pressure  tube,  to  the  reading 
of  a  barometer  which  stands  by.  A  few  drops  of  solution  of 
caustic  potash  having  been  introduced  into  the  laboratory 
tube,  the  gas  is  returned  from  the  measuring  tube.  Absorption 
takes  place  rapidly.  It  is  accelerated  by  slightly  agitating  the 
trough,  and  by  allowing  the  mercury  to  stream  into  the  labo- 
ratory tube  after  the  gas  has  passed.  The  measurement  of 
the  gas  after  absorption  is  performed  in  the  same  manner  as 
before.  About  half  a  centimetre  of  strong  solution  of  pyro- 
gallic  acid  is  then  introduced  in  the  same  way  as  the  potash, 
and  the  gas  again  returned.  After  absorption  of  the  oxj'gen, 
what  remains  is  nitrogen.  In  analysis  of  blood  gases,  the 
proportion  of  nitrogen  is  nearly  constant,  viz.,  about  2.5  vol- 
umes in  100  volumes  of  blood.  If  a  larger  quantity  is  obtained, 
the  fact  indicates  that  air  has  entered.  Whatever  method  of 
analysis  is  employed,  the  results  must  be  reduced  to  0°  tem- 
perature and  760°  millimetres  pressure — t.  e.,  they  must  be 
expressed  as  if  the  measurements  had  been  made  under  those 
conditions.  A  further  deduction  must  be  made  from  each 
measurement  in  respect  of  the  aqueous  vapor  which  the  gas 
contains  (the  measuring  tube  being  always  moist).  This  is 
accomplished  by  the  following  well-known  formula  : — 

v  =    J!_ H'-/ 

1    +   t  0-00367  760 

V  denotes  the  corrected  volume;  V  the  volume  read;  t  the 
temperature;  H'  the  observed  pressure;  and  f  the  tension  of 
aqueous  vapor  at  the  temperature  t.  The  values  of  1  -f  t  0.003G7 
and  /  are  always  obtained  from  tables.  For  these,  and  many 
other  important  practical  details  relating  to  the  performance 
of  gas  analysis,  the  reader  is  referred  to  Mr.  Sutton's  "  Volu- 
metrical  Analysis,''  whom  I  have  to  thank  for  two  of  the 
woodcuts  with  which  this  section  is  illustrated.  To  illustrate 
the  application  of  the  method  to  the  analysis  of  the  gases  of 
the  blood,!  give  the  following  example:  — 


214 


TIIL    BLOOD. 


Analysis  of  Gases  of  Arterial  Blood  of  Dog. 


2d  Measurement 

1st  Measure nt. 

After  absorption 

.'id  Measurement. 

Total    quantity 

of  carbonic  acid 

After  absorption 

of  gas  extracted. 

gas, 

of  oxygen. 

Height  of  column  in  measur- 

ing-tube 

230.0 

270.0 

450.0 

Height  of  column    in   pres- 

sure-tube 

312.8 

369.0 

320.0 

Difference 

82.8 

99.0 

—130.0 

Reading  of  barometer 

7G4.0 
846.8 

764.0 

764.0 

H'= 

863.0 

634.0 

Tempcrature=19.8°C.=t. 

Tension  of  aqueous   vapors 

from  table=f= 

17.2 

17.2 
845.8 

17.2 

H'— f= 

829.6 

626.8 

Volume  of  gas  as  measured 

in  cubic  centimetres=V  — 

11.822 

3.865 

0.562 

1  +  t  0.00367  (from  table) 
Hence  from  the  first  measurement  we  have — 
11.822        829.6 


1.0725. 


V  = 


V. 


1.0725 

From  second  measurement — 
3.865 
1.0725  ' 
From  third  measurement — 
y         0.562 


760 

845.8 


=  12.030. 


760 


=  4.010. 


626.8 


=  0.432. 


1.0725     760 

Thus  the  total  volume  of  gases  obtained  as  measured  at  0°  C. 
and  760  in.  m.  was  12.030  cubic  centimetres  ;  of  carbonic  acid 
gas  was  12.030  —  4.010  =  8.02  c.  c.;  of  oxygen  4.010  —  0.432  = 
3.578  c.  c,  and  of  nitrogen  0.432  c.  c. 

As  the  volume  of  blood  employed  was  20.266  cubic  centime- 
tres, we  have  the  following  final  result : — 

In  100  volumes  of  blood — 


Carbonic  acid  <^as  39.585  volumes 


8.020 


Oxygen 
Nitrogen 

Total 


17.652 


2.138 


59.375 


0.20266 
3.578 

0.20266 
0.432 

0.20266 
12.030 

0.20266 


(= 


vols. 


vols. 


vols. 


vols. 


BY    DR.    BURB-ON-SANDERSON.  215 

In  the  preceding  example  such  variations  of  temperature 
and  barometric  pressure  as  may  occur  during  the  analysis  are 
disregarded.  The  readings  are  taken  immediately  after  the 
absorption  of  the  carbonic  acid  gas ;  as  the  time  occupied  in 
the  analysis  up  to  this  point  is  very  short,  the  error  arising 
from  the  variations  in  question  is  inconsiderable.  As  regards 
the  absorption  of  oxygen,  the  error  might  be  of  more  conse- 
quence, were  it  not  that  the  residue  of  nitrogen  is  so  small. 
As  it  is,  it  can  be  easiljr  shown  that  it  would  require  a  differ- 
ence of  pressure  amounting  to  three  millimetres,  and  a  dif- 
ference of  a  degree  of  temperature,  to  make  an  error  of  one- 
hundredth  of  a  percentage  in  the  result  as  regards  nitrogen  or 
oxygen.  Within  these  limits,  therefore,  the  errors  arising  from 
this  source  may  be  regarded  as  trivial. 

Although  determinations  of  oxygen  made  by  absorption 
with  hydrate  of  potash  and  pyrogallic  acid  are  not  entirely 
free  from  objection  on  the  score  of  accuracy,  the  results  ob- 
tained by  the  method  above  described  are  quite  accurate  enough 
for  most  of  the  purposes  of  physiological  research,  for  the  small 
errors  are  practically  inappreciable,  as  compared  with  the  varia- 
tions hi  the  proportion  of  oxygen  contained  in  the  blood  to  be 
analyzed,  produced  by  what  might  be  regarded  as  very  trifling 
differences  in  the  mode  of  collecting  it.  If  it  is  desired  to  have 
recourse  to  explosion  with  hydrogen,  the  best  methods  for  the 
purpose  are  those  of  Dr.  W.  Russell,  and  of  Frankland,  and 
Ward.  The  following  short  description  of  the  latter  will  be 
readily  understood  from  what  has  preceded.  The  apparatus 
(Fig.  201)  consists  of  two  parts,  corresponding  to  the  labora- 
toiy-tube  and  measuring-tube  of  the  instrument  previously  de- 
scribed. The  measuring-tube  communicates,  as  in  that  instru- 
ment, with  a  second  tube  (the  one  most  to  the  right  in  the 
figure)  containing  a  column  of  mercury,  by  the  height  of  which 
the  pressure  to  which  the  gas  to  be  measured  is  subjected,  can 
be  estimated.  The  chief  difference  is  that,  whereas  in  the  for- 
mer more  simple  instrument  the  pressure-tube  is  open  at  the 
top,  so  that  if  air  is  contained  in  the  measuring-tube,  and  the 
stopcock  by  which  it  communicates  with  the  laboratory-tube 
is  closed,  the  difference  between  the  heights  of  the  two  columns 
indicates  the  difference  between  the  tension  of  the  gas  in  the 
measuring-tube  and  that  of  the  atmosphere;  in  the  instrument 
now  before  us  the  tube  is  closed,  and  constitutes  a  barometer, 
so  that  the  difference  expresses  the  actual  tension  of  the  gas  in 
inches  of  mercury.  In  the  horizontal  channel,  by  which  the 
measuring-tube  and  barometer  communicate  at  the  bottom,  is 
a  three-way  stopcock  (not  shown  in  the  figure),  by  which  they 
may  lie  brought  into  communication  cither  with  a  vertical 
escape-tube,  the  end  of  which  dips  into  a  receptacle  containing 
mercury  several  feet  below,  or  with  a  tube  open  at  the  top  (the 


216  THE    BLOOD. 

middle  and  longest  in  the  figure),  called  the  filling-tube.  In 
this  way  the  gas  can  be  expanded  or  compressed  at  the  will  of 
the  operator,  and  consequently  can  (in  most  analyses)  be 
readily  brought  to  the  same  volume  after  each  successive  ope- 
ration. The  convenience  of  this  is  very  great,  for  obviously 
the  tensions  of  different  quantities  of  gas  when  expanded  to 
the  same  volume  are  proportional  to  the  volumes  they  would 
assume  if  they  were  all  under  the  same  pressure,  so  that  the 
original  volume  of  gas  to  be  analyzed  being  known,  the  rela- 
tion between  that  volume  and  the  volume  of  the  other  quanti- 
ties to  be  measured  can  be  readily  calculated,  the  several  vol- 
umes being  proportional  to  the  corresponding  readings  of  the 
barometer.  The  original  volume  of  gas  to  be  analyzed  is  mea- 
sured as  before  described,  with  this  difference,  that  the  absolute 
pressure  to  which  it  is  exposed  is  known  without  reference  to 
the  barometric  pressure  outside  at  the  time.  The  explosion  is 
effected  in  the  eudiometer,  into  the  upper  end  of  which  two 
platinum  wires  are  fixed  for  the  purpose  ;  the  arrangement  of 
these  wires  is  the  same  as  in  Bunsen's  eudiometer.  As  to  the 
mode  of  preparing  and  introducing  pure  hjdrogen,  and  of  ex- 
ploding the  mixture,  the  reader  will  find  sufficient  information 
in  Roscoe's  translation  of  Bunsen's  Gasometry. 

32.  Bernard's  Method  of  Determining  the  Propor- 
tion of  Oxygen  combined  "with  the  Coloring  Matter 
of  the  Blood  by  Displacement  with  Carbonic  Oxide. — 
As  was  before  stated,  the  property  which  carbonic  oxide  pos- 
sesses of  displacing  the  oxygen  combined  with  the  coloring 
matter  of  the  blood,  has  been  used  by  Bernard,  as  a  substitute 
for  the  vacuum,  for  the  determination  of  the  quantity  of  free 
and  combined  oxygen  contained  in  the  blood.  Bernard's 
-method  consists  in  agitating  the.  blood  to  be  analyzed  in  a 
tube  half  filled  with  carbonic  oxide.  The  carbonic  oxide  to  be 
used  must  be  perfectly  pure.  The  tubulated  retort  into  which 
the  oxalic  and  sulphuric  acid  are  introduced  must  l>e  cleared 
of  atmospheric  air,  by  passing  a  stream  of  carbonic  acid 
through  it,  before  heat  is  applied.  The  gas  is  best  collected 
in  flasks,  over  water  containing  potash  in  solution.  Two  re- 
sults are  produced.  In  the  first  place,  the  oxygen  of  the  hae- 
moglobin is  replaced  by  cai'bonic  oxide  ;  and,  secondly,  the 
atmosphere  of  carbonic  oxide  acts  on  the  blood  as  if  it  were  a 
vacuum,  the  displaced  oxygen  and  other  gases  passing  out 
into  it  until  equilibrium  is  established.  Inasmuch  as  the  pro- 
portion in  wdiich  oxygen  is  absorbed  is  very  small,  as  com- 
pared with  the  quantity  held  in  combination  by  haemoglobin, 
nearty  the  whole  is  discharged,  so  that  if  the  proportion  of 
that  gas  contained  in  the  gaseous  mixture  which  fills  the  place 
originally  occupied  by  the  carbonic  oxide  be  determined,  it  is 
found  to  fall  very  little  short  of  the  proportion  obtained  from 


BY  DR.  BURDON-S ANDERSON.  217 

the  same  blood  by  exhaustion.  The  remainder  of  the  mixture 
contains,  in  addition  to  the  excess  of  carbonic  oxide,  nitrogen 
and  carbonic  acid  gas,  derived  from  the  blood,  but  the  propor- 
tions of  these  gases  discharged  are  very  variable.  As  regards 
oxvgen,  the  method  has  yielded,  in  the  hands  of  Bernard,  re- 
sults of  the  greatest  value.  It  has  the  immense  advantage 
that  it  can  be  carried  out  without  a  mercurial  pump,  and  for 
pathological  purposes  is  sufficiently  accurate. 


CHAPTER  XVI. 

THE  CIRCULATION  OF  THE  BLOOD. 

In  commencing  the  study  of  the  circulation  of  the  blood,  it 
is  desirable  to  direct  our  attention  first  to  that  part  of  the 
circulatory  apparatus  in  which  the  phenomenon  presents  itself 
in  its  simplest  form.  In  systematic  physiological  treatises  the 
heart  is  usually  described  first;  but  for  our  present  purpose, 
considering  that  the  heart  is  an  organ  of  very  complicated 
structure,  that  it  is  constantly  influenced  by  ever-varying 
conditions  of  the  vessels  on  the  one  hand,  and  of  the  nervous 
centres  on  the  other,  it  is  much  better  to  begin  with  the 
arterial  system. 

Part  I The  Arteries. 

At  the  commencement  of  the  period  of  relaxation  of  the 
heart — t.  e.,  of  the  period  which  intervenes  between  one  con- 
traction and  its  successor — the  progressive  movement  of  the 
blood  in  the  aorta  all  but  ceases.  At  that  moment,  and  during 
the  remainder  of  the  time  which  precedes  the  bursting  open 
of  the  aortic  valve,  the  pressure  exercised  by  the  wall  of  the 
vessel  on  its  contents  is  the  only  cause  of  the  continuance  of 
the  blood-stream.  During  each  ventricular  systole  the  aortic 
pressure  is  reinforced  by  the  motion  communicated  to  the 
blood  by  the  contracting  ventricle.  Consequentl}',  if,  for  the 
sake  of  facilitating  our  understanding  of  the  matter,  we 
assume  the  heart  to  be  a  mere  pump,  acting  regular^,  and 
discharging  at  each  stroke  an  invariable  quantity  of  liquid,  we 
have  the  force  by  which  the  circulation  is  carried  on  at  any 
moment  expressed  by  the  tension  of  the  arteries,  and  varying 
with  that  tension;  or  if,  on  the  other  hand,  we  assume  the 
tension  of  the  arterial  system  to  remain  constant,  then  the 
quantity  of  work  done  varies  with  the  mean  velocity  of  the 


218  CIRCULATION   OF   THE    BLOOD. 

stream  at  the  commencement  of  the  aorta — in  other  words, 
with  the  quantity  of  blood  delivered  by  the  heart  per  minute. 
The  work  done  by  the  heart  in  maintaining  the  circulation, 
manifests  itself  in  the  aorta  in  two  modes,  those  of  pressure 
and  progressive  motion  of  the  blood.  These  two  phenomena 
are  not,  however,  collateral  results,  i.  e.,  they  do  not  stand  in 
the  same  relation  to  the  agent  which  produces  them.  The 
former  is  rather  the  efficient  cause  of  the  latter;  for  so  long 
as  the  arterial  pressure  continues,  i.  e.,  so  long  as  the  pressure 
in  the  aorta  is  greater  than  that  in  the  vense  cava*,  progressive 
movement  also  continues.  As  soon  as  equilibrium  is  estab- 
lished, circulation  stops.  Systemic  death  consists  in  decline 
of  aortic  pressure.  This  decline  may  occur  rapidly,  as  in 
syncope ;  but  usually,  even  in  deaths  by  violence,  it  is  very 
gradual.  In  deaths  from  disease  it  may  last  for  days,  weeks, 
or  even  months. 

Section  I.— Arterial  Pressure. 

33.  The  arterial  pressure,  although  in  the  mean  remarkably 
constant,  almost  as  constant  as  the  temperature  of  the  body, 
is  subject  to  recurring  variations — ?'.  t?.,  alternate  augmenta- 
tions and  diminutions,  which  are  of  three  orders.  Of  these, 
the  first  is  dependent  on  the  rhythmical  injection  of  blood  into 
the  arteries  by  the  contraction  of  the  heart ;  the  second,  on  the 
influence  which  the  respiratory  movements,  or  rather  the  alter- 
nate acts  of  breathing,  exercise  on  the  circulation;  the  third, 
on  augmentations  or  diminutions  of  what  is  called  the  tonus  of 
the  arteries,  by  virtue  of  which  they  are  constantly  undergoing 
changes  of  diameter,  consequent  on  varying  conditions  of  the 
nervous  system. 

In  the  measurement  of  the  arterial  pressure  we  have,  there- 
fore, two  distinct  problems.  The  first  is  the  determination  of 
the  mean  or  average  pressure,  which,  as  I  have  said  before,  is 
almost  as  constant  as  the  temperature  in  the  same  animal  so 
long  as  it  remains  in  a  natural  state;  the  second  is  the  investi- 
gation of  the  variations  due  to  the  heart's  action,  to  respira- 
tion, or  to  arterial  contractility,  respectively. 

For  the  determination  of  the  mean  arterial  pressure,  and  of 
those  variations  which  belong  to  the  secontl  and  third  class, 
preference  is  to  be  given  to  the  ordinary  mercurial  manometer, 
one  branch  of  which  is  connected  with  the  artery  to  be  investi- 
gated, while  the  other  is  open.  This  instrument,  as  so  applied, 
constitutes  what  Poiseuille  designated  by  the  term  hsemadyna- 
mometer.  It  was  employed  in  this  simple  form  until  Ludwig, 
in  1848,  by  his  invention  of  the  kymograph,  laid  the  foundation 
of  the  more  exact  methods  of  investigating  blood-pressure 
which  are  now  in  use.  Just  as  the  first  method  of  Poiseuille 
originated  in  the  ruder  experiments  of  our  countryman  Hales, 


BY    DR.    BURDON-SANDERSON.  219 

so  the  notion  of  the  kymograph  is  said  to  have  been  suggested 
by  a  contrivance  of  Watt's  for  registering  the  pressure  of  the 
steam-engine. 

The  principle  of  the  kymograph  consists  in  causing  a  pen, 
fixed  horizontally  at  the  upper  end  of  a  vertical  rod,  the  lower 
end  of  which  rests  by  a  floating  piston  on  the  surface  of  the 
mercurial  column  in  the  distal  open  limb  of  the  manometer,  to 
write  the  up  and  down  movements  of  the  column  on  a  surface 
of  paper  progressing  horizontally  at  a  uniform  rate  by  clock- 
work. Since  the  time  that  Ludwig  first  employed  it,  the  con- 
trivance has  developed  into  a  method  now  commonly  known  as 
the  graphic  method. 

Description  of  the  Kymograph  and  Accessory  Ap- 
paratus now  used  in  the  Laboratory  of  University 
College.1 — 1.  The  arterial  canula  is  a  T-shaped  tube  of  glass, 
of  the  size  and  form  shown  in  fig.  193,  c.  By  its  stem  it  is  con- 
nected with  the  manometer;  one  branch  is  drawn  out  and 
bevelled,  the  other  is  of  the  same  size  as  the  stem,  and  when  in 
use  is  fitted  with  a  short  bit  of  caoutchouc  tubing,  guarded  by 
a  steel  clip. 

The  canulated  end  is  made  as  follows:  The  tube  which  it  is 
intended  to  use  for  the  purpose  is  first  softened  in  the  flame  of 
the  gas  blow-pipe,  and  drawn  out  gently  at  the  softened  part. 
It  is  then  allowed  to  cool,  and  again  heated  in  a  pointed  flame 
at  x,  and  drawn  out  so  as  to  make  it  assume  the  form  193,  b. 
It  is  then  scratched  with  a  sharp  three-cornered  file  opposite 
x,  and  sundered  by  drawing  the  one  end  of  the  tube  from  the 
other  in  the  direction  of  its  axis.  The  last  step  in  the  process 
consists  in  filing  off  the  cut  end  in  the  direction  of  the  dotted 
line,  and  smoothing  the  edges  b}r  touching  them  with  the 
border  of  an  ordinary  gas  flame.  A  tube  of  this  kind  can  be 
inserted  with  great  ease  into  an  artery  of  considerably  less 
diameter  than  itself.  Canulae  of  glass  are  always  to  be  pre- 
ferred to  those  of  silver,  not  merely  on  the  ground  of  facility 
of  introduction,  but  because  a  glass  surface  is  much  less  apt 
than  one  of  metal  to  determine  coagulation  of  the  blood  which 
comes  into  contact  with  it. 

2.  The  stem  of  the  arterial  canula  communicates  with  the 
proximal  arm  of  the  manometer  (see  fig.  202)  by  a  tube  (c),  of 
which  the  part  next  the  canula  only  is  of  India-rubber.  The 
rest  is  of  lead;  the  purpose  of  the  arrangement  being  to  avoid 
a  certain  modification  of  effect  due  to  the  yielding  of  the  wall 
of  the  tube,  which  becomes  appreciable  if  the  whole  connector 
is  elastic. 

1  This  instrument  was  made  for  me  by  Mr.  Ilawksley,  of  Blenheim 
Street,  and  has  advantages  over  any  other  form  with  which  I  am 
acquainted. 


220  CIRCULATION   OF    THE    BLOOD. 

3.  The  proximal  arm  of  the  manometer  communicates  at  its 
end,  by  means  of  along  flexible  tube  (b)  guarded  by  a  clip,  with 
a  "  pressure  bottle"  containing  solution  of  bicarbonate  of  soda. 
A  horizontal  arm,  which  springs  from  it  near  the  top,  is  con- 
tinuous with  the  lead  tube  already  mentioned. 

4.  The  manometer  is  fixed  to  the  edge  of  the  small  mahogany 
table  on  which  the  recording  apparatus  stands  by  means  of 
a  brass  clamp,  which  admits  of  its  being  raised  or  lowered  at 
will.  The  floating  piston  and  rod  (a)  are  made  of  black  vul- 
canite. The  piston  is  in  the  form  of  an  inverted  cup,  which 
embraces  the  convex  surface  of  the  mercurial  column.  The 
rod  is  quadrangular,  and  works  in  a  guide,  fixed  at  a  height  of 
six  inches  above  the  upper  end  of  the  tube,  b}r  which  it  is  kept 
vertical.  The  writer,  a  fine  sable  miniature  pencil,  is  supported 
on  the  rod  by  a  horizontal  arm  of  thin  wire,  one-third  of  an  inch 
in  length.  One  end  of  the  wire  is  coiled  round  the  rod,  the 
other  round  the  stem  of  the  pencil.  From  the  guide  just  men- 
tioned springs  a  horizontal  arm,  from  which  a  silk  plummet-line 
is  allowed  to  fall  in  such  a  way  that  it  rests  against  the  hori- 
zontal part  of  the  wire.  By  this  means  the  point  of  the  writer 
is  kept  in  constant  contact  with  the  paper,  without  exercising 
too  much  pressure. 

G.  The  recording  apparatus  consists  of  a  single  cylinder, 
which  revolves  at  a  constant  rate  of  one  revolution  per  minute. 
The  clock-work  by  which  it  is  moved  is  constructed  b}'  Mr. 
Hawksley  on  the  model  of  the  so-called  "  Foucault's  Regula- 
tor." To  the  right  of  the  cylinder,  as  seen  in  the  drawing,  is 
shown  a  large  brass  bobbin,  of  the  same  width  as  the  cylinder, 
on  which  a  riband  of  paper  is  tightly  rolled  b^y  machineiy,  of 
sufficient  length  to  serve  for  many  hundred  observations. 
From  the  bobbin  the  paper  riband  is  drawn  off  by  the  cylinder 
as  it  revolves,  against  the  surface  of  which  it  is  accurately 
applied,  furnished  with  ivory  friction  wheels. 

34.  Rules  and  Precautions  to  be  observed  in  mak- 
ing a  Kymographic  Observation. — Before  commencing, 
it  is  necessaiy  to  see  that  the  manometer  is  in  proper  order. 
The  mercury  in  the  distal  column  must  be  clean  and  dry,  and 
the  writing  pencil  moist  and  free  from  the  remains  of  the  ink. 
To  insure  this,  it  should  always  be  steeped  in  water  after  each 
observation. 

To  dry  mercury,  the  best  Swedish  filtering  paper  is  used. 
It  is  cleaned  by  straining  it  through  calico,  or  still  better 
through  chamois  leather.  If  the  latter  is  used,  it  must  be 
strained  under  a  considerable  pressure.  The  system  of  tubes 
communicating  with  the  proximal  limb  of  the  manometer 
must  now  be  filled  with  solution  of  bicarbonate  of  soda.  To 
accomplish  this,  the  arterial  tube  is  first  closed  by  a  clip,  and 
the  solution  introduced  with  the  aid  of  a  pipette  into  the  open 


BY    DR.    BURDON-SANDERSON.  221 

end  of  the  proximal  limb.  Some  of  the  solution  is  then 
allowed  to  flow  from  the  bottle  by  the  long  communicating 
tube  (b)  so  as  to  fill  it  completely,  after  which  its  end  is 
brought  into  communication  with  the  manometer.  If  any  air 
bubbles  are  introduced,  they  are  readily  got  rid  of  through 
the  artery  tube.  According  to  the  height  to  which  the  press- 
ure bottle  is  raised  above  the  level  of  the  manometer,  the 
mercurial  column  in  the  distal  limb  rises  above  that  in  the 
proximal.  It  must  be  adjusted  so  that  the  difference  between 
the  two  is  a  little  less  than  the  probable  arterial  pressure  of 
the  animal  to  be  used.  This  having  been  accomplished,  and 
the  communication  between  the  manometer  and  the  pressure 
bottle  closed,  all  is  ready. 

The  only  arteries  which  are  used  for  observations  of  arterial 
pressure  are  the  carotid  and  the  crural.  On  the  whole,  the 
latter  is  preferable  ;  for  the  carotid  cannot  be  exposed  without 
some  risk  of  disturbing  the  vagus  nerve.  In  the  rabbit,  the 
carotid  is  prepared  as  follows :  The  animal  having  been 
secured  on  Czermak's  rabbit-board,  and  the  fur  clipped,  the 
skin  is  pinched  up  between  the  finger  and  thumb  on  either 
side  of  the  upper  end  of  the  trachea,  so  as  to  form  a  horizontal 
fold,  which  an  assistant  divides  vertically.  As  soon  as  any 
slight  bleeding  has  ceased,  the  wound  is  dabbed  with  a  sponge 
moistened  with  saline  solution,  and  the  fascia,  which  stretches 
from  the  edge  of  the  sterno-mastoid  to  the  middle  line,  is 
seized  with  blunt  forceps  and  opened  with  knife  or  scissors. 
The  opening  having  been  enlarged  with  the  aid  of  a  second 
pair  of  blunt  forceps,  the  sterno-mastoid  is  slightly  drawn 
aside,  so  as  to  bring  the  artery,  with  its  three  accompanying 
nerves,  the  vagus,  the  depressor,  and  the  sympathetic,  into 
view.  The  sheath  having  been  opened,  the  artery  is  raised  on 
a  blunt  hook,  and  easily  cleared  from  its  attachments  to  a 
distance  of  three-quarters  of  an  inch  in  either  direction.  The 
distal  end  of  the  prepared  part  is  tied,  and  the  proximal  end 
closed  by  a  clip.  A  splinter  of  wood,  or  a  bit  of  card  of 
similar  shape,  is  slipped  under  the  artery  close  to  the  ligature, 
and  a  second  ligature  looped  round  it.  Finally  a  V-shaped 
snip  is  made  in  its  wall  with  scissors  which  cut  well  at  the 
point ;  the  canula  is  inserted,  and  the  ligature  tightened  round 
the  constriction.  The  whole  operation  ought  to  be  accom- 
plished in  three  minutes  ;  it  is  desirable  to  have  an  assistant. 
The  instruments  required  are  indicated  by  the  italics.  (See 
fig.  203.)  They  must  be  placed  in  readiness  on  the  table  of 
the  kymograph.  Czermak's  rabbit  supporter  is  shown  in  fig. 
204.  It  consists  of  a  strong  wooden  board,  about  8  inches 
wide  and  30  inches  long.  At  one  end  it  is  strengthened  with 
an  iron  plate,  into  which  a  strong  vertical  stem  is  screwed. 
This  stem  bears  a  sliding  block  of  brass,  in  which  an  iron  rod 


222  CIRCULATION    OF    THE    BLOOD. 

also  slides  horizontally.  Near  its  base  it  is  bent  twice  at 
right  angles,  so  that  the  upper  part  on  which  the  block  slides 
is  not  in  the  same  line  with  the  lower  part.  Consequently  the 
rod,  while  still  remaining  horizontal,  can  be  moved  in  four 
different  ways.  It  can  be  shortened  or  lengthened,  heightened 
or  lowered,  rotated  round  its  own  axis,  rotated  round  the  axis 
of  the  stem,  or  moved  from  side  to  side  without  change  of 
direction.  It  ends  in  a  kind  of  forceps  the  blades  of  which, 
when  kept  closed  by  the  adjusting  screw,  seize  upon  the  head 
of  a  cat  or  rabbit  in  such  a  manner  as  to  hold  it  firmly  without 
inflicting  the  slightest  injury.  The  neck  of  the  animal  rests 
on  a  cylindrical  cushion,  covered  with  water-proof  cloth,  and 
the  rest  of  the  body  on  a  mattress  of  similar  material.  Along 
the  edges  of  the  board  there  are  convenient  attachments  for 
the  extremities. 

The  preparation  of  the  crural  artery  is  even  more  simple  than 
that  of  the  carotid.  The  skin  having  been  divided  in  a  line 
leading  from  the  middle  of  Poupart's  ligament  towards  the  inner 
side  of  the  knee  by  first  pinching  up  a  fold  of  skin  as  above 
directed,  the  pulsation  of  the  artery  is  felt  by  the  finger  in  the 
hollow  between  the  adductor  muscles  and  those  which  cover  the 
femur.  The  sheath  of  the  vessels  having  been  exposed  from 
Poupart's  ligament  downwards,  the  vein  and  crural  nerve  are 
seen,  the  artery  lying  behind  and  to  the  outer  side  of  the  former. 
On  drawing  the  vein  inwards  it  is  easily  got  at,  and  must  he 
prepared  from  the  origin  of  the  arteria  j)rofunda  close  to  Pou- 
part's ligament,  nearly  to  the  point  at  which  it  enters  the  ad- 
ductor ;  first  giving  off  the  arteria  saplwna,  which  accompanies 
the  saphenous  nerve  and  veins.  The  lower  of  the  two  circum- 
flex arteries  which  are  given  off  within  a  short  distance  from 
the  profunda  must  be  tied  doubly  and  divided  hetween  the  liga- 
tures, as  it  is  desirable  to  place  the  clip  as  high  as  possible. 
In  the  dog  or  cat,  the  operation  is  equally  simple,  but  requires 
more  time  on  account  of  the  greater  abundance  of  fat  in  these 
animals. 

The  canula  having  been  inserted,  the  next  step  is  to  bring 
the  artery  into  communication  with  the  manometer.  The  clip 
on  the  artery  remaining  closed,  that  on  the  stem  of  the  canula 
is  opened  for  a  couple  of  seconds.  At  once  the  soda  solution 
fills  the  canula  and  passes  out  bj'  its  open  branch.  In  doing 
this,  great  care  must  be  taken  not  to  allow  the  solution  to  flow 
into  the  wound.  Air  bubbles,  if  they  exist,  are  got  rid  of  by 
passing  a  thin  rod  of  whalebone  into  the  canula,  which  must 
then  be  closed  by  means  of  the  terminal  clip.  All  being  now 
ready,  the  stem  of  the  canula  is  finally  opened,  and  the  clip  re- 
moved from  the  artery.  The  mercurial  column  at  once  begins 
to  oscillate ;  but  no  record  should  lie  taken  until  a  minute  or 
two  have  elapsed,  for  it  often  happens  that  a  small  quantity  of 


BY    DR.    BURDON-S  ANDERSON.  223 

soda  solution  enters  the  artery  and  produces  a  slight  and  transi- 
tory disturbance  of  the  circulation.  If,  indeed,  the  previously 
existing  pressure  in  the  artery  tube  is  somewhat  less  than  that 
of  the  artery,  no  such  effect  occurs;  but  inasmuch  as  we  have 
no  means  of  knowing  the  arterial  pressure  of  any  particular 
animal  beforehand,  it  is  usually  unavoidable. 

A  kj-mographic  observation  may  last  a  few  minutes  or  several 
hours,  according  to  the  question  to  be  investigated.  In  the 
latter  case,  tracings  are  taken  at  intervals.  Two  persons  are 
required,  one  of  whom  performs  the  experiment,  while  the  other 
undertakes  the  charge  of  the  writing  apparatus,  and  notes  on 
the  paper-roll,  with  a  soft  pencil,  the  events  as  they  occur  and 
the  times  of  beginning  each  tracing.  In  this  wa}-  the  roll 
stands  in  the  place  of  a  protocol,  and  is  less  liable  to  errors  of 
'time  and  order  than  any  other  kind  of  record. 

35.  Measurement  of  absolute  Arterial  Pressure  at 
any  given  moment  during  the  period  of  observation. 
— For  this  purpose  it  is  necessary  to  draw  the  abscissa  of  the 
pi*essure  curve,  i.  e.,  the  horizontal  line  which  the  writer  would 
have  drawn  had  the  arterial  pressure  been  equal  to  that  of  the 
atmosphere.  This  is  accomplished  immediately  after  the  ter- 
mination of  the  experiment,  by  closing  the  stem  of  the  canula 
and  then  removing  it  from  the  artery,  and  immersing  it  iu  a 
capsule  containing  soda  solution,  standing  at  a  level  equal  to 
that  of  the  artery.  The  clip  having  been  opened,  the  clock- 
work is  set  in  motion  for  a  moment,  and  a  horizontal  line  drawn 
which  coincides  with  the  abscissa  required.  In  this  line  the 
paper  is  then  pierced  with  a  pointed  instrument  in  such  a  wa}r 
as  to  perforate  the  several  layers  of  paper  at  the  same  level. 
By  removing  the  roll  from  the  cylinder  and  connecting  the 
holes,  a  horizontal  straight  line  is  obtained  which  runs  from 
end  to  end  of  the  record.  By  drawing  an  ordinate  from  any 
point  in  the  tracing  to  this  line,  measuring  its  length  in  milli- 
metres and  doubling  the  result,  the  absolute  arterial  pressure 
at  the  corresponding  moment  is  obtained  in  millimetres  of 
mercury. 

The  mean  arterial  pressure  is  obtained  by  drawing  ordi- 
nates  at  regular  intervals  and  measuring  the  length  of  each. 
The  mean  of  the  lengths  corresponding  to  the  period  investi- 
gated, multiplied  by  two,  is  the  mean  pressure  required.  [I 
never  use  paper  divided  into  squares — in  other  words,  with  the 
ordinates  ready  measured — finding  by  experience  that  they  do 
not  tend  to  accuracy.  Moreover,  such  paper  is  expensive,  and 
thereby  furnishes  an  inducement  for  an  undesirable  economy 
in  its  use.]  In  all  normal  kymographic  records  it  is  seen  that 
the  arterial  expansions  due  to  the  contractions  of  the  left  ven- 
tricle are  indicated  by  oscillations  which  differ  very  materially 
in  form,  and  that  these  differences  are  dependent  on  their  fre- 


224  CIRCULATION   OF    THE    BLOOD. 

qucncj\  (See  Fig.  206.)  When  extreme]}-  frequent,  they  are 
mere  undulations;  but  when  the  intervals  are  longer,  they  ex- 
hibit forms  which,  as  we  shall  afterwards  see,  have  a  definite 
relation  to  the  changes  of  tension  which  actually  occur  in  the 
arteries  during  each  cardiac  period.  It  is  further  seen  that 
there  are  larger  waves  which  correspond,  not  to  the  beats  of  the 
heart,  but  to  the  respiration — the  valley  and  ascending  limb 
of  each  of  these  greater  undulations  corresponding  to  inspira- 
tion, the  summit  and  descending  limb  to  expiration  and  to  the 
pause.  These  and  other  details  will  be  referred  to  in  future 
sections. 

Section  II. — Observation  op  the  successive  Changes  of  Arte- 
rial Tension  wnicn  occur  during  each  Cardiac  Period. 

In  studying  tracings  obtained  by  the  mercurial  kymograph, 
it  is  to  be  borne  in  mind  that  what  is  inscribed  on  the  cylinder 
is  not  the  record  of  the  actual  movement  of  the  artery,  but  of 
the  oscillations  of  the  mercurial  column.  It  is  true  that  the 
latter  are  the  immediate  results  of  the  former,  and  that  the 
elevation  of  the  distal  column  produced  by  each  arterial  ex- 
pansion has  some  relation  to  the  increase  of  lateral  pressure, 
of  which  the  expansion  is  the  expression  ;  but  the  curve  drawn 
is  not  that#of  the  arteiy,  but  of  the  manometer.  The  artery 
expands  suddenty,  the  mercury  rises  comparatively  slowly,  so 
that  at  the  moment  it  attains  its  acme  the  artery  has  already 
collapsed.  Consequently,  if  the  interval  between  each  pulsa- 
tion and  its  successor  is  very  short,  the  extent  of  oscillation 
(or,  as  it  is  usually  called,  the  excursion)  of  the  manometer 
is  relatively  too  small  ;  and  converse^*,  if  the  interval  is  much 
prolonged,  the  excursion  is  relatively  too  great.  The  descent 
of  the  column  is  almost  entirely  independent  of  the  collapse 
of  the  artery.  It  falls  back  to  equilibrium,  and  describes  a 
curve,  which  (as  may  be  learnt  by  comparison)  has  the  same 
characters  as  that  made  by  the  lever  in  returning  to  its  origi- 
nal position,  by  whatever  wa}T — as,  e.  g.,  by  squeezing  the  con- 
necting-tube— the  equilibrium  of  the  manometer  may  have  been 
momentarily  disturbed. 

This  being  the  case,  it  is  eas}'  to  understand  that  no  conclu- 
sion can  be  derived  from  observations  with  the  mercurial  mano- 
meter, either  as  to  the  duration  of  the  effect  produced  by  each 
contraction  of  the  heart,  or  as  to  the  relative  duration  of  the 
periods  of  expansion  and  collapse.  The  use  of  the  instru- 
ment is  limited  to  the  investigation  of  the  mean  pressure,  and 
of  those  varieties  of  pressure  of  which  the  periods  of  recur- 
rence are  long  enough  to  prevent  their  being  interfered  with 
by  the  proper  oscillations  of  the  instrument. 


BY    DR.    BURDOX-SANDERSOX.  225 

36.  The  Spring  Kymograph. — If  we  desire  to  obtain  a 
record  of  the  complicated  succession  of  variations  of  arterial 
pressure  which  constitute  an  act  of  pulsation,  precisely  as 
they  occur  as  regards  order,  duration,  and  degree,  or  of  the 
exact  interval  of  time  between  the  close  of  one  arterial  expan- 
sion and  the  commencement  of  the  next,  the  instrument  with 
which  we  write  must  be  of  such  a  nature  that  it  shall  transmit 
the  movements  communicated  to  it  without  mixing  with  them 
any  movements  of  its  own.  The  most  perfect  of  such  instru- 
ments is  the  so-called  Federkymographion  of  Professor  Fick. 
The  construction  of  the  instrument  will  be  readily  understood 
with  the  aid  of  Fig.  205.  It  consists  essentially  of  a  C-shaped 
hollow  spring  of  thin  metal.  The  cavity  of  the  spring  is  filled 
with  spirits  of  wine,  and  communicates  with  the  arteiy  by  means 
of  a  connecting-tube  containing  bicarbonate  of  soda.  As  the 
pressure  increases,  the  crescentic  spring  tends  to  straighten, 
and  vice  versa.  Hence,  if  the  proximal  end  is  fixed,  the  distal 
end  performs  movements  which  follow  exactly  the  variations 
of  arterial  tension.  These  movements  are  of  very  small  ex- 
tent, but  they  are  so  exact  that  the  slightest  and  most  transi- 
tory variations  are  expressed  by  them.  Before  they  are  writ- 
ten on  the  cylinder  they  must  be  enlarged  by  a  lever. 

It  is  not  necessary  to  make  any  remarks  as  to  the  mode  of 
connecting  the  spring  kymograph  with  an  artery,  the  modus 
operandi  being  the  same  as  that  described  in  §  34.  It  is,  how- 
ever, to  be  noted,  that  if  it  is  intended  to  use  the  tracing  ob- 
tained by  it  for  the  purpose  of  determining  the  absolute  arte- 
rial pressure,  the  instrument  must  be  first  graduated  by  com- 
parison with  a  mercurial  manometer.  This  is  effected  as 
follows :  The  kymograph  being  placed  so  as  to  write  on  the 
recording  cylinder,  its  artery  tube,  which  communicates  by  a 
side  opening  with  a  pressure  bottle,  is  united  with  the  proxi- 
mal arm  of  the  manometer.  The  pressure  bottle  is  first 
lowered  until  the  liquid  it  contains  stands  at  the  same  level 
as  the  mercuiy  in  the  proximal  arm.  A  tracing  is  made  on 
the  cylinder,  which  is  the  abscissa.  The  bottle  is  then  raised 
till  the  distal  mercurial  column  is  ten  millimetres  higher  than 
the  proximal,  and  a  second  tracing  taken,  and  so  on  at  suc- 
cessive increments  of  10  mill,  pressure,  up  to  150  mill,  or 
more.  LJy  measuring  vertically  the  distances  in  millimetres 
between  the  horizontal  lines  so  traced  and  the  abscissa,  a 
series  of  results  are  obtained  which  express  the  values  of  the 
ordinates  of  the  tracing  in  millimetres  of  mercurial  pressure. 

In  tracings  obtained  by  the  spring  kymograph  it  is  seen 
that  the  ascent  of  the  lever,  which  corresponds  to  the  period 
during  which  the  artery  is  acted  on  by  the  contracting  ven- 
tricle, is  abrupt — indeed,  nearly  vertical  ;  that  towards  the 
vertex  the  tracing  changes  direction,  gradually  approaching 
15 


22«3  CIRCULATION    OF    THE    BLOOD. 

a  horizontal  line  touching  it  at  the  highest  point;  that  the 
line  of  descent — much  more  oblique  than  that  of  ascent — ter- 
minates in  the  same  way  by  gradually  approaching  a  horizon- 
tal line  touching  the  curve  at  its  lowest  point.     (See  fig.  207.) 

37.  Observation  of  the  Expansive  Movements 
■which  accompany  the  successive  Changes  of  Arte- 
rial Pressure  above  described. — When  an  artery  is  ex- 
posed in  a  living  animal,  as,  e.  ;/.,  when  it  is  prepared  in  the 
manner  described  in  §  34,  two  kinds  of  motion  are  seen.  The 
bit  of  artery  which  is  separated  from  the  surrounding  parts 
lengthens,  and  its  diameter  visibly  increases  each  time  it  is 
acted  on  by  the  contracting  heart.  Of  these  two  phenomena, 
the  first  is  commonly  called  locomotion,  because  in  certain 
superficial  arteries  of  the  human  bod}-  (especially  when  1 1 1 c- v 
are  enlarged  in  advanced  life),  the  artery,  as  it  lengthens,  is 
compelled  to  bend  to  one  side  or  the  other,  and  thereby 
visibly  changes  its  place  each  time  that  it  is  distended.  The 
other,  viz.,  the  expansive  movement,  is  called  pulsation,  and 
is  practically  of  great  importance,  seeing  that  it  is  the  only 
phenomenon  of  the  arterial  circulation  which  admits  of  being 
investigated  without  exposing  the  artery,  and  consequent!}7 
affords  the  only  direct  means  by  which  we  can  judge  of  its 
ever-varying  conditions  in  man. 

Arteries  being  elastic,  their  changes  of  diameter  express  all 
changes  of  the  pressure  exercised  by  their  liquid  inelastic  con- 
tents on  their  internal  surfaces.  J  f.  therefore,  the  expansive 
movements  of  an  exposed  artery  were  to  be  measured  and  re- 
corded graphical^7,  the  record  would  correspond  closely  with 
that  of  the  pressure  obtained  by  Fick's  k3Tmograph.  For  just 
as  in  that  instrument  the  variations  of  pressure  are  converted 
by  the  C-shaped  spring  into  nearl}'  rectilinear  movements,  the 
artery  expands  with  every  increase  of  pressure  on  its  internal 
surface,  and  contracts  with  eveiy  diminution  of  it,  so  that  any 
point  taken  on  its  surface  is  constantly  performing,  in  relation 
to  its  axis,  orderly  successions  of  rectilinear  movements  in 
opposite  directions. 

In  both  cases — that  of  the  spring  and  that  of  the  arteiy — 
the  expansion,  and  the  pressure  which  produces  it,  vary  in 
the  same  directions  during  the  same  times,  but  not  in  the  same 
degree.  As  regards  the  spring,  we  can  readily  determine  the 
relation  of  expansion  to  pressure  by  the  method  of  graduation 
described  in  the  preceding  paragraph,  and  so  use  the  former 
as  an  expression  for  the  latter.  In  the  case  of  the  artery,  no 
such  empirical  graduation  is  possible.  The  expansion  of  an 
artery,  or  any  other  elastic  tube,  due  to  any  given  increase  of 
pressure  against  its  internal  surface,  depends  upon  the  degree 
in  which  the  tube  is  already  distended  at  the  commencement 
of  the  act  of  expansion.     The  greater  the  original  distension, 


BY   DR.    BURDON-SANDERSON.  227 

the  less  will  be  the  effect ;  so  that  the  condition  of  an  artery 
in  which  the  expansive  movement  is  relatively  greatest,  is  that 
in  which  its  walls,  when  the  expanding  agency  is  suspended, 
are  in  the  state  of  elastic  equilibrium,  i.  e.,  when  the  minimum 
pressure  is  least.  A  moment's  consideration  teaches  us  that 
there  are  two  circumstances  which  must  diminish  the  minimum 
pressure  in  the  arteries,  viz.,  diminution  of  the  mean  arterial 
pressure,  and  prolongation  of  the  period  which  intervenes  be- 
tween one  expansive  act  and  its  successor.  In  other  words, 
the  less  frequent  the  contractions  of  the  heart  and  the  lower  the 
arterial  pressure,  the  greater  the  expansion  in  proportion  to 
the  expanding  force  which  produces  it. 

38.  The  Sphygmograph. — In  man,  no  artery  can  be  di- 
rectly measured  either  as  regards  pressure  or  expansion.  In 
feeling  the  pulse,  we  attempt  to  measure  both  by  the  sense  of 
touch,  and  obtain  results,  which,  although  incapable  of  nu- 
merical expression,  are  sufficiently  exact  to  be  of  great  value. 
In  the  sph\-gmograph,  an  attempt  has  been  made  to  obtain  the 
same  kind  of  information  by  a  mechanical  contrivance,  which 
the  physician  obtains  by  the  tactus  eruditus  ;  the  supposed 
advantage  of  the  instrumental  results  over  the  others  being, 
that  they  can  be  estimated  by  measurement  and  weighing,  and 
that  they  are  unaffected  by  variation  in  the  skill  and  tactile 
sensibility  of  the  observer. 

The  purpose  of  the  sphygmograph  is  to  measure  the  com- 
plicated succession  of  alternate  enlargements  and  diminutions 
which  an  artery  undergoes  whenever  blood  is  forced  into  it 
b}r  the  contracting  heart,  to  magnify  those  movements,  and  to 
write  them  on  a  surface,  progressing  at  a  uniform  rate  by 
watch-work. 

The  construction  of  the  instrument  is  so  well  known,  that 
it  is  scarcely  necessary  to  give  a  detailed  description  of  it.  It 
consists  essentially  of  three  parts:  a  frame  of  brass  which  is 
applied  along  the  outer  edge  of  the  volar  aspect  of  the  fore- 
arm, in  such  a  way  that  it  is  maintained  in  a  fixed  position 
with  reference  to  the  bones  of  the  wrist  and  radius — a  steel 
spring  which,  when  the  instrument  is  in  use,  presses  upon  the 
radial  artery  and  receives  its  movements — and  lastly,  mechani- 
cal arrangements  for  magnifying  these  movements  and  record- 
ing them.  Both  of  these  ends  are  accomplished  by  means  of  a 
light  wooden  lever  (a  a',  fig.  208)  of  the  third  order,  which  is 
supported  by  steel  points  (c).  There  is  a  second  lever  of  the 
same  order  (b  b)  which  has  its  centre  of  movement  near  the 
attachment  of  the  spring  (at  E).  It  terminates  in  a  vertical 
knife-edge  (n),and  is  traversed  by  a  vertical  screw  (t).  When 
the  extremity  of  the  screw  (\)  rests  upon  the  spring  above  the 
ivory  plate,  every  movement  of  the  plate  is  transmitted  to  this 
lever  (b  e),  and,  by  means  of  the  knife  edge,  to  the  wooden 


228  CIRCULATION    OF   THE    BLOOD. 

lever  (a  a').  The  purpose  of  the  screw  (t)  is  to  vary  at  will 
the  distance  between  the  wooden  lever  and  the  upper  surface 
of  the  spring,  without  interfering  with  the  mechanism  by  which 
the  movement  is  transmitted.  As  the  distance  between  the 
steel  points  (c)  and  the  knife-edge  (d)  is  much  less  than  the 
length  of  the  lever,  the  oscillations  of  the  extremity  of  the 
lever  (a7)  are  much  more  extensive  than  the  vertical  move- 
ments of  the  spring.  The  lever  ends  in  a  metal  point,  which 
writes  on  a  glass  plate  blackened  by  passing  it  rapidly  back- 
ward and  forward  through  the  flame  of  a  spirit-lamp  trimmed 
with  paraffin. 

When  this  instrument  is  applied  in  the  proper  manner  to 
the  wrist,  the  radial  artery  is  compressed  between  the  surface 
of  the  radius  and  a  spring,  the  bearing  of  which  is  in  a  fixed 
position  in  relation  to  that  surface.  This  being  the  case,  the 
spring  performs  movements  which  are  more  or  less  conform- 
able with  the  variations  of  the  diameter  of  the  artery.  These 
movements  are  transferred  in  a  magnified,  but  otherwise  little 
altered,  form  to  the  lever.  As  regards  the  relative  and  actual 
duration  of  the  movements,  the  correspondence  is  exact;  but 
as  regards  their  extent,  this  is  true  only  in  so  far  as  the  lever 
follows  the  movements  of  the  spring  with  precision,1  and  as 
the  strength  of  the  spring,  i.e..,  the  pressure  exercised  by  it  on 
the  artery,  is  adapted  to  the  antagonistic  pressure  exerted  by 
the  blood  stream  on  the  internal  surface,  and  to  the  extent  of 
the  movements  it  is  intended  to  measure. 

The  relation  between  the  pressure  of  the  spring  and  its  effect 
on  the  artery  is  a  complex  one,  and  need  only  be  considered 
here  in  so  far  as  is  necessary  for  the  interpretation  of  sphyg- 
mographic  results.  To  facilitate  our  understanding  of  it,  let 
us  call  the  position  which  the  spring  takes  when  left  to  itself 
its  equilibrium  position ;  and  as  regards  the  artery,  let  us  de- 
signate a  plane  parallel  to  the  surface  of  the  skin,  and  touch- 
ing the  surface  of  the  artery,  when  most  dilated,  the  plane  of 
expansion;  and  a  plane  in  similar  relation  to  it,  when  least 
expanded,  the  plane  of  collapse ;  and  to  simplify  the  problem, 
let  us  suppose  that  the  artery  is  not  covered  by  skin.  It  is 
evident  that,  if  the  sphygmograph  accomplished  its  professed 
end  completeby,  the  under  surface  of  its  spring  would  coincide 
with  one  of  these  planes  at  the  moment  of  the  pulse,  and  with 
the  other  during  the  interval.  The  question  is,  How  ought 
the  spring  to  be  set,  in  order  to  obtain  a  movement  which  shall 
approach  this  standard  of  perfection  as  nearly  as  possible  ? 
We  may  proceed  one  step  towards  answering  this  question 
without  difficulty.  It  should  be  set  so  that  if  the  spring  were 
in  the  equilibrium  position  its  under  surface  would  lie  within 

1  See  note  on  p.  235. 


BY    DR.    BURDON-SANDERSON.  229 

the  plane  of  collapse — i.  e.,  nearer  the  axis  of  the  artery.  For 
if  it  were  further  from  the  artery  it  would  be  affected  by  the 
arterial  movement  only  during  its  period  of  expansion,  remain- 
ing the  rest  of  the  time  motionless.  If,  on  the  other  hand,  it 
were  much  nearer,  the  vessel  would  be  flattened  against  the 
bone  during  the  period  of  collapse,  so  that  in  this  case,  as  in 
the  other,  there  would  be  no  motion  (of  the  spring)  during 
diastole.  Hence  it  is  easy  to  understand  how  it  happens  that 
the  tracings  obtained  with  excessive  and  defective  pressure  are 
very  similar  to  each  other  in  their  general  characters.  Stating 
the  same  tiling  in  other  words,  we  arrive  at  the  general  rule 
that  the  spring  must  be  so  set  that  the  ivory  plate  on  its  under 
surface  is  at  such  a  distance  from  the  opposed  surface  of  bone 
that  the  artery  is  pressed  upon  at  all  degrees  of  expansion,  j-et 
not  so  strongly  pressed  upon  as  to  bring  its  wails  into  contact 
even  when  it  is  relaxed.  Within  these  limits,  the  variations 
of  form  of  the  tracing — in  other  words,  its  departure  from 
truth — are  very  inconsiderable ;  so  that  observations  made  on 
the  same  individual  at  different  times  yield  closely  correspond- 
ing forms.  As,  however,  the  results  obtained  by  strong  press- 
ure are  less  subject  to  accidental  error  than  those  obtained 
with  weaker  ones,  it  is  better  always  to  begin  with  a  pressure 
sufficient  to  flatten  the  artery,  and  then  to  weaken  the  spring 
until  the  effects  of  over-compression  disappear — i.e.,  until  it  is 
found  that  the  lever  continues  to  descend  until  the  very  end 
of  diastole. 

39.  Use  of  the  Sphygraograph  as  a  Means  of  Appre- 
ciating those  Changes  of  Mean  Arterial  Pressure 
which  occur  in  Disease. — We  have  already  seen  that  the 
sphygmograph  is  of  no  use  as  a  gauge  of  arterial  pressure.  It 
is  possible,  however,  by  the  comparison  of  observations  made 
at  successive  periods  on  the  same  individual,  to  determine 
whether  the  arterial  tension  has  changed,  and  in  what  direc- 
tion the  change  has  taken  place.  We  have  seen  that  if  the 
spring  is  so  strong  that  the  artery  is  either  partially  or  en- 
tirely flattened  against  the  radius,  the  fact  is  indicated  b}'  tire 
cessation  of  the  motion  of  the  lever.  The  strength  of  spring 
which  is  required  to  bring  about  this  result  varies  with  the 
pressure;  by  which  the  artery  is  distended  ;  so  that  if  in  any  in- 
dividual the  arterial  pressure  is  increased,  a  greater  tension  of 
the  spring  is  required  to  compress  it  than  was  required  before. 
With  Marey'a  sphygmograph,  as  imported,  it  is  not  possible 
for  the  observer  to  avail  himself  of  this  principle,  because  the 
instrument  is  not  graduated — i.e.,  there  is.no  means  by  which 
the  pressure  exerted  by  the  spring  at  any  moment  can  be  ascer- 
tained. I  have  therefore  modified  that  instrument  as  follows 
(see  Fig.  20'.».  a  :  The  brass  frame,  instead  of  being  bound  on 
to  the  arm  by  bandages,  rests  firmly  on  the  bones  of  the  wrist 


230  CIRCULATION    OF    THE    BLOOD. 

(particularly  the  scaphoid)  by  a  plate  of  brass,  the  under  sur- 
face of  which  is  covered  with  ebonite.  In  the  middle  of  the 
upper  surface  of  this  plate  is  a  socket  for  the  reception  of  the 
point  of  a  finely-cut  screw,  which  revolves  in  it  freely.  Above, 
the  screw  ends  in  a  milled  head  (y),  between  which  and  its 
point  it  passes,  first  loosely  through  a  guide,  which  is  of  the 
same  piece  with  the  brass  plate;  and,  secondly,  through  a  hole 
in  the  end  of  the  brass  frame  of  the  sphygmograph  (f),  in 
which  it  fits  closely.  This  being  the  construction,  it  is  scarcely 
necessary  to  explain  that,  by  turning  the  milled  head,  the  dis- 
tance between  the  ebonite  surface  and  the  frame  is  varied 
according  to  t lie  direction  of  revolution,  and  that  in  this  way 
the  pressure  on  the  arteiy  may  be  readily  modified  when.the 
instrument  is  in  use.  The  extent  of  the  modifications  thus 
produced,  however,  still  remains  undetermined,  for  they  vary 
according  to  the  form  of  the  limb  and  the  relative  position  of 
the  arm  and  forearm  at  the  time  of  observation.  To  measure 
them,  we  must  have  recourse  to  another  method  which  is  at 
once  simple  and  accurate.  It  is  obvious  that,  provided  that 
the  spring  is  firml}-  and  immovably  fixed  in  its  place,  the  press- 
ure which  it  makes  against  any  object  pushed  against  it  from 
below  is  determinable  by  the  force  which  is  exerted  in  pushing 
it.  If,  for  example,  I  turn  the  instrument  upside  down,  and 
place  a  weight  of  200  grammes  on  what  was  before  the  under 
surface,  now  the  upper  surface,  of  the  spring,  I  push  it  back 
some  fraction  of  an  inch  from  its  position  of  equilibrium;  I 
learn  that,  whenever  it  is  pushed  back  to  this  extent,  the  press- 
ure it  exerts  on  the  surface  opposed  to  it  is  that  of  200 
grammes'  weight.  Repeating  the  experiment  with  a  series  of 
other  weights,  I  can  in  a  similar  way  obtain  other  measure- 
ments of  distance  corresponding  to  them,  and  thus,  by  com- 
bining the  results,  accomplish  the  graduation  of  the  spring  in 
.such  a  way  that  the  pressure  made  by  it  can  be  alwaj's  known 
from  the  extent  of  its  deflexion.  The  most  convenient  wa}r  of 
determining  this  deflexion  is  either  to  measure  the  distance 
between  the  head  of  the  steel  screw,  the  point  of  which  rests 
on  the  upper  surface  of  the  spring,  and  the  surface  of  the  brass 
lever,  with  a  scale  (as  shown  in  Fig.  210);  or,  better  still,  to 
have  the  screw  itself  graduated.  In  either  case,  care  must  be 
taken  to  fix  the  writing  lever  in  the  proper  position — i.e.,  in  a 
direction  which  coincides  with  the  direction  of  movement  of 
the  writing  surface — before  making  the  measurements. 

40.  The  Artificial  Artery  or  Arterial  Schema. — The 
phenomena  of  arterial  pulsation  can  be  best  studied  in  a  well- 
constructed  schema  or  artificial  artery,  consisting  in  an  elastic 
tube  through  which  water  is  propelled  by  an  artificial  heart, 
i.  e.,  by  a  pump  of  such  construction  that  it  discharges  its 
contents    into   the    tube    in    a    manner    which    mechanically 


BY    DR.    BURDON-SANDERSON.  231 

resembles  that  in  which  the  heart  discharges  its  blood  into  the 
arteries.  Several  instruments  of  this  kind  have  been  con- 
trived, from  the  simple  schema  of  E.  H.  Weber,  to  the  com- 
plicated "  artificial  heart"  of  Marey. 

It  may  be  stated  generally  that  those  forms  of  schema  are 
most  instructive  which  are  of  the  simplest  construction  ;  and 
inasmuch  as  the  object  in  view  is  not  to  illustrate  but  to 
explain,  it  is  of  no  importance  whatever  that  the  schema 
should  have  any  outward  resemblance  to  the  organs  of  circu- 
lation for  which  it  stands.  What  is  essential  in  a  schema  is, 
that  as  regards  the  quantity  of  liquid  discharged  at  each 
stroke  of  the  pump,  the  period  occupied  in  the  discharge,  the 
distribution  in  time  of  the  pressure  exercised  on  the  mass  of 
liquid  expelled,  and  the  resistance  opposed  to  the  terminal 
outflow  of  liquid  from  the  elastic  tube,  the  representation 
should  resemble,  as  closely  as  possible,  the  thing  represented. 
To  the  student,  it  is  far  from  an  advantage  that  the  resem- 
blance should  extend  beyond  this  to  the  details  of  external 
form  and  arrangement;  for  his  attention  is  thereby  apt  to  be 
drawn  oft"  from  the  essential  conditions  of  the  act,  to  the 
accessory  peculiarities  of  the  machine  which  produces  it.  Two 
kinds  of  schema  may  be  usefully  employed  for  the  study  of 
the  phenomena  of  the  pulse,  which  differ  from  each  other  in 
the  construction  of  the  pump  which  does  the  work  of  the 
heart.  The  first  is  represented  in  fig.  211.  Here  the  pump 
consists  of  a  glass  tube  (a),  closed  at  the  upper  end,  and 
connected  below  by  two  branches — on  one  side  with  a  cistern, 
at  a  level  of  some  eight  or  ten  feet  above  the  table ;  on  the 
other,  with  the  experimental  tube  which  represents  the  artery. 
These  communications  are  controlled  by  valves,  placed  at  the 
opposite  ends  of  a  horizontal  lever  (e,  d)  of  such  construction 
that  the  same  act  which  closes  the  one  must  necessarily  open 
the  other ;  so  that,  as  regards  their  actions,  one  represents  the 
semilunar,  the  other  the  auriculo-ventricular  valves  of  the 
heart.  By  means  of  a  spring  (shown  in  the  figure  to  the  right 
of  d),  when  the  apparatus  is  not  working,  i.  e.,  during  the 
period  corresponding  to  diastole,  the  former  is  kept  closed, 
the  latter  open.  Under  these  circumstances,  the  water  rises 
in  the  tube,  compressing  the  column  of  air  which  it  contains 
in  a  proportion  which  is  determined  by  Marriotte's  law.  If, 
as  in  the  present  instance,  the  pressure  is  about  one-third  of 
an  atmosphere,  the  volume  of  the  inclosed  air  is  diminished  in 
the  proportion  of  2  :  3,  and  so  on.  When,  by  depressing  the 
opposite  end  of  the  lever,  the  aortic  valve  is  opened,  and  the 
mitral  closed,  the  compressed  air  suddenly  expands,  and  forces 
the  water  which  the  tube  contains  into  the  aorta.  We  shall 
see,  when  we  come  to  consider  the  modes  of  contraction  of 
the  heart,  that  the  above  is  as  close  an   imitation   as  could  be 


232  CIRCULATION    OF    THE    BLOOD. 

made  by  any  artificial  means.  Just  as,  when  the  heart  con- 
tracts, it  compresses  its  contents  most  energetically  at  the 
outset,  while  its  force  rapidly  diminishes  towards  the  end  of 
the  systole,  so  here  the  most  rapid  movement  of  the  column  is 
at  the  first  moment  after  the  depression  of  the  lever. 

The  arterial  tnhc  where  it  passes  under  the  valve  D  is  ahout 
four  lines  in  thickness.  Soon  it  divides  into  two  branches  of 
smaller  diameter,  each  of  which  is  several  yards  long.  One  of 
these  tubes  passes  under  the  spring  of  the  sphygmograph, 
which  is  fixed  at  ri  in  such  a  manner  that  tracings  may  be 
conveniently  taken.  Both  open  finally  into  a  waste  basin  ; 
but  each  is  provided  with  screw  clamps,  by  which  it  can  be 
compressed  or  constricted  at  any  desired  distance  from  the 
pump.  The  purpose  of  the  bifurcation  is,  that  the  observer 
may  be  enabled,  without  interfering  in  any  way  with  the  con- 
dition of  the  tube,  of  which  the  expansive  movements  are  re- 
corded sphygmographically,  to  vary  the  quantity  of  liquid 
which  is  discharged  through  it  per  minute.  To  experiment 
with  the  schema  satisfactorily,  it  is  desirable  to  leave  the 
working  of  the  lever  to  an  assistant,  or,  still  better,  to  arrange 
the  apparatus  so  that  the  work  can  be  done  by  an  electro- 
magnet. The  observer  is  then  at  liberty  to  watch  the  effect  of 
modifications  of  resistance,  etc.,  on  the  form  of  the  tracings 
while  they  are  in  progress.  The  most  important  facts  to  be 
demonstrated  with  the  aid  of  the  schema,  as  above  described, 
are  the  following: — 

1.  It  is  shown  that  the  artificial  and  the  natural  pulse  resemble 
each  other  closely,  each  consisting  in  a  succession  of  expansive 
and  contractile  movements  which  always  occur  in  the  same 
order  (.see  Fig.  212,  a).  In  describing  these  movements,  it  is 
convenient  to  speak  of  the  experimental  tube  as  the  artery,  and 
to  assume  that  elevation  of  the  lever  of  the  sphygmograph  is 
equivalent  to  expansion  of  the  tube,  and  depression  to  contrac- 
tion. This  granted,  the  tracing  shows  that  when  the  valve  D 
is  opened,  a  sudden  expansion  of  the  artery  takes  place;  that 
so  long  as  the  heart  continues  to  act  the  vessel  remains  full, 
and  that  the  cessation  of  the  injection  of  liquid  from  behind  de- 
termines a  contraction  of  the  artery  which  is  as  rapid  as  the 
previous  expansion.  Xo  sooner  has  the  artery  accomplished 
its  contraction  than  it  begins  a  second  expansion  inferior  to 
the  first  both  in  extent  and  rapidity ;  and  then  finally  contracts, 
continuing  to  get  smaller  until  the  aortic  valve  again  opens. 

2.  It  can  next  be  shown  that  just  as  the  expansion  of  the 
lever  is  consequent  on  the  opening  of  the  aortic  valve,  so  its 
descent  is  consequent  (not  on  the  closing  of  the  valve,  but)  on 
the  cessation  of  the  injection  of  liquid  by  the  pump,  i.  e.,  the 
cessation  of  the  systolic  contraction  of  the  ventricle.'  To  prove 
this,  I  use  a  contrivance  which  will  be  readily  understood  from 


BY    DR.    BUBDON-SANDERSON.  233 

the  figure.  Its  purpose  is  to  write  on  the  plate  of  the  sphyg- 
mograph  the  duration  of  the  injection  of  liquid.  It  consists  of 
a  cylinder  of  box-wood  (Fig.  211,  h),  the  steel  axis  of  which  rests 
horizontally  on  bearings  so  placed  that  the  cylinder  revolves  in  a 
direction  at  right  angles  to  that  of  the  movement  of  the  plate  at 
a  short  distance  from  it.  From  one  side  of  the  cylinder  a  steel 
needle  projects,  which,  when  the  cylinder  turns,  makes  a  mark 
on  the  smoked  surface.  Hound  one  side  of  the  cylinder  runs 
it  cord  of  spun  silk,  the  two  ends  of  which  stretch,  one  from 
either  side  of  it,  to  the  point  of  a  vertical  arm  (l)  ;  this  arm 
springs  from  the  wooden  lever  already  described,  by  which  the 
valves  are  opened  and  shut.  Of  the  two  cords,  the  upper  one 
is  rendered  partly  elastic  by  the  interposition  of  a  short  length 
of  caoutchouc.  So  long  as  the  aortic  valve  is  closed,  the  needle 
remains  in  contact,  but  the  moment  the  valve  is  opened,  it  is 
withdrawn,  and  we  obtain,  first,  an  upper  horizontal  line, broken 
at  regular  intervals — which  are,  of  course,  limited  in  time  by 
the  opening  and  closing  of  the  aortic  valve — and,  secondly, 
a  pulse-tracing  (Fig.  212,  6),  which  may  be  compared  with 
it.  This  exact  correspondence  between  the  length  of  time  the 
heart  is  acting  and  the  time  which  elapses  between  the  begin- 
ning of  the  expansion  and  the  commencement  of  the  contrac- 
tion, affords  evidence  that  the  latter  is  dependent  on  the 
former. 

3.  Lastl}*,  it  can  be  shown  that  the  second  expansion  is  not, 
as  might  be  supposed,  connected  with  the  closure  of  the  com- 
munication between  the  pump  and  the  elastic  tube  (the  shut- 
ting of  the  aortic  valve),  but  is  a  consequence  of  the  disturb- 
ance of  equilibrium  produced  in  the  tube  itself  by  the  act  of 
distension.  To  demonstrate  this,  the  second  expansion  must 
be  studied  under  various  conditions  and  by  various  methods; 
among  the  best  is  the  following:  A  narrow  tube,  closed  at  one 
end,  and  containing  air,  is  connected  by  means  of  a  T-piece 
with  the  experimental  tube  or  artery.  The  volume  of  air  con- 
tained in  the  tube  varies  with  the  pressure,  indicating  its  varia- 
tions with  great  sensitiveness.  If  the  surface  of  the  liquid  in 
the  tube  is  watched  during  the  action  of  the  pump,  it  is  very 
easy  to  see  that  the  volume  of  air  is  diminished  as  the  valve  D 
opens,  enlarges  for  a  moment,  and  again  contracts  after  the 
injection  has  ceased.  If  now  the  action  of  the  pump  is  so  modi- 
fied that,  after  opening  the  valve  D,  the  discharge  of  liquid  is 
continued  for  some  seconds  (both  valves  remaining  open),  we 
learn  that  the  first  expansion  is  followed  by  a  second  just  as 
before.  If  the  same  experiment  is  made  with  the  sphygmo- 
graph,  a  tracing  is  obtained  in  which  the  ascent  due  to  the  open- 
ing of  the  valve  is  succeeded  by  a  momentary  descent,  then  a 
second  ascent,  the  lever  finally  assuming  a  position  correspond- 


234  CIRCULATION    OF    THE    BLOOD. 

ing  to  the  increased  pressure  produced  by  tlie  continuous  cur- 
rent which  is  now  passing  through  the  tube. 

From  tins  experiment  we  learn,  as  regards  the  artificial 
artery,  first,  that  the  second  beat  of  the  pulse  is  not,  as  has 
been  sometimes  imagined,  a  mere  product  of  the  instrumental 
method  we  employ  to  demonstrate  it,  for  it  can  be  shown  quite 
as  distinctly  in  other  ways  ;  and  secondly,  that  it  is  a  result 
of  the  disturbance  produced  in  the  tube  by  the  sud  len  disten- 
sion of  its  proximal  end,  independently  of  any  subsequent  move- 
ment or  action  of  the  pump. 

41.  Experiments  -with  the  Schema  relating  to  the 
Form  of  the  Arterial  Pulse. — In  the  schema,  the  injection 
of  liquid  by  the  artificial  heart  into  the  proximal  end  of  the 
elastic  tube  produces  two  effects,  which  can  not  only  be  dis- 
tinguished in  the  tracing,  but  can  be  proved  experimentally  to 
be  independent  of  each  other.  One  of  these  consists  in  the 
transmission  of  a  series  of  vibratory  movements  of  the  liquid 
(t.  e.,  movements  in  alternately  opposite  directions)  from  the 
proximal  to  the  distal  end;  the  other,  in  the  communication 
of  the  pressure  existing  in  the  artificial  heart  at  the  moment 
that  the  valve  D  is  opened  to  the  contents  of  the  arterial  tube. 
The  first  of  these  effects  can  be  readily  demonstrated  on  the 
schema. 

If  you  take  an  elastic  tube,  distended  with  water,  and  closed 
at  both  ends,  and  give  it  a  smart  rap  with  a  hammer  at  one  end, 
an  effect  is  transmitted  along  the  tube  which,  although  of  an 
entirely  different  nature  to  that  which  constitutes  the  pulse,  yet 
mixes  itself  up  with  it  under  certain  conditions.  This  effect  is 
called,  from  its  mode  of  origin,  a  percussion-wave.  To  produce 
it,  close  the  communication  between  the  schematic  heart  and 
artery,  and  arrange  the  lever  (Fig.  211)  in  such  a  manner  that, 
by  striking  on  it  with  a  hammer  (at  d),  the  required  percus- 
sion may  be  produced.  The  tube  being  placed  under  the  spring 
of  the  sphj'gmograph  (at  Q),  in  such  a  position  that  the  length 
of  tubing  between  the  point  of  percussion  (d)  and  the  spring 
(o)  is  equal  to  two  metres,  a  succession  of  percussion-waves  is 
produced,  and  a  tracing  obtained  similar  to  those  shown  in  Fig. 
213,  in  which  the  interruptions  in  the  upper  line  indicate  the 
moment  of  percussion,  the  vertical  ascents  in  the  lower  line  the 
effects.  In  the  figure,  the  interval  of  time  between  cause  and 
effect  corresponds  to  the  portion  of  the  horizontal  line,  (in  the 
lower  tracing)  which  lies  between  the  short  vertical  scratch  and 
the  commencement  of  the  ascent.  The  rate  of  movement  of 
the  clock-work  during  the  experiment  being  8  centimetres  per 
minute,  this  distance  corresponds  to  about  a  fifteenth  of  a 
second. 

The  other  effect,  the  communication  of  pressure  from  the 
artificial  heart  to  the  elastic  tube,  may  be  readily  illustrated 


BY    DR.    BURLON-SANDERSON.  235 

with  the  aid  of  a  schema  in  which  the  heart  is  represented  by 
an  elastic  bag  of  such  size  that  it  can  be  squeezed  with  the  hand. 
This  bag  communicates  at  one  end  with  a  long  elastic  tube 
representing  the  arterial  system,  at  the  other  with  a  vessel  con- 
taining water,  the  apertures  being  furnished  with  valves  which 
open  in  directions  corresponding  to  those  of  the  heart.  If 
three  levers,  like  those  we  have  just  been  using,  are  so  arranged 
as  to  receive  the  successive  expansion-waves — produced  by 
repeatedly  squeezing  the  bag — at  different  distances  from  their 
origin,  the  three  tracings  are  obtained  which  are  represented 
in  Fig.  214.  It  is  instructive  to  observe  that  these  tracings  have 
no  resemblance  to  those  of  the  arterial  pulse.  The  reason  is, 
that  the  contracting  hand  is  entirety  unlike  the  contracting 
heart.  The  real  heart,  like  the  schematic  heart  used  in  the  pre- 
vious experiments,  contracts  suddenly,  exerting  its  greatest 
vigor  at  the  commencement.  The  hand  contracts  gradually, 
and  is,  moreover,  incomparably  weaker,  as  compared  with  the 
resistance  to  be  overcome,  than  the  heart.  Hence  the  expan- 
sion of  the  tube  is  slow,  lasts  a  long  time,  and  is  followed  by 
no  rebound.  This  very  slowness  of  the  process  enables  one  to 
see  the  steps  of  it  better.  In  the  distal  part  of  the  tube,  to 
which  the  upper  tracing  corresponds,  the  expansion  culminates 
later  than  in  the  proximal  part,  because  the  motion  commu- 
nicated to  its  contents  by  the  grip  of  the  hand  at  the  outset 
does  not  begin  to  tell  on  the  former  (distal)  until  the  latter  is 
fully  expanded. 

In  the  pulse  tracings  obtained  with  the  schema  arranged  as 
in  Fig.  211,  so  as  to  imitate  the  natural  pulse,  the  two  effects 
produced  in  the  preceding  experiments  separately,  are  combined 
with  each  other.  Thus  in  Fig.  212  a,  the  abrupt  initial  ascent 
of  the  lever  is  the  first  of  a  series  of  vibratory  movements  of 
the  same  kind  as  those  shown  in  Fig.  213,  and  is  instantly  fol- 
lowed by  a  recoil.  In  the  same  tracing,  the  more  gradual  ac- 
cumulation of  arterial  pressure  manifests  itself  in  the  fact  that 
the  lever  jerked  up1  by  the  vibration  does  not  (as  in  Fig.  213) 
descend  to  its  previous  position,  but  remains  elevated  for  a 
period,  which,  as  already  seen,  depends  on  the  duration  of  the 
injection  of  liquid. 

This  combination  of  effects  is  seen  with  equal  distinctness  in 
the  natural  radial  pulse.     The  abrupt  line  of  ascent  with  which 

1  In  the  sphygmographs,  lately  made  by  Bregnet,  the  movement  of 
the  spring  is  communicated  to  the  writing  lever  by  a  mechanism  shown 
in  Fi'_r.  209  b,  more  simple  and  effectual  than  that  described  on  p.  237. 
'Die  screw  is  hinged  to  the,  upper  surface  of  the  spring  in  such  a  way 
thai  it  presses  gently  against  the  axis  of  the  lever,  and  acts  upon  it  as  a 
rack  on  its  pinion.  In  this  way  the  lever  follows  the  movements  of  the 
screw  much  more  exactly,  and  the  jerk  is  diminished.  (See  Garrod  on 
Spliygmography.     Journ.  of  Anat.  and  Phys.,  May,  1872,  p.  399.) 


236  CIRCULATION  OF  THE  BLOOD. 

every  normal  tracing  begin-,  expresses  not  the  more  or  less 
gradually  increasing  arterial  distension,  but  the  antecedent 
transmission  of  a  vibration. 

42.  Postponement  of  the  Pulse. — There  is  :i  sensible  dif- 
ference in  time  between  the  beat  of  the  carotid  artery  and  that 
of  the  radial.  Any  one  can  satisfy  himself  of  the  fact  by  feel- 
ing his  own  carotid  with  the  left  thumb  and  forefinger,  while 
he  feels  the  left  radial  with  the  other  hand.  The  reason  why 
time  is  lost  in  the  transmission  of  the  expansion  from  the  centre 
to  the  periphery,  is  that  the  arteries  are  elastic.  Let  us  sup- 
pose a  tube.  A,  b,  c,  to  represent 


the  arterial  system — A  the  proximal  end,  c  the  distal.  At  the 
instant  that  blood  bursts  suddenly  out  of  the  contracting  heart 
into  a,  it  yields  to  the  pressure  against  its  internal  surface  and 
expands.  In  tins  expansion  great  part  of  the  sensible  motion 
of  the  blood  momentarily  disappears,  and  consequently,  so  long 
as  the  expansion  lasts,  produces  comparatively  very  little  effect 
in  distending  b;  but  immediately  that  A  becomes  tense,  the 
lost,  or  rather  converted,  motion  again  becomes  sensible,  and 
adds  itself  to  the  motion  which  the  contracting  heart  is  still 
communicating.  And,  inasmuch  as  B  deals  with  the  accumu- 
lated effect  which  it  receives  from  a  in  exactly  the  same  way  as 
a  dealt  with  that  which  it  received  from  the  heart,  c  is  as  far 
behind  b  in  attaining  its  maximum  of  distension  as  b  was 
behind  a.  This  being  the  case,  it  is  easy  to  see  that  the  loss 
of  time  between  A  and  c,  or  between  aorta  and  radial,  depends 
on  the  yieldingness  (extensibility)  of  the  tube  by  which  the  two 
points  are  connected.  If  the  tube  is  absolutely  rigid,  there  is 
no  postponement;  if,  though  elastic,  it  is  tense  at  the  moment 
that  it  receives  the  discharge,  there  is  scarcely  any  ;  whereas 
that  condition  of  the  tube  is  most  favorable  to  postponement, 
in  which  it  is  longest  in  attaining  its  maximum  of  distension, 
or  in  which  the  time  taken  by  any  part  of  it  to  expand  to  the 
uttermost  is  longest. 

The  preceding  explanation  relates  exclusively  to  so  much  of 
the  pulsation  as  is  due  to  the  communication  of  pressure.  As 
regards  the  antecedent  vibration-effect,  we  have  also  time  occu- 
pied in  transmission,  but  the  rate  of  propagation  is  so  rapid 
that  in  the  case  of  an  artery,  or  of  an  elastic  tube  of  similar 
length,  it  is  inappreciable.  This  fact  enables  us  to  explain 
how  it  is  that  in  some  persons  the  pulse  seems  to  be  much 
more  postponed  than  in  others.  The  reason  of  tins  is,  not  that 
there  is  more  time  lost  in  the  former  case  than  in  the  latter, 
for  even  if  this  were  so  the  difference  would  be  certainly  too 
inconsiderable  to  be  judged  of  by  the  finger,  but  that  in  some 


BY    DR.    BURDON-SANDERSON.  237 

individuals,  and  under  certain  conditions  of  health,  the  instan- 
taneously transmitted  vibration-effect  is  more  felt  by  the  fin- 
ger;  in  others,  the  moment  at  which  the  artery  attains  its 
greatest  extension.  Thus  a  pulse  of  the  form  shown  in  Fig. 
215  a  seems  to  the  finger  delayed,  because  the  vibration-effect 
is  in  abeyance  on  account  of  the  existence  of  an  obstruction 
between  the  heart  and  the  wrist;  whereas,  in  the  pulse  re- 
presented in  b,  the  initial  shock  is  so  intense  that  it  masks 
the  other. 

43.  Cause  of  the  Second  Beat. — The  facts  relating  to 
the  postponement  of  arterial  expansion  are  also  the  key  to  the 
understanding  of  the  phenomenon  of  dicrotism.  In  applying 
them  in  explanation  of  the  production  of  the  second  expansion 
in  arteries  which,  like  the  radial,  are  not  far  from  the  periphery, 
there  are  two  facts  to  be  borne  in  mind:  first,  that  these  arte- 
ries, as  they  become  smaller,  become  more  distensible;  and 
secondly,  that  in  the  capillaries  themselves  the  resistance  to 
the  passage  of  blood  is  much  greater  than  any  which  is  en- 
countered in  the  arteries.  Just  as  the  expansion  of  the  aorta 
determines  that  of  the  radial,  the  radial  expansion  determines 
and  is  followed  by  that  of  the  peripheral  arterioles.  Hence  at 
a  certain  moment  the  radial  is  subsiding,  while  the  arterioles 
are  still  swelling;  so  that,  when  they  are  at  their  acme  of  dis- 
tension, the  pressure  is  greater  at  the  periphery  than  in  the 
radial  itself.  From  the  other  fact — the  resistance  to  the  flow 
of  blood  in  the  capillaries — it  results  that,  immediately  behind 
this  resistance,  pressure  accumulates  so  long  as  blood  enters 
the  arterioles  from  behind  more  rapidly  than  it  is  discharged 
in  front.  The  state  of  the  arterial  circulation  during  the  period 
of  cardiac  diastole  may  therefore  be  described  as  follows:  The 
arterial  system  is  closed  by  the  aortic  valve  behind,  and  vir- 
tually closed  in  front  by  the  capillary  resistance.  In  the 
largest  arteries  the  expansion  is  ebbing,  in  the  smallest  it  is 
culminating;  so  that,  for  an  instant,  the  pressure  is  greater  in 
the  latter  than  in  the  former.  There  is  but  one  effect  possible. 
The  restoration  of  equilibrium  must  take  place  by  increase  of 
pressure  towards  the  heart  and  diminution  towards  the  peri- 
phery. This  restoration  of  equilibrium  constitutes  the  second 
beat.  It  may  manifest  itself  in  very  different  degrees,  accord- 
ing to  the  yieldingness  of  the  arteries.  When,  as  in  health, 
the  arteries  are  tense,  it  is  seen  merely  in  a  slight  arrest  or  in- 
terruption of  the  arterial  collapse — a  break  in  the  descending 
limb  of  the  tracing.  In  fever,  when  the  arteries  are  relatively 
much  more  distensible,  the  second  expansion  is  separated  by 
so  distinct  an  interval  of  relaxation  from  the  first  that  the  pulse 
feels  double  to  the  finger.  To  facilitate  the  comprehension  of 
the  subject,  the  S3'nchronous  conditions  of  central,  peripheral, 
and  intermediate  arteries  may  be  stated  in  parallel  columns. 


238  CIRCULATION  OF  THE  BLOOD. 

Carotid.  Ra<li;il.  Peripheral  Arterioles. 

Fully  expanded     .  Expanding     .  .  Collapsed. 

Contracting  .  Expanded       .  .  Expanding. 

Again  expanding  .  Contracting  .  .  Expanding. 

Stationaiy  .  Again  expanding  .  Slowl}-  contracting. 

Contracting  .  Contracting  .  Contracting. 

Hence,  as  sphygmographic  tracings  show  to  be  the  case,  the 
second  expansion  in  the  great  arteries  lasts  longer  than  in  the 
smaller  ones  ;  for,  although  it  commences  the  sooner  the  nearer 
the  heart,  the  subsidence  is  simultaneous  throughout  the  whole 
arterial  system. 

Rules  for  Sphygmographic  Observation. — 1.  The 
forearm  should  be  supported  on  a  table  or  other  similar  sur- 
face, with  the  back  of  the  wrist  reposing  on  a  firm,  well-padded 
cushion,  of  such  a  height  that  the  dorsal  surface  of  the  hand 
makes  an  angle  of  from  20°  to  30°  with  that  of  the  forearm. 

2.  The  spli3rgmograph  must  be  placed  on  the  wrist  in  a  di- 
rection parallel  with  that  of  the  radius,  in  such  a  position 
that  the  block  rests  upon  the  trapezium  and  scaphoid,  and 
the  extremity  of  the  spring  is  opposite  the  styloid  process  of 
the  radius. 

3.  In  beginning  an  observation,  adjust  the  instrument  so 
that  the  pressure  exerted  by  the  spring  is  sufficient  to  flatten 
the  arteiy  against  the  radius  ;  then  weaken  the  spring  until  the 
effects  of  over-compression  disappear — i.e.,  until  yon  find  that 
the  lever  continues  to  descend  until  the  end  of  diastole.  Note 
the  pressure  at  which  this  result  is  attained,  as  well  as  that 
which  is  required  to  flatten  the  artery,  and  take  tracings  at 
each  of  the  two  pressures. 

Section  III. — Phenomena  of  tiie  Circulation  in  the  smallest 

Arteries. 

The  smallest  arteries  may  be  studied  during  life  with  the 
aid  of  the  microscope,  in  fish,  batrachians,  and  mammalia. 

44.  For  the  microscopical  study  of  the  circulation  in  fish,  a 
contrivance  devised  by  Dr.  Caton,  of  Liverpool,  is  used  (fig. 
21 G).  It  consists  of  an  oblong  box  of  gutta  percha,  open  at 
one  end,  closed  at  the  other,  and  just  large  enough  to  hold  the 
bod}7  of  a  minnow  or  stickleback  very  loosely.  This  box 
forms  part  of  a  plate  of  gutta  percha,  which  is  fixed  on  to  the 
stage  of  the  microscope  in  such  a  position  that  the  tail  of  the 
fish  contained  in  it  covers  a  perforation  in  the  plate  prepared 
for  its  reception.  The  tail  is  held  securely  in  its  place  b}r  a 
ligature,  and  the  caudal  fin  which  rests  on  a  square  of  glass  is 
further  secured  by  a  couple  of  fine  springs.  The  box  itself, 
which  incloses  the  head  and  gills  of  the  fish,  contains  water, 
which  is  constantly  renewed  by  means  of  the  two  tubes,  of 


BY    DR.    BURB-ON-SANDERSON.  289 

■which  the  upper,  guarded  by  a  screw-clamp,  communicates 
"with  a  vessel  at  a  higher  level,  the  lower  conveys  the  water 
away  as  fast  as  it  is  supplied.  The  excellency  of  this  method 
lies  in  the  fact  that  the  animal  can  be  kept  under  observation, 
without  the  use  of  any  narcotizing  drug,  for  a  long  time  in  a 
perfectly  natural  condition.  The  frog  is  used  both  in  the  larval 
and  adult  state.  To  observe  the  circulation  in  the  tail  of  the 
tadpole,  the  animal  is  placed  in  a  moderately  strong  solution 
of  curare,  care  being  taken  to  remove  it  before  it  is  completely 
paralyzed — the  moment,  in  short,  that  its  motions  become 
sluggish.  It  is  also  possible  to  secure  it,  without  the  aid  of 
curare,  in  a  holder  of  construction  similar  to  that  of  the  in- 
strument I  have  just  described — a  method  which  has  this  great 
advantage,  that  the  animal  is  in  a  more  normal  condition ;  for 
even  when  curare  is  given  with  the  greatest  care,  the  action 
of  the  heart  is  weakened  by  it.  For  most  purposes  the  adult 
frog  is  more  useful  than  the  tadpole,  particularly  when  it  is 
desired  to  observe  not  merely  the  circulation  as  it  is,  but  to 
witness  the  modifications  which  the  phenomena  undergo  under 
the  influence  of  conditions  acting  on  the  bloodvessels  through 
the  nervous  sj'stem. 

There  are  three  transparent  parts  of  the  frog — the  mesen- 
tery, the  web,  and  the  tongue — each  of  which  has  its  special 
advantages  for  the  purposes  of  study.  For  a  first  view  of  the 
relation  between  arteries,  capillaries,  veins,  and  lymphatics,  the 
mesentery  is  superior  to  either  of  the  other  two.  The  frog 
must  be  placed  under  the  influence  of  curare,  the  dose  of 
which,  for  the  ordinary  specimens  of  rana  temporaria,  is  about 
smooth  of  a  grain.  The  solution  of  curare  is  prepared  by 
weighing  out  five  milligrammes  of  the  substance,  and  rubbing 
it  up  in  a  glass  mortar  with  a  little  alcohol.  The  proper 
quantity  of  water — that  is,  sufficient  to  make  up  ten  cubic 
centimetres — is  then  added,  and  a  straw-colored,  nearly  limpid 
liquid  is  obtained,  a  single  drop  of  which  is  a  sufficient  dose. 
It  is  injected  under  the  skin  of  the  back  with  an  ordinary 
subcutaneous  syringe,  and  answers  best  when  the  effect  does 
not  manifest  itself  for  some  time  after  the  injection.  The 
most  convenient  apparatus  for  the  purpose  of  exposing  the 
mesentery  is  that  shown  in  fig.  21*7.  The  manipulation  is  ; 
fully  described  in  Chapter  VII.  It  is  always  desirable  to 
commence  the  examination  with  a  low  power.  It  is  then  seen 
that  the  arteries  are  smaller  than  the  veins,  the  latter  exceed- 
ing the  former  in  diameter  by  about  a  sixth  ;  that  the  arterial 
stream  is  quicker  than  the  venous ;  that  it  is  accelerated 
appreciably  at  each  beat  of  the  heart ;  and  that  in  every 
artery  a  space  can  be  distinguished  within  the  outline  of  the 
vessel,  which  is  entirely  free  from  corpuscles.  The  arterial 
stream,  indeed,  is  so  quick  that  the  forms  of  the  corpuscles 


2-40  CIRCULATION   OF    THE    BLOOD. 

cannot  be  discerned,  but  in  the  veins  both  colored  and  color- 
less corpuscles  can  be  distinguished  ;  and  it  is  soon  noticeable 
that,  while  the  former  are  confined  to  the  axial  current,  the 
latter  show  a  tendency  to  loiter  along  the  inner  surface  of  the 
vessel, like  round  pebbles  in  a  shallow  but  rapid  stream.  The 
observation  may  be  continued  without  material  change  for 
many  hours;  but  if  any  artery  is  measured  from  time  to  time 
micrometrically,  it  will  be  found  that  after  a  while  it  becomes 
wider.  On  this  dilatation  of  the  arteries  follows  a  correspond- 
ing though  less  marked  enlargement  of  the  veins,  and,  if  the 
attention  of  the  observer  is  fixed  upon  these  last,  it  is  seen 
that  the  circulation,  which  was  before  so  active,  undergoes  a 
marked  and  almost  sudden  slowing.  This  slowing  indicates 
that  the  membrane,  in  consequence  of  its  exposure  to  the  air, 
is  becoming  inflamed;  simultaneously  with  it,  the  colorless 
corpuscles,  instead  of  loitering  here  and  there  at  the  edge  of 
the  axial  current,  crowd  in  numbers  against  the  venous  walls. 
In  this  way  the  vessel  becomes  lined  with  a  continuous  pave- 
ment of  these  bodies,  which  remain  almost  motionless,  not- 
withstanding that  the  axial  current  still  sweeps  by  them, 
though  with  abated  velocity.  If,  at  this  moment  the  atten- 
tion is  directed  to  the  outer  contour  of  the  vessel,  it  is  seen 
that  minute,  colorless,  button-shaped  elevations  spring  from  it, 
each  of  which  first  assumes  the  form  of  a  hemispherical  pro- 
jection, and  is  eventually  converted  into  a  pear-shaped  body, 
attached  by  a  stalk  to  the  outer  surface  of  the  vein.  This 
body,  which  has  thus  made  its  way  through  the  vascular  mem- 
brane, is,  I  need  scarcely  say,  an  amceboid  colorless  corpuscle. 
It  soon  shows  itself  to  be  so  by  throwing  out  delicate  prongs 
of  transparent  protoplasm  from  its  surface,  especially  in  the 
direction  from  which  it  has  come. 

The  methods  to  be  employed  for  the  study  of  the  circulation 
in  the  tongue  and  in  the  web  are  fully  described  in  Chapter 
VII.  For  investigations  relating  to  the  innervation  and  con- 
tractile movements  of  the  smallest  arteries,  the  tongue  is  of 
little  value,  though  superior  to  the  mesentery  and  web  for  the 
study  of  inflammation.  The  web,  on  the  other  hand,  is  pre- 
ferable, for  the  purposes  first  mentioned,  to  either  the  tongue 
or  mesentery. 

45.  Capillary  Circulation  in  Mammalia. — The  study 
of  the  capillary  circulation  of  mammalia  under  the  micro- 
scope is  attended  with  great  difficulty — in  the  first  place,  be- 
cause (if  we  except  the  wing  of  the  bat)  there  is  no  external 
part  sufficiently  transparent  for  observation  under  high  power  ; 
and,  secondly,  because  if  internal  parts  are  used,  the  injurious 
effects  of  exposure  are  much  greater  than  those  which  occur 
in  batrachians.     To  overcome  these  difficulties  it  is  necessary 


BY    DR.    BURDON-SANDERSON.  241 

to  have  recourse  to  more  complicated  appliances  and  appa- 
ratus. 

The  mesenteries  of  small  rodents  have  been  repeatedly  used 
for  the  demonstration  of  the  mammalian  capillary  circulation. 
These,  however,  are  not  to  be  compared,  as  subjects  of  obser- 
vation, with  the  omentum,  and  particularly  with  that  of  the 
guineapig.  This  structure  forms  a  delicate  membranous  ex- 
pansion of  from  twelve  to  fifteen  cubic  centimetres  in  extent, 
which  is  attached  by  its  upper  margin  to  the  greater  curvature 
of  the  stomach.  It  differs  from  the  organ  of  the  same  name  in 
man  in  consisting,  for  the  most  part,  of  only  two  la}rers  of 
peritonaeum,  in  being  much  more  delicate  in  its  structure,  and 
containing  very  little  fat.  Hence,  from  the  simplicity  of  the 
anatomical  relations,  and  particularly  from  its  being  attached 
by  one  side  only  to  the  stomach,  from  its  perfect  transparency, 
from  its  abundant  vascularity,  and,  lastly,  from  its  containing 
not  only  vessels  but  living  cells,  it  is  obvious  that  this  mem- 
brane offers  a  good  field  for  research. 

The  observations  hitherto  made  on  the  mammalian  mesen- 
tery have  been  without  practical  result,  the  reason  being  that 
so  vulnerable  a  tissue  as  that  of  the  peritonaeum  cannot  be 
exposed,  even  for  a  few  minutes,  without  injury;  so  that, 
although  the  greatest  care  is  taken  in  demonstration,  only  a 
momentary  glimpse  can  be  obtained.  To  obviate  this  difficulty, 
the  arrangements  for  placing  the  membrane  under  the  micro- 
scope must  be  of  such  a  nature,  that  the  structure  is  bathed 
during  the  whole  period  of  observation  in  a  liquid  at  the  tem- 
perature of  the  body.  It  need  scarcely  be  said  that  water, 
from  its  destructive  influence  on  living  tissues,  would  not 
answer  the  purpose.  Serum  would  probably  be  best,  if  it  were 
always  at  hand  ;  but,  practically,  solution  of  common  salt  of 
the  strength  ordinarily  used  (f  per  cent.)  answers  the  purpose 
perfectly.  The  temperature  is  maintained  by  keeping  the 
glass  trough,  in  which  the  membrane  is  spread  out,  over  the 
warm  stage,  the  construction  of  which  has  been  already  de- 
scribed. 

The  mode  of  procedure  is  as  follows:  The  guineapig  is  first 
placed  under  the  influence  of  chloral  by  injecting  that  sub- 
stance in  solution  under  the  skin,  three  grains  being  required 
for  an  animal  about  lib.  in  weight.  It  is  then  laid  on  a  sup- 
port, the  upper  surface  of  which  is  on  the  same  horizontal 
plane  as  that  of  the  microscope-stage.  An  incision  not  more 
than  an  inch  in  length  is  next  made,  extending  outwards  from 
the  edge  of  the  left  rectus  muscle  a  little  below  the  end  of  the 
ensiform  cartilage.  The  muscles  having  been  divided,  and  the 
peritonaeum  cautiously  opened  for  about  half  an  inch,  or  even 
less,  the  free  edge  of  the  omentum  is  carefully  drawn  out.  It 
must  then  be  floated  in  the  warm  bath  prepared  for  it,  and  is 
16 


242  CIRCULATION  OF  THE  BLOOD. 

ready  for  examination.  Tt  is,  however,  found  very  advanta- 
geous to  cover  those  parts  of  it  which  do  not  lie  under  the 
microscope  with  sheets  of  blotting-paper,  for  by  this  means 
the  risk  of  exposure  is  diminished,  and  the  undulating  move- 
ments of  the  water  are  prevented  ;  so  that  the  object  is 
rendered  much  steadier  than  it  would  otherwise  be.  So  long 
as  low  powers  are  employed,  this  arrangement  is  sufficient ; 
but  if  it  is  desired  to  use  objectives  of  short  focal  distance,  it 
is  necessary  to  warm  the  objective  by  allowing  a  stream  of 
water  from  the  same  source  as  that  which  supplies  the  stage 
to  pass  round  it. 

The  objects  which  present  themselves  to  the  observer  are 
manifold.  Veins  and  arteries  may  be  studied  of  various  di- 
ameters, some  of  which  are  free,  while  others  are  surrounded 
by  sheaths  of  tissue  in  which  there  are  lab}-rinths  of  capillaries 
of  surpassing  beauty.  Several  new  observations  have  already 
been  made  by  this  method.  One  of  the  most  important,  phy- 
siologicallj-,  is  the  fact  that  the  maintenance  of  the  capillary 
circulation  is  wonderfully  dependent  on  temperature ;  and,  in 
particular,  that  any  rise  of  temperature  above  the  normal  is  in 
the  highest  degree  injurious,  parti}',  perhaps,  from  its  direct 
influence  on  the  blood  corpuscles,  but  mainly  because  it  pro- 
duces changes  similiar  to  those  we  have  already  noticed  as 
occurring  in  batrachians  after  long  exposure — viz.,  arrest  of 
the  capillary  blood-stream  and  escape  of  the  liquor  sanguinis 
and  corpuscles  into  the  surrounding  tissue. 

46.  Artificial  Circulation. — For  many  purposes  of  re- 
search, it  is  desirable  to  observe  the  circulation  independently 
of  the  action  of  the  heart.  This  is  accomplished  either  in  the 
whole  body  or  in  an  organ,  by  injecting  blood,  or  a  liquid 
which  may  be  substituted  for  it,  in  a  constant  stream  into  the 
arterial  system,  at  the  same  temperature  and  under  the  same 
pressure  as  that  which  naturally  exists  in  the  arteries.  In  the 
case  of  batrachians,  this  is  accomplished  without  difficulty, 
for  the  temperature  of  the  bod}'  differs  little  from  that  of  the 
atmosphere,  and  the  nutritive  processes  can  be  maintained  for 
long  periods,  not  only  without  respiration,  but  without  the 
agent  by  which  oxygen  is  combed  to  the  tissues — haemoglo- 
bin. Consequently  the  conditions  to  be  observed  are  very 
simple.     The  requirements  for  the  purpose  are  as  follows: — 

1.  The  liquid  to  be  injected  may  be  either  serum,  defibri- 
nated  blood,  or  f  per  cent,  solution  of  chloride  of  sodium. 
When  serum  is  used,  it  must  be  absolutely  fresh.  For  this 
reason,  the  serum  obtained  from  the  slaughter-house  is  usually 
not  to  be  depended  upon.  It  is  therefore  necessary  to  use  a 
small  rabbit  for  the  purpose.  In  order  to  obtain  a  sufficient 
quantity  of  blood  from  this  animal,  a  canula  must  be  care- 
fully secured  in  the  carotid,  and  a  clip   placed  on  the   artery. 


BY   DR.    BURDON-SANDERSON.  243 

The  connector  adapted  to  the  canula  must  be  of  sufficient 
length  to  reach  an  absolutely  clean  flask  or  capsule  destined 
for  the  reception  of  the  blood.  If  serum  is  required,  the  cap- 
sule must  be  allowed  to  stand  in  a  cool  place  until  it  is  coagu- 
lated. If  defibrinated  blood,  the  flask  must  be  agitated  brisk- 
ly imniediateby  after  it  is  collected.  The  blood  should  be  taken 
in  successive  portions,  for  in  this  way  a  much  larger  quantity 
is  obtained  than  would  be  yielded  if  the  animal  were  allowed 
to  bleed  to  death  at  once. 

2.  The  apparatus  for  injection  consists  of  a  funnel,  supported 
on  a  holder  at  a  height  of  about  two  feet  from  the  table,  to 
the  stem  of  which  a  flexible  tube,  guarded  by  a  clip,  is  adapt- 
ed. In  addition  to  this,  two  Canute  must  be  prepared,  one 
for  the  bulbus  arteriosus,  the  other  for  the  vena  cava  inferior. 
Both  should  be  made  of  thin  fusible  glass,  and  of  the  size  and 
form  shown  in  figure  218.  The  arterial  canula  must  be  con- 
nected by  an  India-rubber  tube  of  the  same  width  as  itself 
with  a  glass  joiner,  and  its  end  must  be  supported  by  a  holder 
which  can  be  best  made  of  a  strip  of  sheet  lead  bent  to  the 
proper  form.  The  funnel  having  been  filled  with  the  liquid 
to  be  injected,  and  connected  with  the  canula  by  the  joiner,  a 
sufficient  quantity  is  allowed  to  flow  into  the  tube  to  occupy 
it  completely,  and  the  clip  closed.  All  being  now  ready,  a 
frog,  previously  slightly  curarized,  is  fixed  on  the  table  in  the 
supine  position.  The  integument  is  divided  over  the  sternum 
in  the  middle  line,  and  the  anterior  wall  of  the  upper  part  of 
the  visceral  cavity  removed,  so  as  to  expose  the  pericardium, 
great  care  being  taken  not  to  injure  the  abdominal  vein,  or 
any  other  large  vessel.  The  ventricle  is  then  opened,  and  the 
canula  passed  through  the  opening  into  the  bulb,  and  secured 
b}'  a  ligature.  This  done,  the  heart  is  drawn  upwards,  and  to 
the  right  (after  severance  of  the  small  vein  which  stretches 
from  the  back  of  the  ventricle  to  the  pericardium),  so  as  to 
expose  the  sinus  venosus,  which  is  then  opened  in  the  line  of 
junction  between  it  and  the  auricles.  By  this  opening,  the 
canula  for  the  vena  cava  is  easily  introduced  into  the  funnel- 
shaped  dilatation  (see  fig.  228  6),  and  pushed  into  the  vein. 
If  the  canula  is  of  proper  size,  a  ligature  is  unnecessary.  On 
opening  the  clip  on  the  tube  leading  from  the  funnel,  the  cir- 
culation is  restored.  The  blood  contained  in  the  vascular 
system  of  the  animal  is  soon  replaced  by  the  liquid  injected. 

The  most  instructive  observations,  relating  to  frogs  in 
which  the  circulation  is  maintained  artificially  (sometimes 
called  salt  or  serum  frogs,  according  to  the  liquid  used),  are 
made  with  the  aid  of  the  microscope.  The  examination  of  the 
web  shows  us  that  even  when  saline  solution  is  used,  the  ves- 
sels and  the  circulation  through  them  remain  unaltered  for 
some  time.     If  serum  is  used,  this  period  is  longer,  provided 


244  CIRCULATION    OF   THE    BLOOD. 

that  it  is  perfectly  fresh.  A  very  slight  admixture,  however, 
of  kept  scrum  is  fatal  to  the  experiment.  After  a  time,  de- 
cline of  tissue  life  manifests  itself  by  a  change  in  the  appear- 
ance of  the  preparation,  the  elements  losing  their  plumpness 
and  distinctness  of  outline.  Along  with  this  change,  the  ves- 
sels, and  particularly  the  arteries,  become  relaxed,  and  the 
normal  exchange  between  the  liquid  inside  and  that  outside 
of  the  vessels  is  perverted,  the  latter  increasing  in  such  a  way 
as  to  render  the  whole  animal  oedematous. 

If,  while  the  circulation  is  still  normal,  an  injur}'  is  inflicted 
on  a  part  of  the  web — as,  for  example,  by  applying  mustard 
to  a  spot  on  its  surface — it  is  seen  that  in  the  injured  part 
changes  occur  suddenly  which  are  analogous  to  those  which, 
as  tissue  death  approaches,  affect  the  whole  bod}'.  These 
changes  are  known  by  the  term  stasis,  and  form  part  of  the 
process  of  inflammation — a  word  which  is  used  as  a  general 
expression  for  the  local  effects  of  injuring  living  parts  to  such 
a  degree  as  not  to  destroy  their  vitality  at  once.  They  are 
best  studied  when  serum  which  contains  a  few  corpuscles,  or 
defibrinated  blood  diluted  with  saline  solution,  is  employed. 
It  is  then  seen  that  in  any  part  of  the  web  to  which  a  so-called 
irritant  is  applied,  as,  e.  g.,  mustard — the  blood  stream  is  re- 
tarded, and  the  corpuscles  crowd  together  in  the  dilated  ves- 
sels. This  is  not  due  to  any  property  of  mutual  attraction 
peculiar  to  the  corpuscles,  for  the  same  thing  happens  if  milk, 
diluted  with  saline  solution,  is  substituted  for  blood  ;  so  that, 
whatever  be  the  nature  of  the  change,  its  seat  is  not  in  the 
circulating  liquid  itself,  but  in  the  vessels  or  surrounding  tis- 
sues. 

Section  IV. — Functions  of  Vasomotor  Nerves. 

In  the  proceeding  section  the  arteries  have  been  regarded 
merely  as  passive  elastic  tubes,  dilating  or  contracting  accord- 
ing to  the  pressure  exercised  upon  them  by  the  circulating 
blood.  They  must  now  be  studied  as  not  only  elastic  but 
contractile. 

The  arteries  owe  their  contractility  to  the  unstriped  muscu- 
lar fibres  which  they  contain.  These  fibres  shorten  under  the 
influence  of  impressions  conveyed  to  them  by  the  vascular 
nerves,  which  nerves,  together  with  the  automatic  centre  from 
which  they  radiate,  constitute  the  vasomotor  nervous  system. 
Of  the  centre  which  governs  arterial  contraction,  nothing  is 
known  anatomically  ;  for  there  is  no  point  or  tract  in  the  brain 
or  spinal  cord  to  which  vascular  nerves  can  be  traced  back. 
All  that  is  known  has  been  learnt  exclusively  by  experiment. 

That  there  is  a  vasamotor  centre,  and  that  it  is  intracranial, 
we  learn  by  observing,  first,  that  if  the  medulla  is  divided  im- 


BY    DR.    BURDON-SANDERSON.  245 

mediately  below  the  cerebellum,  all  the  arteries  are  relaxed, 
and  that  a  similar  effect  is  produced  if  certain  afferent  nerve 
fibres,  which  lead  to  the  intracranial  part  of  the  cord,  are  ex- 
cited. Its  position  has  been  lately  determined  with  great  pre- 
cision in  the  rabbit  by  Ludwig  and  Owsjannikow,  who  have 
found  by  experiments,  to  which  further  reference  will  be  made, 
that  it  is  limited  towards  the  spinal  cord  by  a  line  four  or  five 
millimetres  above  the  calamus  scriptorius,  and  extends 
towards  the  brain  to  within  a  millimetre  of  the  corpora 
quadrigemina. 

That  the  vasomotor  centre  is  in  constant  automatic  action, 
is  shown  b}'  the  paralyzing  effect  of  section,  whether  of  the 
spinal  cord,  or  of  any  nerve  known  to  contain  vascular  fibres. 
If  the  action  of  the  centre  were  not  constant,  division  could 
not  produce  arterial  relaxation.  In  relation  to  this  constancy 
of  action,  the  word  tonus  is  used.  Arterial  tonus  means  that 
degree  of  contraction  of  an  artery  which  is  constant  and  nor- 
mal. It  is  maintained  only  so  long  as  the  artery  is  in  com- 
munication with  the  vaso-motor  centre. 

47.  Experiments  relating  to  the  Influence  of  the 
Cerebro-Spinal  Nervous  Centres  of  the  Vascular  Sys- 
tem.— (1.)  Destruction  of  the  Nervous  Centres. — Two 
frogs  are  slightly  curarized,  and  placed  side  by  side  on  the 
same  board,  in  the  supine  position.  In  both,  the  heart  and 
great  vessels  are  exposed,  as  in  the  preceding  section.  It 
having  been  ascertained  that  the  circulation  is  normal  in  each 
animal,  and  the  frequency  of  the  contractions  having  been 
noted,  the  brain  and  spinal  cord  are  destined  in  one  of  the 
frogs,  Iry  inserting  a  strong  needle  into  the  spinal  canal  imme- 
diately below  the  occipital  bone,  and  then  passing  it  upwards 
and  downwards.  This  may  usually  be  accomplished  without 
much  loss  of  blood.  If  now  the  frog  which  has  been  deprived 
of  its  nervous  centres  is  compared  with  the  other,  it  is  seen 
that  in  the  former,  although  the  heart  is  beating  with  perfect 
regularity  and  unaltered  frequency,  it  is  empty,  and  in  conse- 
quence, instead  of  projecting  from  the  opening  in  the  anterior 
wall  of  the  chest,  it  is  withdrawn  upwards  and  backwards 
towards  the  oesophagus. 

The  emptiness  of  the  heart  is  not  limited  to  the  ventricle  and 
bulb.  The  auricles  are  alike  deprived  of  blood ;  and  if  the 
heart  is  drawn  forwards  by  the  apex,  it  is  seen  that  the  sinus 
venosus  and  vena  cava  inferior  are  in  the  same  condition. 
The  state  of  the  heart  is  therefore  not  dependent  on  any  cause 
inherent  in  itself,  but  on  the  fact  that  no  blood  is  conveyed  to 
it  by  the  veins.  To  make  this  still  more  evident,  the  rest  of 
the  visceral  cavity  may  be  opened,  when  it  is  seen  that,  although 
the  vena  cava  is  collapsed,  the  intestinal  veins  are  distended. 
The  second  frog,  which  is  no  longer  required  for  comparison, 


246  CIRCULATION    OF   THE    BLOOD. 

should  now  be  pithed  in  the  same  manner  as  the  first.  A 
canula  is  then  introduced  into  the  abdominal  vein,  with  its 
orifice  towards  the  heart,  and  connected,  by  an  India-rubber 
tube  guarded  by  a  clip,  with  a  funnel  containing  three-fourths 
per  cent,  solution  of  chloride  of  sodium.  The  heart  having 
been  exposed,  and  its  empty  condition  noted,  the  clip  is 
opened.  Its  cavities  at  once  distend,  and  it  acts  as  vigorously 
and  effectually  as  before  the  destruction  of  the  nervous  cen- 
tres. The  experiment  may  be  varied  thus :  Two  frogs  are 
suspended  side  by  side,  one  of  which  has  been  pithed  in  the 
manner  above  described.  In  both,  the  heart  is  exposed  and 
the  ventricle  cut  across.  In  the  pithed  frog,  a  small  quantity 
of  blood  escapes,  the  quantity  contained  in  the  heart  itself  and 
the  commencement  of  the  arterial  system.  In  the  other,  blood 
continues  to  flow  for  some  minutes,  in  consequence  of  the  con- 
tinued contraction  of  the  arterial  system.  To  what  extent  the 
veins  may  participate  in  it  is  uncertain. 

These  simple  experiments  show,  first,  that  in  the  frog  the 
arteries,  unaided  by  the  heart,  continue  the  circulation  for  a 
certain  time  after  equilibrium  of  pressure  has  been  established, 
by  virtue  of  their  contractility  ;  and  secondly,  that  in  this  ani- 
mal the  influence  of  arterial  contractility  in  aid  of  the  circula- 
tion is  so  considerable  that,  when  it  is  abolished,  circulation  is 
no  longer  possible. 

It  may  be  well  to  point  out  that  this  fact  affords  no  ground 
for  supposing  that  the  arteries  take  any  active  part  in  main- 
taining the  circulation.  All  that  is  proved  is,  that  in  the  re- 
laxed state  the  vascular  system  of  the  frog  is  relatively  so 
capacious  that  it  is  more  than  large  enough  to  contain  the 
whole  mass  of  the  blood,  which  consequently  comes  to  rest  in 
it  out  of  reach  of  the  influence  of  the  heart.  During  life,  the 
arterial  tonus  is  usually  constant ;  so  long  as,  and  in  so  far  as 
this  is  the  case,  the  function  of  the  arteries  is  a  passive  one, 
the  motion  they  give  to  the  blood-stream  during  diastole  being 
a  mere  restitution  of  that  received  by  them  from  the  heart 
during  systole.  On  the  other  hand,  whenever  they  contract, 
they  originate  motion  of  themselves  ;  but  in  this  case  the  dura- 
tion of  the  effect  is  limited  by  that  of  the  contraction,  and  can 
never  be  continuous. 

48.  (2.)  Direct  Excitation  of  the  Spinal  Cord  in  the 
Frog. — The  requirements  are  as  follows  :  a.  A  thin  board  of 
soft  wood  about  8  inches  long  and  2  inches  broad,  one  end  of 
which  has  a  V-shaped  notch  cut  out  of  it,  corresponding  in  form 
and  size  to  one  of  the  interdigital  membranes  of  the  web  of  the 
frog's  foot.  b.  A  pair  of  common  strong  sewing-needles ; 
around  the  blunt  end  of  each  of  these  needles,  the  end  of  a 
length  of  thin  copper  wire  is  closely  coiled  ;  they  are  then  cov- 
ered nearly  to  their  points  with  a  protective  and  insulating 


BY    DR.    BURDON-SANDERSON.  247 

coating  of  soft  sealing-wax,  for  which  purpose  it  is  necessary 
to  warm  them  in  the  flame  of  a  lamp.  In  doing  this,  care  must 
be  taken  not  to  heat  the  point,  c.  A  battery  and  Du  Bois's 
induction  apparatus  and  key.  The  key  must  be  interposed  in 
the  secondary  circuit. 

A  frog  having  been  curarized  just  sufficiently  to  paralyze  its 
voluntary  muscles,  a  straight  line  is  drawn  from  the  notch 
along  the  upper  surface  of  the  board  in  a  direction  parallel  to 
its  edges.  Two  small  perforations  are  made  in  this  line,  a 
couple  of  millimetres  from  each  other,  at  a  distance  from  the 
notch  equal  to  that  from  the  web  of  the  frog  to  its  occiput. 
Through  these  perforations  the  needles  are  thrust,  so  as  to  pro- 
ject about  5  millimetres,  after  which  the  board  is  arranged  in 
such  a  way  on  the  microscope,  that  the  V-shaped  notch  rests 
over  the  stage  aperture,  and  the  opposite  end  on  a  support  at 
the  same  level.  All  being  now  ready,  the  integument  is  opened 
along  the  middle  line  of  the  back  of  the  neck,  and  the  occipital 
bone  perforated  in  the  middle  line  with  a  fine  awl,  close  to  its 
posterior  margin.  The  frog  is  then  laid,  back  downwards  on 
the  board,  in  such  a  position  that  one  of  the  needles  enters  the 
cranium  through  the  hole  in  the  occipital  bone,  the  other  the 
spinal  canal.  The  web  is  then  laid  on  a  plate  of  glass  which 
covers  the  notch,  and  secured  if  necessary  by  fine  pins.  Finally, 
the  heart  is  exposed  as  before. 

On  opening  the  key  for  a  moment,  so  as  to  allow  the  induced 
current  to  pass  through  the  needles,  it  is  seen  that  all  the  arte- 
ries of  the  web  at  once  contract,  the  contraction  increasing  for 
four  or  five  seconds  and  then  gradually  subsiding.  If  the  ex- 
citation is  continued  for  several  seconds,  the  circulation  stops. 
To  judge  of  the  effect  accurately,  it  is  desirable,  first,  to  fix 
upon  an  artery  for  observation  beforehand,  and  bring  it  well 
into  view  ;  and  secondly,  to  measure  its  diameter  before,  during, 
and  after  excitation.  For  this  purpose,  a  sheet  of  paper  is 
placed  on  a  board  in  such  a  position  that  its  surface  is  at  right 
angles  to  the  direction  in  which  the  image  is  thrown  by  the 
prism  (see  fig.  219),  and  at  a  distance  of  about  10  inches  from 
it.  The  outlines  of  the  vessel  are  then  traced  on  the  paper  with 
a  fine  hard  pencil.  During  and  after  excitation,  other  tracings 
are  made  in  the  same  way ;  by  comparison  of  which  the  changes 
of  the  diameter  of  the  vessel  can  be  accurately  estimated.  The 
microscope  must  of  course  be  so  placed  that  light  is  received 
from  the  side,  and  that  the  surface  of  the  paper  is  sufficiently 
illuminated  to  enable  the  observer  to  distinguish  the  point  of 
the  pencil.  To  insure  success  in  this  fundamental  experiment, 
the  following  precautions  must  be  attended  to.  The  dose  of 
curare  must  be  very  small,  and  should  therefore  be  given  an 
hour  or  two  before  the  observation  is  made.  One  at  least  of 
the  electrodes  must  be  inserted  within  the  cranium  :  for  if  both 


248  CIRCULATION    OF    THE    BLOOD. 

are  lielow  the  occipital  bone,  the  effect  is  uncertain.  Lastly, 
great  cart'  must  be  taken  to  use  feeble  currents,  and  not  to  pro- 
long the  excitations,  for  the  vasomotor  nervous  system  of  the 
frog  is  very  readily  exhausted. 

49.  (3.)  Excitation  and  Section  of  the  Spinal  Cord  in 
the  Rabbit. — The  requirements  and  preliminary  preparation 
for  this  experiment  are  the  following :  A  canula  and  subcuta- 
neous syringe  for  injecting  20  per  cent,  solution  of  curare  into 
the  jugular  vein  ;  apparatus  for  a  kymographic  observation  of 
arterial  pressure  ;  apparatus  for  artificial  respiration  ;  a  needle 
for  ligaturing  the  muscles,  in  addition  to  the  ordinary  instru- 
ments. The  canula  for  the  jugular  is  shown  in  fig.  220  An 
India-rubber  tube  is  fitted  to  it,  the  end  of  which  is  closed  by  a 
ligature.  It  is  inserted  as  follows:  The  rabbit  having  been 
placed  in  the  usual  way  on  Czermak's  rabbit  supporter,  with 
the  cushion  under  its  neck,  the  integument  is  divided  in  the 
middle  line  from  the  pomum  Adami  downwards,  as  directed  in 
Section  I.  On  drawing  the  edge  of  the  incision  to  either  side, 
the  jugular  vein  is  readily  seen  as  it  crosses  the  sterno-mastoid. 
It  is  then  carefully  cleared  of  the  platysma  fibres  and  fascia 
which  cover  it,  and  of  its  sheath  to  the  extent  of  an  inch  or 
more,  with  the  aid  of  two  pairs  of  blunt  forceps.  A  clip  having 
been  placed  on  the  proximal  end  of  the  cleared  part,  a  ligature 
is  looped  round  the  distal  end,  which  is  tightened  as  soon  as 
it  is  seen  that  the  vein  is  distended.  This  being  accomplished, 
a  second  ligature  is  placed  round  the  vessel  between  the  first 
ligature  and  the  clip,  and  then  a  V-shaped  incision  is  made  in 
the  vein  immediately  beyond  it.  Finally,  the  canula,  which  has 
been  previously  filled  with  saline  solution,  is  slipped  into  the 
vein  and  secured  in  its  place  by  the  ligature  prepared  for  it. 
When  it  is  intended  to  inject,  the  point  of  the  subcutaneous 
syringe  is  shrust  through  the  closed  tube  of  India-rubber.  On 
withdrawing  it  no  liquid  escapes.  The  plan  has  the  advantage 
that  successive  quantities  may  be  injected  with  the  greatest 
facility.  The  mode  of  preparing  the  carotid  artery,  and  of  con- 
necting it  with  the  kymographic  canula,  has  been  described  in 
§  34.  For  the  present  purpose  it  is  necessary  to  free  the  artery 
from  its  connections  to  a  greater  extent  than  usual.  The  canula 
having  been  secured  in  the  artery, and  the  latter  divided  beyond 
the  point  of  insertion,  the  canula  is  turned  back  and  fixed  to 
the  animal's  thorax  (by  tying  it  to  the  fur)  in  such  a  position 
that  the  artery  forms  a  loop,  with  its  convexity  towards  the 
head.  The  purpose  of  this  arrangement  is  to  prevent  the  artery 
from  being  strained  when  the  animal  is  turned.  The  apparatus 
for  artificial  respiration  has  not  yet  been  described.  It  is  re- 
quired because  the  animal  being  under  the  influence  of  curare, 
its  voluntary  muscles  are  paralyzed.  Asa  substitute  for  natu- 
ral breathing,  air  must  be  injected  in  the  proper  quantity  at 


BY    DR.    BURDON-SANDERSON.  249 

regular  intervals,  which  correspond  with  the  previous  frequency 
of  the  respiratory  acts.  In  the  absence  of  self-acting  apparatus, 
the  best  instrument  to  use  is  the  caoutchouc  blower  and  ex- 
panding regulator  sold  by  Messrs.  Griffin  for  working  the  gas 
blow-pipe  (see  fig.  221).  The  blower  is  worked  by  means  of  a 
squeezer.  It  consists  of  an  oblong  board  or  lever,  16  inches 
long,  3  inches  wide,  and  f  inch  thick.  This  board  is  hinged  in 
the  middle  to  a  fulcrum,  in  such  a  way  as  to  admit  of  a  see-saw 
movement.  The  fulcrum  is  firmly  screwed  to  the  table.  When 
it  is  in  use,  the  blower  is  placed  under  one  end,  i.  e.,  between 
it  and  the  table,  the  degree  of  compression  being  limited  by  a 
strong  cord  attached  at  the  opposite  end  to  the  table.  By 
varj'ing  the  length  of  the  cord,  the  quantity  of  air  injected  at 
each  stroke  is  regulated.  The  blower  communicates  with  the 
respiratory  cavity  by  a  tracheal  canula.  No  valve  is  required, 
the  expired  air  passing  out  freely  during  the  intervals  between 
each  injection  and  its  successor,  by  a  hole  in  the  tube.  The 
quantity  of  air  discharged  by  the  blower  at  each  stroke  must, 
therefore,  considerably  exceed  the  quantity  which  is  required 
for  respiration.  This  contrivance  can  be  worked  with  much 
less  fatigue  than  bellows.  The  time  must  be  regulated  by  a 
metronome.  The  self-acting  appa?*atas  consists  of  two  parts 
— a  constantly  acting  blower  or  expirator,  and  an  arrange- 
ment for  interrupting  the  current  of  air  at  regular  intervals. 
The  best  constant  blower  is  that  known  as  Sprengel's  blowpipe,1 
the  structure  of  which  will  be  understood  at  once  from  fig.  222. 
The  essential  part  of  it  is  the  vertical  tube  c7,  with  its  branch 
e,  the  lower  end  of  which  opens  into  a  bottle  having  two  other 
openings.  Of  these,  one,  which  communicates  with  the  top  of 
the  bottle,  is  for  the  efflux  of  air;  the  other,  near  the  bottom, 
for  the  escape  of  water.  If  a  continuous  current  of  water  is 
caused  to  pass  through  d,  e  remaining  open,  it  carries  with  it  a 
quantity  of  air  which  passes  down  into  the  bottle;  and  if  the 
screw  clamp  c  is  so  adjusted  as  to  allow  the  water  to  flow  out 
of  the  bottle  at  the  same  rate  that  it  flows  in  from  <7,  the  water 
in  the  bottle  remains  at  the  same  level,  and  a  constant  stream 
of  air  escapes  from  b.  The  interruption  of  the  stream  of  air  so 
produced  is  effected  by  means  of  an  electro-magnet,  which  is  so 
arranged  that  each  time  the  voltaic  current  is  closed,  a  weight 
by  which  the  tube  is  compressed  is  lifted,  and  thus  air  is  in- 
jected so  long  as  the  magnet  is  in  action.  The  voltaic  current 
may  be  closed  aud  opened  either  by  a  metronome  or  by  the 
mercurial  breaker,  shown  in  fig.  223.  Two  copper  wires,  one 
of  which  is  connected  with  the  battery,  the  other  with  the  mag- 
net, run  along  the  top  of  the  wooden  bridge,  nearly  meeting  at 

1  A  somewhat  more  complicated  apparatus    (Waxxarluftpumpc   zur 
Erzeugunrj  conqiriiuirler  Lujfl)  is  sold  by  Desaga  of  Heidelberg. 


250  CIRCULATION   OF   THE    BLOOD. 

the  crown  of  the  arch  ;  here  the}-  descend  parallel  to  each  other, 
but  not  in  contact.  Below  the  arch  is  a  flat  vulcanite  bag,  on 
the  upper  surface  of  which  a  U  tube  is  supported  vertically, 
with  its  concavity  upwards.  The  ends  of  the  two  wires  are 
received  into  the  two  limbs  of  the  U-  As  the  bend  contains 
mercury,  it  is  obvious  that  whenever  the  bag  expands  the  cir- 
cuit is  closed,  and  broken  when  it  contracts.  The  rest  of  the 
mechanism  is  so  arranged  that  the  tube  is  closed  beyond  the 
breaker  whenever  the  magnet  is  not  acting,  and  open  so  long 
as  the  current  passes.  This  condition  can,  however,  never  be 
permanent;  for  after  an  interval  of  time,  which  can  be  very 
readily  regulated  by  altering  the  quantity  of  mercury  in  the  U 
tube,  the  bag  becomes  sufficiently  distended  to  close  the  cir- 
cuit. When  this  happens,  the  magnet  acts  and  opens  the  tube, 
allowing  the  distended  bag  to  discharge  itself.  This  contriv- 
ance answers  particularly  well  for  the  artificial  respiration  of 
rabbits.  The  needles  for  exciting  the  cord  are  constructed  in 
the  same  manner  as  those  described  in  the  preceding  paragraph  ; 
they  should,  however,  be  thicker  and  stronger. 

The  canulffl  having  been  placed  in  the  trachea  and  external 
jugular  vein,  and  the  apparatus  for  artificial  respiration  being 
in  order,  three-tenths  of  a  centimetre  of  a  one  percent,  solution 
of  curare  is  injected.  As  soon  as  respiration  ceases,  air  is  in- 
jected at  regular  intervals  by  the  metronome,  the  beats  of  which 
express  the  previous  frequency  of  breathing.  The  carotid 
artery  is  now  connected  with  the  kymograph,  and  the  animal 
placed  in  the  supine  position,  the  head-holder  being  so  arranged 
that  the  head  is  very  much  flexed  on  the  cervical  part  of  the 
spinal  column,  so  as  to  make  the  space  between  the  occipital 
bone  and  the  atlas  as  wide  as  possible.  In  doing  this,  great 
care  must  be  taken  not  to  strain  or  twist  the  artery,  or  kink  the 
air  tube.  This  done,  an  observation  must  be  made  of  the  arte- 
rial pressure,  and  the  atlanto-occipital  membrane  exposed  with 
as  much  dispatch  and  as  little  bleeding  as  practicable.  This 
is  best  effected  with  the  aid  of  the  notched  needle,  fig.  203/. 
With  the  help  of  this  needle,  three  ligatures  are  passed  under- 
neath the  muscles  which  stretch  vertically  on  either  side  of  the 
spine  of  the  atlas,  its  point  being  directed  towards  the  occipital 
spine  as  close  to  the  bone  as  possible.  It  is  usually  necessary 
to  pass  two  such  ligatures  in  line  on  either  side,  the  upper 
entering  where  the  lower  passes  out.  The  ligatures  having 
been  tightened  and  the  muscles  divided  in  the  middle  line,  it 
is  easy  to  expose  the  posterior  tubercle  of  the  atlas,  the  mem- 
brane, and  the  edge  of  the  occipital  bone,  without  hemorrhage. 

The  next  step  is  to  expose  the  cord  by  dividing  the  atlanto- 
occipital  membrane;  this  is  best  done  with  scissors  and  for- 
ceps. While  a  tracing  of  the  arterial  pressure  is  taken  by  an 
assistant,  the  cord  is  divided:  at  once  the  mercurial  column 


BY  DR.  BURDON-S ANDERSON.  251 

sinks  from,  say,  100  millimetres  to  20  or  30.  One  needle  is 
then  inserted  in  the  middle  line  above  the  posterior  tubercle 
of  the  atlas,  the  other  below  it,  the  key  being  closed.  On 
opening  the  latter  so  as  to  direct  the  induced  current  through 
the  needles,  the  arterial  pressure  rises  to  a  height  which  at 
first  equals,  if  not  exceeds,  that  at  which  it  stood  before  sec- 
tion. 

The  effects  of  exciting  the  cord  in  increasing  the  arterial 
pressure  are  seen  with  equal  distinctness  when  the  cord  is  not 
previously  divided.  In  both  cases  the  ascent  is  accompanied 
with  an  increase  of  the  frequency  of  the  contractions  of  the 
heart,  the  cause  of  which  will  be  investigated  in  a  future  sec- 
tion. 

Direct  Observation  of  the  Arteries  during  Excitation  of  the 
Cord. — That  the  increase  and  diminution  of  arterial  pressure 
observed  is  in  great  part,  if  not  entirety,  dependent  on  con- 
traction of  the  arterial  systems,  can  be  shown  in  several  ways. 
The  most  direct  consists  in  the  observation  of  the  arteries 
themselves.  In  the  rabbit,  the  arteria  sajrfiena,  which,  after 
leaving  the  femoral,  just  as  that  vessel  enters  the  adductor 
sheath,  takes  a  superficial  course  towards  the  inner  side  of  the 
knee,  may  be  observed  with  great  facility.  All  that  is  neces- 
sary is  to  divide  carefully,  first  the  skin,  and  then  the  fascia 
which  covers  it :  the  two  saphena  veins  which  lie  on  either 
side  of  it  serve  to  determine  its  exact  position.  In  this 
artery  it  can  be  readily  seen  that  as  the  pressure  rises  the 
vessel  contracts.  To  observe  the  effect  of  vascular  conti-ac- 
tion  on  the  heart,  that  organ  must  be  exposed.  In  a  curarized 
animal,  this  can  be  effected  without  interfering  materially  with 
the  vital  functions.  Ligatures  of  fine  copper  wire  having 
been  passed,  with  the  aid  of  a  curved  needle  (fig.  203,  e), 
around  the  3d,  4th,  5th,  and  6th  cartilages,  close  to  the  left 
edge  of  the  sternum,  and  a  second  vertical  series  of  ligatures 
around  the  corresponding  ribs  at  a  sufficient  distance  outwards, 
the  portion  of  the  thoracic  wall  which  lies  between  the  two 
series  can  be  removed  without  hemorrhage.  It  is  then  seen 
that  after  section  of  the  cord,  the  heart  is  flaccid  and  empty, 
and  that  its  cavities  fill  and  its  action  becomes  vigorous  when 
the  vascular  contraction  caused  by  excitation  of  the  peripheral 
end  forces  the  blood  forwards  so  as  to  fill  the  right  auricle. 

[For  the  experimental  proof  that  the  effects  of  excitation 
of  the  cord  above  described  are  not  dependent  on  the  increased 
vigor  of  the  contractions  of  the  heart,  see  §§  80,  81.] 

50.  (4.)  Section  of  the  Medulla  Oblongata  in  the 
Rabbit,  within  the  Cranium. — The  recent  experiments  of 
Ludwig  and  Owsjannikow  have  shown  that  the  medulla  m:iy 
be  divided  within  the  cranium  with  the  same  results  as  regards 
arterial  pressure  as  are  obtained  when  it  is  severed  immediately 


252  CIRCULATION    OF    THE    BLOOD. 

below  the  occipital  foramen.  For  this  purpose,  the  occipital 
bone  must  he  perforated  with  a  small  trephine  (fig.  203,  d)  in 
the  middle  line  between  the  occipital  protuberance  and  the 
occipital  spine  (see  fig.  224).  By  this  opening,  a  thin-bladed 
knife  is  introduced  in  the  middle  plane,  with  its  edge  outwards, 
by  which  the  medulla  is  divided,  first  on  one  side,  then  on  the 
other.  If  the  division  is  made  as  much  as  five  millimetres 
above  the  calamus  scriptorius,  the  diminution  of  arterial  press- 
ure produced  is  as  great  as  after  section  outside  of  the 
cranium.  In  experiments  in  which  the  division  was  made 
higher,  the  effect  was  found  to  be  lessened,  disappearing  when 
a  point  was  reached  about  a  millimetre  below  the  corpora 
quadrigemina. 

Experiments  relating  to  the  Refeex  Excitation  of  the  Vaso- 
motor Centre. 

The  vasomotor  centre,  although  constantly  in  activity,  may 
be  stimulated  by  impressions  received  by  it  through  afferent 
nerves.     This  can  be  shown  both  in  the  frog  and  in  mammalia. 

51.  Reflex  Excitation  of  the  Medulla  Oblongata  in 
the  Frog. — For  this  purpose,  the  nerves  in  question  may  be 
excited  either  with  the  aid  of  the  ordinary  excitor  (fig.  225), 
or  bj'  the  application  of  a  metallic  brush  to  the  skin.  In  the 
latter  case,  one  of  the  wires  which  form  the  secondary  circuit 
ends  in  a  point  which  is  inserted  into  the  muscles;  the  other, 
in  the  brush  which  is  kept  in  contact  with  the  skin  in  the  im- 
mediate neighborhood.  The  effect  should  be  observed  in  the 
web,  in  the  mesentery,  and  in  the  great  vessels  leading  to  the 
heart.  The  currents  employed  must  be  feeble  when  the  nerves 
are  excited  by  the  direct  application  of  the  electrodes  to  the 
sensory  nerves,  but  strong  when  it  is  intended  to  excite  their 
cutaneous  or  mucous  endings.  The  periods  of  excitation 
should  always  be  very  short.  The  experiment  may  be  varied 
as  follows:  a.  A  frog  having  been  carefully  curarized,  with 
the  same  precautions  as  were  recommended  for  studying  the 
effect  of  direct  excitation  of  the  medulla,  and  arranged  for  the 
microscopical  observation  of  the  circulation  in  the  web,  the 
points  of  the  excitor  are  placed  upon  the  tongue,  the  mouth 
being  kept  open  for  the  purpose.  On  opening  the  key,  the 
same  changes  exactly  are  observed  in  the  vessels  as  are  pro- 
duced by  direct  excitation.  At  the  first  moment  the  blood- 
stream in  the  arteries  is  accelerated,  but  immediately  after, 
the  arteries  begin  to  contract  sensibly.  The  contraction 
increases  gradually  but  rapidly  for  one  or  two  seconds,  and  is 
attended  with  slowing,  and  finally  witli  arrest,  of  the  circula- 
tion. A  maximum  of  narrowing  having  been  attained,  the 
effect  passes  off  as  it  came  on.      Even  if  the  excitation  is 


BY  DR.  BURDON-S ANDERSON.  253 

continued,  the  arteries  do  not  remain  contracted,  but  often 
exhibit  alternations  of  contraction  and  relaxation  at  irregular 
intervals.  For  observing  the  changes  of  rate  of  movement  in 
the  velocity  of  the  blood-stream,  the  veins  should  be  preferred ; 
for  in  them  the  initial  acceleration  is  not  quite  so  transitory  as 
in  the  arteries,  while  the  subsequent  slowing  is  as  distinct.  If 
it  is  desired  to  make  a  more  exact  observation,  the  method 
devised  by  Dr.  Riegel  must  be  used.  It  consists  in  comparing 
the  movements  of  the  blood  corpuscles  in  a  selected  artery  or 
vein,  with  that  of  a  current  of  water  containing  solid  particles 
in  suspension,  which  passes  through  a  horizontal  glass  tube 
fixed  in  the  eye-piece  of  the  microscope  at  such  a  distance  from 
the  eye-glass  as  to  be  distinctly  seen  by  the  observer.  One  end 
of  the  tube  communicates  with  a  large  bottle  placed  on  a  shelf 
at  a  higher  level  than  the  table,  containing  the  liquid  ;  the 
other,  with  the  discharge  tube  of  the  movable  warm  stage 
represented  in  fig.  3.  Ity  varying  the  height  of  the  dropper, 
the  rate  of  flow  through  the  eye-piece  can  be  readily  regulated. 
The  rate  of  flow  is  learnt  by  measuring  the  quantity  of  liquid 
discharged  per  second,  and  dividing  it  by  the  product  of  the 
lumen  of  the  glass  tube  and  the  magnifying  power  of  the 
microscope.  Thus,  if  the  rate  of  discharge  were  a  cubic  centi- 
metre in  15  seconds,  i.  e.,  6.6'  cubic  millimetres  per  second,  the 
lumen  of  the  tube  0.8  square  mill.,  and  the  magnifying  power 
300,  the  velocity  of  the  current  would  be  30Qy0.8=  0.02775  mill. 
The  determination  of  the  absolute  velocity  is  of  little  import- 
ance, the  object  being  rather  to  appreciate,  with  exactitude  and 
certainty,  the  changes  of  rate  which  occur  during  the  period 
of  observation,  b.  If,  instead  of  the  tongue,  the  surface  of 
the  skin  is  excited  with  the  brush,  the  appearances  observed 
are  very  similar.  The  initial  acceleration  of  the  blood-stream 
is  more  easily  observed  by  this  method  than  by  the  other,  c. 
Direct  Excitation  of  a  Sensory  Nerve. — A  frog  having  been 
curarized,  the  integument  is  divided  along  the  outer  and 
posterior  aspect  of  the  thigh  in  a  line  which  corresponds  in 
direction  with  the  slender  biceps  muscle,  or  leather  with  the 
groove  between  the  muscular  mass  which  covers  the  front  of 
the  femur  (triceps  femoris)  and  the  bulky  semi-membranosus. 
The  sciatic  nerve,  accompanied  by  the  sciatic  artery  and  vein, 
lies  immediately  underneath  the  biceps,  between  it  and  the 
semi-membranosus.  In  order  to  separate  it  from  the  vessels, 
it  is  best  to  bring  it  into  view  by  raising  the  biceps  on  a  blunt 
hook.  Both  webs  having  been  arranged  for  observation  under 
the  microscope,  the  nerve  is  divided  a  little  above  the  knee, 
and  the  central  end  laid  on  the  copper  points.  The  secondary 
coil  having  been  placed  at  a  considerable  distance  from  the 
primary,  and  the  eye  fixed  on  an  artery  of  the  web  of  the  un- 


254  CIRCULATION    OF    THE   BLOOD. 

injured  limb,  the  key  is  opened.  The  same  scries  of  phe- 
nomena present  themselves  as  before — contraction  and  slowing 
of  the  circulation,  preceded  by  a  much  less  obvious  accelera- 
tion. If  now  the  other  web  is  brought  under  the  microscope, 
it  is  seen  that  the  contraction  of  the  arteries  is  very  inconsider- 
able, the  acceleration  is  more  distinct.  The  explanation  of 
this  is  easy.  The  sciatic  nerve  being  the  channel  by  which 
most  of  the  vasomotor  fibres  find  their  way  to  the  arteries  of 
the  web,  those  vessels  are  in  great  measure  (but  not  entirely) 
paralyzed  by  its  division.  Consequentl}-,  of  the  three  effects 
produced  by  excitation  of  the  vasomotor  centre — viz.,  increased 
vigor  of  the  contractions  of  the  heart,  increase  of  arterial  press- 
ure, and  contraction  of  the  arteries — the  first  two  only  mani- 
fest themselves  in  acceleration  of  the  blood-stream.  In  the 
other  limb,  the  vasomotor  nerves  being  intact,  the  phenomena 
present  themselves  in  their  completeness.  The  effect  of 
direct  and  indirect  excitation  of  the  medulla  on  the  vessels  of 
the  mesentery  has  as  yet  been  imperfectly  investigated.  It  is 
certain  that  in  general  the  contraction  of  the  mesenteric 
arteries  is  much  less  marked  than  of  those  of  the  web.  It  is 
often  entirely  absent,  the  only  change  observed  during  excita- 
tion being  that  the  stream  is  accelerated.  These  facts  do  not 
indicate  that  these  arteries  are  out  of  the  control  of  the 
cerebro-spinal  centres,  but  merely  that  the  nerves  excited  are 
not  in  reflex  relation  with  them. 

52.  Reflex  Excitation  of  the  Medulla  Oblongata  in 
Mammalia. — The  vasomotor  centre  may  be  stimulated  in 
the  dog,  rabbit,  or  cat,  by  the  electrical  excitation  of  any  sen- 
sory nerve.  The  most  convenient  for  the  purpose  is  the  sciatic. 
The  requirements  are  the  same  as  for  an  ordinary  kymographic 
observation.  If  it  is  intended  to  excite  the  trunk  of  the  sciatic 
nerve,  the  animal  must  rest  on  its  side.  It  must  first  be  ren- 
dered insensible  by  opium  or  chloral,  and  subsequently  curar- 
ized.  In  order  to  expose  the  sciatic  nerve,  an  incision  must 
be  made  from  a  point  half  way  between  the  trochanter  and 
the  promontory  of  the  ischium  towards  the  tendon  of  the 
biceps.  Such  an  incision  runs  nearly  parallel  to  the  inner 
and  posterior  edge  of  the  long  head  of  the  muscle  just  named, 
which  edge  must  be  found  and  drawn  outwards.  In  the  upper 
third  of  the  thigh,  the  nerve  lies  between  the  biceps  and  the 
adductor  inagnus,  further  down,  between  the  biceps  and  the 
semi-membranosus.  If  it  is  desired  to  stimulate  the  nerve 
near  its  distribution,  the  peromeal  nerve  may  be  found  very 
readily  in  front  of  the  ankle,  on  the  fibular  side  of  the  com- 
mon extensor  of  the  toes.  It  is  often  called  the  n.  dorsalis 
pedis. 

Excitation  of  the  central  end  of  the  divided  sciatic  or  of  the 
peronoeal  nerve  produces  effects  which  are  indistinguishable  in 


BY    DR.    BURDON-SANDERSON.  255 

kind  from  those  of  direct  excitation  of  the  medulla,  although 
the  augmentation  of  arterial  pressure  and  other  concomitant 
phenomena  are  less  considerable.  In  the  case  of  the  doi'salis 
pedis,  however,  and  other  nerves  to  be  immediately  referred 
to,  there  is  a  marked  difference  between  the  condition  of  the 
arteries  in  the  region  to  which  the  excited  afferent  nerve  is 
distributed,  and  those  of  the  rest  of  the  body. 

Experiments  showing  that  the  same  Degree  of  Excitation 
op  a  Sensory  Nerve  wuicn  produces  General  Contraction 
op  the  Arteries  in  other  Parts  op  the  Body,  diminishes 
the  Tonus  of  the  Arteries  of  the  Part  to  which  the  Ex- 
cited Nerve  is  Distributed. 

53.  (1.)  Excitation  of  the  Nerves  of  the  External 
Ear  of  the  Rabbit. — The  ear  of  the  rabbit  derives  its  sensi- 
bility from  two  nerves,  both  of  considerable  size.  One  of 
these,  the  posterior  auricular,  approaches  the  surface  at  the 
back  of  the  neck,  very  near  the  middle  line,  and  runs  forwards 
and  outwards,  under  a  thin  covering  of  muscle,  to  the  root  of 
the  ear,  where  it  penetrates  a  process  of  cartilage,  easilj*  felt 
in  passing  the  finger  from  the  occiput  outwards.  By  making 
an  incision  between  this  process  and  the  occipital  spine,  the 
nerve  can  be  very  easily  found.  The  other  nerve  (n.  auricu- 
laris  maynus,  see  fig.  226)  springs  from  the  anterior  branches 
of  the  second  and  third  cervical  nerves  ;  it  becomes  superficial 
at  the  posterior  edge  of  the  sterno-mastoid,  and  then  runs  up- 
wards, covered  only  by  integument,  towards  the  thin  edge  of 
the  external  ear,  where  it  soon  divides  into  two  branches.  It 
is  most  easily  found  at  the  root  of  the  ear,  just  before  it  di- 
vides. 

The  animal  having  been  curarized,  the  apparatus  for  artificial 
respiration  is  connected  with  the  trachea,  and  the  manometer 
of  the  kymograph  with  the  carotid  artery.  The  great  auricu- 
lar nerve  is  then  carefully  exposed,  separated  from  the  sur- 
rounding parts  with  the  aid  of  two  pairs  of  blunt  forceps,  and 
divided.  The  next  step  is  to  arrange  the  lobe  of  the  ear  in 
such  a  way  that  the  central  artery  can  be  well  seen.  With 
this  view,  if  sunlight  is  not  at  command,  a  paraffin  lamp 
should  be  so  placed  that  its  light  may  be  thrown  on  the  ear 
from  behind  by  a  condensing  lens,  while  the  lobe  itself  is  sup- 
ported vertically  by  a  suitable  holder.  Before  beginning  the 
experiment,  the  central  artery  should  be  carefully  observed, 
attention  being  particularly  directed  to  the  rhythmical  changes 
of  diameter  which  it  undergoes.  Its  condition  having  been 
carefully  noted,  and  a  preliminary  kymographic  tracing  having 
been  taken,  for  the  purpose  of  preserving  a  record  of  the  pre- 
vious arterial  pressure,  the  central  end  of  the  nerve  is  laid 
upon  the  points  of  the  excitor,  and  the  key  opened  for  a  couple 


25$  CIRCULATION    OF    THE    BLOOD. 

of  seconds.  If  no  increase  of  arterial  pressure  takes  place,  the 
secondary  coil,  which  in  beginning  the  experiment  must  be 
distant  from  the  primary  one,  is  cautiously  brought  nearer  to 
it  until  this  effect  is  produced.  As  soon  as  this  is  the  case, 
it  is  usually  observed  that  the  artery  of  the  ear,  instead  of 
contracting,  dilates,  and  that  the  whole  lobe  obviously  con- 
tains more  blood  than  it  did  before.  Frequently,  however,  it 
happens  that,  notwithstanding  the  increase  of  arterial  press- 
ure, no  increased  vascular  injection  is  observable.  In  this 
case,  recourse  must  be  had  to  the  posterior  auricular  nerve, 
the  excitation  of  the  central  end  of  which  is  almost  certain  to 
be  followed  by  the  effect  in  question.  The  augmentation  of 
arterial  pressure  and  the  dilatation  of  the  auricular  artery 
appear  to  be  collateral  phenomena,  both  increasing  gradually 
during  the  few  seconds  which  succeed  the  commencement  of 
electrical  excitation.  If  care  is  taken  neither  to  prolong  the 
excitation  unduly  nor  to  use  too  strong  currents,  the  reaction 
may  be  witnessed  a  great  number  of  times  in  the  same  animal. 

54.  (2.)  Excitation  of  the  Dorsalis  Pedis. — When  the 
central  end  of  the  divided  dorsal  nerve  of  the  foot  is  excited, 
phenomena  occur  of  a  similar  nature.  To  enable  the  observer 
to  judge  of  the  effect,  the  saphenous  artery  must  be  exposed 
in  its  course  down  the  inner  side  of  the  lower  half  of  the  thigh, 
as  recommended  in  §  49.  It  is  then  seen  that  during  and 
after  excitation  of  the  central  end  of  the  divided  nerve,  the 
artery  gradually  dilates,  subsequently  regaining  its  former 
dimensions. 

The  general  result  of  the  preceding  experiments  may  be 
expressed  b}'  sa}'ing  that  the  afferent  nerves  to  which  the}r 
relate  (in  common  probably  with  other  sensoiy  nerves)  con- 
tain fibres  so  endowed  that,  when  they  are  excited,  the  action 
of  the  vasomotor  centre  is  inhibited  or  suspended,  as  regards 
certain  regions  with  which  the  nerves  in  question  are  in  close 
anatomical  relation.  In  its  relations  to  the  vasomotor  ner- 
vous system,  the  words  "  inhibitory"  and  "depressor,"  both 
of  which  are  used  bj-  physiologists  to  denote  the  case  in  which 
arterial  tonus  is  diminished  by  excitation  of  an  afferent  nerve, 
may  be  regarded  as  equivalent. 


Experiments  relating  to  the  effects  of  direct  Excitation 
and  Division  of  the  Vasomotor  Nerves. 

When  a  vasomotor  nerve  is  excited  directly,  the  arteries  of 
the  region  to  which  it  is  distributed  contract.  When  it  is 
divided,  they  become  permanently  larger,  and  remain  unaffect- 
ed bj'  changes  in  the  condition  of'  the  vasomotor  centre, 
whether  these  are  determined  by  direct  or  reflex  excitation. 


BY    DR.    BURDON-SANDERSON.  257 

55.  (1.)  Demonstration  of  the  Vasomotor  Functions 
of  the  Cervical  Portion  of  the  Sympathetic  Nervous 
System  in  the  Rabbit. — In  1852,  Brown-Sequard  showed 
that  when  the  sympathetic  nerve  is  divided  in  the  neck,  the 
central  artery  of  the  ear  dilates,  and  the  organ  becomes  vascu- 
lar ;  and  that  when  the  peripheral  end  is  excited,  the  same  ar- 
teries contract ;  and  in  the  same  year  he  demonstrated  that 
the  former  effect  was  dependent  on  paralysis,  the  latter  on 
spasm  of  the  muscular  walls  of  the  vessels. 

A  rabbit  having  been  placed  on  the  support  in  the  prone 
position,  about  four  cubic  centimetres  of  a  five  per  cent,  solu- 
tion of  chloral  (obtained  by  diluting  a  stronger  solution  with 
the  required  proportion  of  the  ordinary  solution  of  chloride  of 
sodium)  is  gradually  injected  into  the  crural  vein.  [For  the 
method  of  exposing  the  crural  vein  and  of  inserting  the  canula, 
see  §  49].  As  soon  as  the  animal  is  insensible,  an  incision  is 
made  about  two  inches  in  length  parallel  with  the  trachea;  so 
as  to  expose  the  edge  of  the  sterno-mastoid  muscle  on  one 
side.  The  carotid  artery  is  then  brought  into  view,  separated 
from  the  vagus,  and  drawn  forward  from  beneath  the  edges  of 
the  muscle  with  the  (fig.  203,  c)  hook,  when  it  is  seen  that  two 
small  nerves,  both  much  smaller  than  the  vagus,  are  drawn 
forward  with  it,  embedded  in  the  membranous  sheath  (fig. 
227).  Of  these  two  nerves,  one,  which  is  the  smaller  of  the 
two,  is  the  depressor — an  important  cardiac  branch  of  the 
vagus;  the  other  is  the  s3-mpathetic.  To  discriminate  between 
them,  all  that  is  necessary  is  to  trace  them  both  upwards.  It 
is  then  seen  that  the  depressor  arises  by  one  root  from  the 
vagus  trunk,  by  another  from  the  superior  laryngeal;  whereas 
the  sympathetic  continues  its  course  upwards  alongside  of  the 
artery.  The  sympathetic  is  also  distinguishable  by  its  gray 
color.  A  loose  ligature  having  been  placed  round  the  nerve, 
the  condition  of  the  posterior  auricular  artery  should  be  care- 
fully observed,  and  noted  in  the  manner  recommended  in  the 
previous  paragraph.  On  dividing  the  nerve,  it  is  seen  that 
the  artery  dilates,  the  rhythmical  movements  cease,  and  the 
whole  vascular  network  of  the  ear  rapidly  becomes  injected 
with  blood.  The  change  in  the  condition  of  the  organ  is  very 
similar,  both  in  degree  and  in  kind,  to  that  observed  after  ex- 
citation of  the  central  end  of  the  auricular  nerve,  but  differs 
from  it  in  being  more  permanent.  If  after  a  few  minutes  the 
ears  are  held,  one  in  each  hand,  it  is  felt  that  that  of  the  in- 
jured side  is  warmer  than  the  other.  If  now  the  peripheral 
end  of  the  divided  nerve  is  placed  between  the  copper  points 
and  the  key  opened,  the  artery  contracts  and  the  congestion 
of  the  car  disappears. 

This  experiment  shows  conclusively  that  most  of  the  spinal 
vasomotor  nerves  which  are  distributed  to  the  arteries  of  the 
17 


258  CIRCULATION   OF   TIIE    BLOOD. 

integument  of  the  head,  must  reach  their  destination  by  pass- 
ing through  the  superior  cervical  ganglion.  As,  however,  the 
superior  ganglion  is  also  in  direct  communication  with  the 
spinal  cord,  the  vascular  paralysis  is  incomplete  unless  this 
communication  is  broken  by  the  extirpation  of  the  ganglion. 
To  accomplish  this,  the  incision  must  be  continued  upwards 
in  the  angle  of  the  jaw  (see  fig.  227).  The  carotid  artery  and 
the  vagus  which  accompanies  it,  having  been  brought  into 
view  as  far  upwards  as  the  stylohyoid  muscle,  are  drawn  for- 
wards and  towards  the  middle  line  with  the  blunt  hook  by  an 
assistant,  while  the  sympathetic  trunk  is  followed  upwards 
behind  the  artery  with  the  aid  of  two  pairs  of  blunt  forceps. 
The  space  in  which  the  ganglion  lies  is  crossed  by  the  trunk 
of  the  hypoglossal  nerve,  and  by  the  st3'lohyoid  muscle.  The 
latter  should  be  divided.  The  extirpation  of  the  ganglion  is 
best  effected  with  blunt-pointed  scissors.  After  section  of  the 
sympathetic  trunk  in  the  neck,  the  normal  condition  of  the  ear 
is  gradually  restored ;  but  if  the  ganglion  is  destroyed,  the 
effect  is  permanent. 

56.  (2.)  Demonstration  of  the  Vasomotor  Functions 
of  the  Splanchnic  Nerves. — The  splanchnic  nerves  con- 
tain (in  addition  to  those  fibres  which  govern  the  peristaltic 
movements  of  the  intestine,  with  which  we  have  at  present  no 
concern)  sensory  and  vasomotor  fibres.  The  vasomotor  fibres 
are  distributed  to  the  arteries  of  the  abdominal  viscera.  Their 
importance  depends  on  the  fact  that  these  arteries  receive  so 
large  a  share  of  the  systemic  blood-stream  (especially  in  the 
rabbit),  that  the  resistance  offered  by  the  arterial  system  to 
the  discharge  of  blood  from  the  heart  is  largely  affected  by 
any  alteration  of  their  calibre.  The  sensory  part  of  the  nerve, 
in  common  with  other  sensory  nerves,  contains  fibres  by  which 
the  vasomotor  centre  is  influenced.  It  is  also,  as  will  be  seen 
in  a  future  section,  in  reflex  relation  with  the  heart  through 
the  vagus.  The  splanchnic  nerve  in  the  rabbit  leaves  the  sympa- 
thetic trunk  at  the  8th  or  9th  ganglion,  passes  downwards  in 
front  of  the  psoas  major  muscle,  receiving  branches  from  the 
other  thoracic  ganglia.  At  the  level  of  the  tenth  thoracic 
vertebra,  the  two  nerves  lie  on  either  side  of  the  descending 
aorta,  and  accompany  it  downwards  until  it  reaches  the  dia- 
phragm, at  which  point  the  right  splanchnic  is  further  away 
from  the  vessel  than  the  left.  After  entering  the  belly,  the 
left  splanchnic  retains  the  same  relation  to  the  aorta  as  before, 
ending  in  the  lower  of  the  two  caeliac  ganglia,  which  is  easily 
found  above  the  left  supra-renal  capsule  on  the  front  of  the 
aorta.  The  right  nerve  is  more  difficult  to  find  from  its  lying 
further  from  the  aorta,  separated  from  it  by  the  breadth  of  the 
vena  cava.  It  ends  at  the  level  of  the  right  supra-renal  cap- 
sule, in  the  superior  caeliac  ganglion  which  lies  in  front  of  the 


BY   DR.    BURDON-SANDERSON.  259 

vein.  The  splanchnic  nerve  may  be  reached  either  in  the  ab- 
domen or  in  the  thorax.  In  very  exact  experiments,  and  es- 
pecially in  those  that  relate  to  the  functions  of  the  afferent 
fibres,  it  is  obviously  desirable  that  these  organs  should  not 
be  exposed  b}r  opening  the  peritonoeal  cavity;  but  for  the  pur- 
pose of  demonstrating  the  vasomotor  functions  of  the  nerve, 
this  precaution  is  unnecessary.  When  one  of  the  splanchnic 
nerves  is  divided  in  the  rabbit,  the  arterial  pressure  sinks ;  on 
electrical  excitation  of  the  divided  nerve,  it  rises  to  a  height 
which  far  exceeds  the  normal  limits.  Section  of  the  other 
nerve  is  followed  by  further  reduction,  which,  however,  is  not 
so  considerable  as  that  produced  by  division  of  the  first.  The 
reduction  of  pressure  after  section  is  attended  with  increase, 
the  elevation  of  pressure  after  excitation  with  decrease  of  the 
frequency  of  the  pulse.  These  facts  are  demonstrated  as  fol- 
lows : — 

A  chloralized  rabbit  having  been  secured  in  the  prone 
position,  and  one  carotid  connected  with  the  kymograph,  the 
abdominal  cavity  is  freely  opened  in  the  linea  alba.  The  in- 
tegument is  then  carefully  divided  by  a  transverse  incision, 
which  extends  outwards  from  the  first  incision  a  little  below 
the  edge  of  the  ribs.  A  curved  needle,  of  the  form  shown  in 
fig.  203  e,  guarded  by  the  left  forefinger,  is  then  passed  under 
the  abdominal  wall  in  the  direction  of  the  incision.  Its  point 
having  been  brought  out  about  two  and  a  half  inches  from  the 
linea  alba,  the  ligatures  are  tightened  in  such  a  way  that  the 
muscles  are  constricted  at  different  levels.  The  part  between 
the  ligatures  is  then  divided  by  a  horizontal  incision,  which 
may  be  continued  in  the  same  direction  without  hemorrhage. 
This  done,  the  left  splanchnic  nerve  is  plainly  seen  running 
down  parallel  to  the  aorta  on  its  left  side,  towards  the  supra- 
renal capsule.  The  space  in  which  it  lies  is  occupied  by  very 
loose  cellular  tissue  covered  by  peritoneum,  which  must  be 
broken  through  to  get  at  the  nerve. 

Immediately  after  the  abdominal  cavity  is  opened — that  is, 
before  the  nerves  are  touched — there  is  a  very  considerable 
rise  of  arterial  pressure,  which  is  accompanied  with  slowing 
of  the  pulse.  These  effects  are,  however,  only  transitory,  the 
mercurial  column  sometimes  sinking  immediately  afterwards 
below  its  original  level.  After  division  of  the  left  splanchnic 
it  sinks  very  considerably,  often  as  much  as  forty  millimetres 
(i.e.,  more  than  an  inch  and  a  half ).  On  placing  the  peri- 
pheral cut  end  between  the  copper  points  of  the  excitor  and 
opening  the  key,  the  column  suddenly  rises.  The  sinking  pro- 
duced by  section  of  the  right  nerve  is  comparatively  incon- 
siderable. As  it  is  very  difficult  to  get  at,  its  division  may  be 
omitted,  all  that  is  essential  in  the  experiment  being  observ- 
able after  section  of  the  left. 


260  CIRCULATION    OF   THE    BLOOD. 

The  following  numerical  results  are  derived  from  one  of 
Lndwig  and  Cyon's  experiments:  Previous  arterial  pressure, 
90  millimetres;  after  division  of  left  splanchnic,  41  mill.; 
during  excitation  of  peripheral  end  of  divided  nerve,  115  mill.; 
after  division  of  right  splanchnic,  31  mill.  After  section  of 
both  nerves,  the  vessels  of  all  the  abdominal  viscera  are  seen 
to  be  dilated.  The  portal  system  is  filled  with  blood ;  the 
small  vessels  of  the  mesentery,  and  those  which  ramify  on  the 
surface  of  the  intestine  are  beautifully  injected,  the  vessels  of 
the  kidneys  are  dilated,  and  the  parenchyma  is  hyperoemic;  all 
of  which  facts  indicate,  not  merely  that  by  the  relaxation  of 
the  abdominal  bloodvessels  a  large  proportion  of  the  resist- 
ance to  the  heart  is  annulled,  but  that  a  quantity  of  blood  is, 
so  to  speak,  transferred  into  the  portal  system,  anil  thereby  as 
completely  discharged  from  the  systemic  circulation  as  if  a 
great  internal  hemorrhage  had  taken  place. 


Part  II. — The  Heart. 

Section  V.— The  Movements  of  the  Heart. 

The  method  of  demonstrating  the  movements  of  the  heart, 
stated  in  the  order  of  their  importance,  are  the  following:  1. 
Exposure  of  the  contracting  heart  in  situ.  2.  Application  of 
instruments  to  the  prsecordla,  for  the  purpose  of  measuring  the 
cardiac  movements  of  the  wall  of  the  chest.  3.  Listening  to 
the  sounds  of  the  heart.  4.  Imitating  the  movements  of  the 
living  heart  by  the  production  of  similar  passive  movements 
in  the  dead  heart. 

57.  Study  of  the  Movements  of  the  Heart  in  the 
Frog. — Before  beginning  the  study  of  its  movements,  an  ade- 
quate knowledge  of  the  form  and  anatomical  relations  of  the 
organ  must  be  gained  by  dissection.  For  this  purpose,  the 
heart  and  great  vessels  should  be  filled  with  some  solid  sub- 
stance which  can  be  rendered  fluid  by  warming  it;  such,  for 
example,  as  cacao  butter  or  the  ordinary  gelatin  mass  (see 
Chap.  VI.).  This  must  be  injected  by  the  vena  cava  inferior 
in  sufficient  quantity  to  fill  the  heart  and  great  vessels  (see 
fig.  228).  It  is  then  seen  that  the  organ,  as  a  whole,  is  egg- 
shaped  ;  but  is  more  or  less  flattened  from  side  to  side  by  a 
furrow  which  crosses  the  heart  nearly  at  right  angles  to  its 
axis,  but  inclines  downwards  towards  the  left;  it  is  divided 
into  an  upper  globular  (formed  of  the  two  auricles)  and  a 
lower  conical  part  (the  ventricle).  On  its  anterior  aspect,  the 
ventricle  is  continuous  with  a  cylindrical  prominence  (the 
bulb),  which  projects  from  the  anterior  aspect  of  the  right 
auricle,  and  terminates  above  by  dividing  into  two  arteries,  the 


BY    DR.    BURDON-SANDERSON.  261 

right  and  left  aorta.  Of  these  aortfe,  which  part  from  eacli 
other  at  the  middle  line,  the  left  is  the  larger.  The  posterior 
wall  of  the  right  auricle  extends  backwards  into  a  club-shaped 
appendage,  the  sinus  venosus.  This  body  may  be  described 
as  the  dilated  end  of  the  large  vena  cava  inferior.  It  first 
extends  vertically  upwards  in  the  middle  line,  in  continuity 
with  that  vein,  applying  itself  against  the  oesophagus  behind, 
and  opening  towards  the  front  into  the  right  auricle,  from 
which  it  is  separated  by  a  slight  furrow.  At  the  top  it  re- 
ceives on  either  side  the  two  venae  cavae  superiores,  which, 
however,  are  relatively  small.  The  two  auricles  are  separated 
from  each  other  b}'  a  septum,  which  stretches  as  a  curtain  from 
before  backwards,  between  them.  This  curtain  ends  below  in 
a  crescentic  margin,  beneath  which  the  two  cavities  communi- 
cate freely.  The  orifice  leading  from  the  sinus  venosus  into 
the  right  auricle  is  guarded  by  a  well-marked  Eustachian  valve, 
which  hangs  downwards  and  towards  the  right.  The  auriculo- 
ventricular  valve  consists  of  an  anterior  and  a  posterior  cur- 
tain, both  of  which  are  continuous  at  their  edges  with  the 
auricular  septum. 

The  mode  of  exposing  the  heart  has  already  been  described. 
The  facts  to  be  observed  when  the  pericardium  is  opened  are 
the  following :  The  series  of  muscular  movements  which  are 
performed  b}'  the  heart  each  time  it  contracts  is  seen  to  begin 
at  the  upper  end  of  the  vena  cava  inferior  and  sinus  venosus. 
From  the  sinus  the  peristaltic  wave  extends  to  the  auricles; 
but  it  is  not  until  the  auricular  contraction  is  complete  that 
the  ventricle  suddenly  draws  itself  together.  Before  this  last 
act  is  accomplished,  it  is  asually  seen  that  the  sinus  venosus 
is  fall,  and  the  auricles  are  already  filling.  In  a  moment  they 
become  distended  and  contract,  transferring  the  blood  they 
contain  to  the  now  empty  and  flaccid  ventricle,  which  in  its 
turn  forwards  it  onwards  to  the  bulbus  aortas  and  arterial 
system.  In  consequence  of  the  fact  that  during  the  contrac- 
tion of  the  ventricle  the  auricles  are  already  filling  with  blood, 
and  that  the  ventricle  does  not  fill  until  the  auricle  contracts, 
the  successive  appearances  presented  by  the  heart  during  each 
cardiac  period  are  very  much  as  if  there  were  a  constant  ex- 
change of  blood  between  the  two  great  chambers  into  which 
the  organ  is  divided,  and  at  once  suggest  the  notion  that  the 
auricles  and  ventricle  dilate  and  contract  alternate^',  the  one 
seeming  to  contract  while  the  other  dilates,  and  vice  versa. 
It  is  easy,  however,  for  any  one  who  possesses  the  faculty  of 
observation  to  satisfy  himself  that  this  is  not  the  case,  and 
that,  while  the  ventricular  contraction  is  determined  by  the 
auricular,  and  the  auricular  by  that  of  the  sinus,  the  last 
originates  of  itself — i.  e.,  independently  of  any  previous 
movement. 


262  CIRCULATION    OF   THE    BLOOD. 

The  precise  time  between  the  successive  acts  above  described 

may  be  measured  by  arranging  a  lever  of  the  second  order  in 
such  a  way  that,  while  it  rests  near  its  bearings  on  the  con- 
tracting heart,  and  follows  its  movements,  its  distal  end  in- 
scribes those  movements  on  the  cylinder  of  the  recording  ap- 
paratus. In  this  way  a  tracing  is  obtained  (Fig.  220),  in 
which  the  relaxation  of  the  heart  is  marked  by  a  rapid  descent 
of  the  lever,  the  auricular  contraction  by  a  first  ascent,  the 
commencement  of  that  of  the  ventricle  by  a  second,  and  its 
continuance  by  a  slow  subsidence,  suddenly  ending  in  the 
rapid  diastolic  descent  already  mentioned.  Thus,  in  the  ex- 
ample given,  the  interval  between  the  vertical  lines  a  and  b  cor- 
responds to  the  auricular  s}'stole  ;  that  between  b  and  c  to  the 
contraction  of  the  ventricle — so  that  the  auricles  are  in  dia- 
stole from  b  to  a,  the  ventricles  from  c  to  b. 

58.  Study  of  the  Movements  of  the  Heart  in  Mam- 
malia.— For  this  purpose  a  rabbit  must  be  completely  chlo- 
ralized.  The  trachea  having  been  connected  with  the  appa- 
ratus for  artificial  respiration,  and  the  frequency  and  quantity 
of  the  inflations  carefully  regulated,  the  chest  is  opened  in  the 
manner  already  indicated  in  §  49.  The  facts  to  be  studied  are 
the  following  :  a.  At  the  beginning  of  the  period  of  relaxation, 
the  heart  is  so  flaccid  that  it  obeys  the  law  of  gravitation,  and 
is  consequently  flattened  from  side  to  side,  just  as  we  usually 
see  it  in  the  dead  body.  It  does  not  follow,  from  this  observa- 
tion, that  the  relaxed  heart  has  the  same  form  when  inclosed 
in  the  thorax,  but  on  other  grounds  it  probably  is  so,  for  its 
form  within  the  chest  when  in  the  flaccid  condition  is  mani- 
festly determined  partly  by  gravity,  partly  by  the  shape  of  the 
space  in  which  it  is  contained;  and  inasmuch  as  the  space  is 
a  wedge-shaped  one,  bounded  anteriorly  b}'  the  sternum  and 
ribs,  posteriorly  by  the  diaphragm,  but  virtually  unlimited 
towards  either  side,  we  may  be  quite  sure  that  the  organ  is  at 
least  as  much  flattened  antero-posteriorly  in  the  natural  state, 
as  it  is  seen  to  be  when  the  chest  is  open.  b.  During  the  re- 
mainder of  the  diastole  the  ventricles  are  still  flaccid  and  per- 
fectly passive,  but  the  conditions  are  changed.  While  gradu- 
ally filling  with  blood,  they  go  through  those  changes  of  form 
which  are  exhibited  by  a  bladder  contained  in  a  basin  when  it 
is  gradually  filled  with  water,  c.  At  the  end  of  diastole  fol- 
lows a  very  short  period,  during  which,  although  the  ventricles 
are  still  soft,  active  muscular  movements  can  be  observed. 
This  is  known  as  the  prse-systolic  period.  Systole  has  in  re- 
ality begun;  but  the  auriculo-ventricular  valves  not  having 
yet  had  time  to  close,  the  ventricular  contraction  is  unresisted. 
The  heart,  like  any  other  muscle,  so  long  as  it  contracts  with- 
out opposition,  is  soft.  cl.  The  moment  that  the  valves  close, 
the  heart  hardens   and  becomes   globular,   slightly   twisting 


BY    DR.    BURDON-SANDERSON.  263 

round  its  axis,  -while  the  apex  is  thrown  forward,  and  at  the 
same  time  approaches  the  base.  If  at  the  moment  of  ventri- 
cular hardening  the  attention  is  fixed  on  the  aorta,  that  great 
artery  is  seen  to  undergo  the  same  changes  of  form  which  we 
have  already  studied  in  the  arterial  pulse — changes  due  partly 
to  lateral  expansion,  i.  e.,  increase  of  diameter ;  partly  to  axial 
expansion,  i.  e.,  increase  of  length.  The  "locomotive"  move- 
ment, which  results  from  the  axial  expansion  of  the  aorta,  has 
its  influence  on  the  heart,  for  it  compensates  for  the  axial 
shortening  which  occurs  when  the  heart  gathers  itself  up  into 
a  globe  to  overcome  the  arterial  resistance  which  is  opposed 
to  it  at  the  moment  that  it  begins  to  force  its  contents  into 
the  already  distended  arteries. 

In  the  preceding  paragraphs  the  attention  of  the  student  has 
been  directed  entirely  to  the  arterial  side  of  the  heart,  i.  e.,  to 
the  movements  of  the  ventricles  and  great  arterial  trunks. 
These  having  been  mastered,  he  must  next  observe  those  of 
the  auricles,  with  special  reference  to  the  order  of  time  in 
which  they  occur. 

At  the  commencement  of  the  period  of  ventricular  relaxa- 
tion the  whole  heart  is  flaccid.  The  duration  of  this  period 
varies  inversely  as  the  frequenc}7  of  the  pulse,  so  that  no 
general  statement  can  be  made  with  respect  to  it.  As  long 
as  it  lasts,  blood  enters  the  auricles  from  the  systemic  and 
pulmonaiy  veins.  At  a  moment  which  anticipates  the  harden- 
ing of  the  ventricles  (in  the  rabbit)  by  something  like  a  fifth 
of  a  second,  the  auricles  harden,  while  the  ventricles,  which 
have  alread}'  received  a  certain  quantity  of  blood  through  the 
open  auriculo-ventricular  orifices,  fill  much  more  rapidly. 
This  hardening  of  the  auricles  is  not,  however,  to  be  compared 
either  in  vigor  or  suddenness  to  that  of  the  ventricles  ;  it 
docs  not  affect  the  whole  auricle  at  once,  but  rather  seems  to 
spread  from  the  vena?  cava?  towards  the  ventricles  as  a  wave 
of  contraction.  While  the  auricle  is  still  contracting,  the  pre- 
paratory "  prae-s}Tstolic"  movements  begin  in  the  ventricles, 
culminating,  as  already  described,  in  the  ventricular  shock,  or 
heart  pulse. 

To  complete  the  stud}r  of  the  movements  of  the  heart  in 
situ,  they  should  be  observed  under  various  abnormal  condi- 
tions, e.  g.,  under  the  influence  of  section  and  excitation  of 
the  vagi,  in  dyspnoea,  and  after  hemorrhage.  The  appear- 
ances then  seen  will  be  referred  to  under  the  proper  heads. 

59.  The  Cardiac  Impulse. — It  has  been  already  stated 
that  the  ventricular  part  of  the  heart  is  contained,  both  in 
man  and  in  the  lower  mammalia,  in  a  somewhat  wedge-shaped 
ipace,  the  posterior  wrall  of  which  formed  by  the  diaphragm  is 
more  or  less  resistant.  Consequently,  when  the  ventricles 
suddenly  harden  and  become  globular,  they  knock  against  the 


2G4  CIRCULATION    OF    THE    BLOOD. 

wall  of  the  chest  with  more  or  less  violence.  This  knock  is 
called  the  cardiac  impulse.  It  is  precisely  coincident  with  the 
complete  closure  of  the  auriculo- ventricular  valves,  and  deter- 
mines the  bursting  open  of  the  sigmoid  valves.  If  the  base 
of  the  heart,  ?'.  e.,  the  roots  of  the  great  arteries,  were  fixed, 
the  shortening  of  the  ventricular  axis,  which,  as  we  have  seen, 
occurs  at  the  moment  of  hardening,  would  determine  a  with- 
drawal or  retraction  of  the  apex  from  the  position  occupied 
by  it  in  diastole.  As,  however,  this  shortening  is  attended 
with  lengthening  of  the  aorta,  its  retractive  effect  is  more  or 
less  neutralized,  so  that  the  seat  of  impulse — in  other  words, 
the  centre  towards  which  the  muscular  mass  of  the  ventricles 
draws  itself  together — is  not  far  from  the  position  occupied 
by  the  apex  of  the  heart  when  in  a  state  of  relaxation.  This 
can  be  demonstrated  both  in  man  and  in  the  lower  animals. 
In  a  rabbit  or  dog  rendered  insensible  by  opium  or  chloral,  a 
number  of  long  slender  needles  are  introduced  into  the  heart 
in  the  following  positions:  No.  1  is  inserted  vertically  into 
the  ventricle  at  the  point  at  which  its  knock  can  be  felt  by 
the  finger  most  distinctly.  From  this  point  a  line  is  drawn 
upwards  and  inwards  towards  the  root  of  the  aorta,  along 
which  Nos.  2,  3,  and  4  are  inserted  in  a  similar  manner  in  the 
intercostal  spaces.  In  like  manner,  Nos.  5  and  G  are  inserted 
at  equal  distances  on  either  side  of  the  impulse  in  the  same 
intercostal  space.  The  movements  executed  by  these  several 
needles  differ  according  to  their  relation  to  the  central  one, 
No.  1,  which,  although  it  is  affected  by  the  ascent  and  descent 
of  the  diaphragm,  is  indifferent  as  regards  the  heart.  Of  the 
series,  Nos.  2,  3,  and  4,  the  free  end  of  each  performs  an  in- 
stantaneous upward  movement,  the  extent  of  which  is  in  pror 
portion  to  its  distance  from  No.  1 ;  and  finalljr,  Nos.  5  and  6 
oscillate  more  or  less  horizontally,  their  free  ends  receding 
from  each  other,  as  well  as  from  No.  1,  at  the  moment  of  the 
impulse.  From  these  facts  we  learn  that,  whereas  that  part 
of  the  ventricular  mass  which  knocks  against  the  chest  is 
nearly  stationary,  the  base  of  the  heart  moves  downwards, 
and  to  the  left  at  the  moment  of  the  ventricular  hardening, 
i.  e.,  of  the  aortic  pulse;  and  that  the  other  parts  of  the  ven- 
tricles are  drawn  towards  the  impulse  in  a  degree  proportional 
to  their  distance  from  it. 

In  man,  the  same  facts  are  demonstrated  with  the  aid  of  the 
cardiograph.  The  word  cardiograph  has  been  applied  by 
various  writers  to  a  variety  of  instruments,  which  differ  from 
each  other  both  in  their  form  and  in  the  principles  on  which 
they  are  constructed,  but  agree  in  the  purpose  which  they  are 
intended  to  fulfil.  This  purpose  is  the  recording  of  the  cardiac 
movements  of  the  wall  of  the  chest  by  the  graphic  method. 


BY    DR.    BURDON-SANDERSON.  265 

60.  The  Cardiograph. — The  cardiograph  I  use  is  shown 
in  fig.  230.  Its' most  important  part  is  a  hollow  disk,  the  rim 
and  back  of  which  are  of  brass ;  the  front  is  of  thin  India- 
rubber  membrane.  This  disk  is  called  a  tympanum.  To  the 
brass  back  a  flat  steel  spring  is  screwed,  which  is  bent  twice  at 
right  angles  in  the  same  direction,  in  such  a  way  that  it  over- 
hangs the  India-rubber  membrane.  The  extremity  of  this 
spring,  which  is  exactly  opposite  the  centre  of  the  face  of  the 
tympanum,  is  perforated  by  a  steel  screw,  the  point  of  which 
rests  on  the  membrane,  while  its  head  is  surmounted  by  an 
ivory  knob.  The  tympanum  is  further  provided  witli  three 
adjusting  screws,  by  which,  when  in  use,  it  rests  on  the  wall 
of  the  chest,  with  its  face  parallel  to  the  surface,  and  can  be 
approximated  or  withdrawn  at  will.  It  is  evident  that  when 
the  screws  are  so  adjusted  that  the  spring  presses  on  the  chest, 
whatever  movements  of  expansion  or  retraction  are  made  by 
the  surface  to  which  it  is  applied  are  communicated  to  it,  and 
by  it  to  the  India-rubber  membrane  with  which  its  point  is  in 
contact.  The  cavity  of  the  disk  communicates  by  a  vulcanized 
India-rubber  tube  with  a  second  tympanum,  represented  in  fig. 
231,  in  such  a  way  that  the  two  tympana  and  the  tube  inclose 
an  air-tight  cavity.  The  result  of  this  arrangement  is,  that 
whatever  movement  is  performed  by  the  first  is  simultaneously 
reproduced,  but  in  the  reverse  direction,  by  the  second.  If 
the  tympana  are  of  equal  area,  the  extents  of  the  primary  and 
secondary  movements  are  equal.  When,  as  is  usually  the 
case,  the  areas  are  unequal,  the  extent  of  movement  is  approxi- 
mate^- inversely  proportional  to  the  areas.  The  movement  of 
the  second  tympanum  is  magnified  and  inscribed  on  the  regis- 
tering cylinder  by  a  lever  in  the  manner  explained  in  a  pre- 
vious paragraph.  By  this  apparatus  a  tracing  is  obtained, 
which  is  an  exact  representation  of  the  movements  of  the  sur- 
face against  which  the  spring  is  applied,  so  that,  if  the  instru- 
ment is  graduated,  it  may  be  used  not  only  for  the  purpose  of 
estimating  the  relative  duration  of  those  movements,  but  for 
measuring  their  extent. 

For  the  purpose  of  studying  the  cardiac  impulse  in  the  hu- 
man chest,  the  subject  should  be  allowed  to  rest  supine  on  a 
flat  surface,  with  his  head  on  a  pillow.  The  impulse  is  sought 
for  in  the  normal  position,  i.e.,  in  the  space  between  the  fifth 
and  sixth  ribs,  about  half  an  inch  nearer  the  sternum  than  the 
mammary  line  (the  line  which  passes  vertically  through  the 
nipple).  On  applying  the  cardiograph  in  this  position,  with 
the  ivory  knob  pressing  against  the  seat  of  impulse,  a  tracing 
is  always  obtained  which  has  the  general  characters  exhibited 
in  Fig.  232a,  in  which  the  moment  of  hardening  is  indicated 
by  a  sudden  ascent  of  the  lever,  and  the  end  of  the  ventricular 
systole  by  an  equally  marked,  but  not  so  sudden,  descent.    If 


266  CIRCULATION   OF   THE    BLOOD. 

now  the  cardiograph  is  shifted  towards  the  sternum,  the 
character  of  the  tracing  is  entirely  altered.  '(See  Fig.  2326). 
The  ventricular  hardening  is  still,  indeed,  indicated  by  a  jerk 
upwards  of  the  lever;  but  this  is  immediately  succeeded  by  a 
descent  of  such  a  character  as  to  afford  evidence  that  at  the 
point  investigated  the  thoracic  wall,  instead  of  bulging,  is  re- 
tracted during  the  systolic  effort.  This  phenomenon,  which 
is  well  known  to  pathologists,  being  so  marked  in  some  con- 
ditions of  disease  that  it  is  easily  appreciated  b}'  the  unaided 
hand  or  eye,  has  been  called  the  "  negative  impulse."  It  means 
that  the  heart,  which,  when  gradually  filling  with  blood  applies 
itself  to  the  whole  prsecordia,  gathers  itself  from  all  directions 
towards  the  centre  of  impulse — in  bedside  language,  commonly 
miscalled  the  apex.  If  the  cardiographic  tracing  of  the  im- 
pulse is  compared  with  that  obtained  manometrically  by  a 
method  to  be  immediately  described,  it  is  obvious  that  the  two 
correspond  with  each  other  very  closely  ;  so  that  we  are  per- 
fectly safe  in  assuming,  as  has  been  done  above,  that  the  ascent 
denotes  the  beginning,  the  descent  the  end,  of  the  ventricular 
effort.  We  can  thus  determine  with  the  greatest  precision  the 
moment  at  which  the  mitral  and  tricupsid  valves  close.  The 
moment  of  the  closure  of  the  arterial  valves  is  not  so  certain, 
for  it  does  not  coincide  with  the  end  of  the  systole.  It  is 
sometimes  marked  b}T  an  up-and-down  movement  of  the  lever, 
due  to  the  vibration  into  which  the  chest  wall  is  thrown  at  the 
moment  that  the  curtains  of  the  aortic  valve  come  together. 
The  auricular  contraction  is  often  indicated  by  a  slight  eleva- 
tion, which  precedes  the  impulse  by  a  distinct  interval. 

61.  Investigation  of  the  Sounds  of  the  Heart. — The 
sounds  of  the  heart  can  be  studied  both  in  man  and  in  the 
lower  animals.  The  first  or  dull  sound  coincides  with  the 
hardening  of  the  ventricles,  the  complete  closure  of  the 
auriculo-ventricular  valves,  and  the  bursting  open  of  the  arte- 
rial orifices. 

It  is  caused  principally  by  the  sudden  distension  of  the  ven- 
tricles, but  can  be  proved  experimentally  to  be  also  in  part  of 
the  same  nature  with  the  noise  made  by  all  muscles  in  the  act 
of  contracting  against  a  resistance.  The  second  or  sharp  sound 
is  coincident  with  and  caused  by  the  closure  of  the  sigmoid 
valves.  This  is  proved  by  the  observation  that  if  the  valve  is 
injured,  or  prevented  from  closing  by  mechanical  means,  the 
sound  is  no  longer  heard.  In  studying  the  sounds  of  the  heart 
in  the  lower  animals,  particularly  in  the  dog,  the  student  of 
medicine  should  direct  his  attention  specially  to  the  modifica- 
tions of  the  sounds  under  known  conditions — e.g.,  in  dysp- 
noea, when  the  heart  is  distended  with  blood  ;  after  hemorrhage, 
when  the  ventricles  are  insufficiently  filled  in  diastole ;  after 
section  of  the  vagi,  when  the  frequency  of  the  contractions  is 


BY    DR.    BURDON-SANDERSON.  267 

so  great  that  the  aortic  valves  have  not  even  time  to  close,  or 
under  the  various  conditions  in  which  these  nerves  are  directly 
or  indirectly  excited.  From  all  these  modifications,  the  effi- 
cient causes  of  -which  are  known  and  understood,  lessons  ma3r 
be  learnt  which  may  be  applied  directly  at  the  bedside  as  aids 
in  the  interpretation  of  analogous  phenomena  when  they  pre- 
sent themselves  in  man. 

62.  Study  of  the  Action  of  the  Valves  in  the  Dead 
Heart. — Although  this  method  forms  no  exception  to  the 
general  rule  that  little  can  be  learnt  in  physiology  by  teleo- 
logical  inferences  from  the  properties  of  dead  organs  or  tis- 
sues, it  is  yet  of  great  value  to  the  student  for  the  purpose  of 
illustrating  the  purely  mechanical  part  of  the  action  of  the 
heart.  The  heart  of  any  mammalian  animal  may  be  used,  that 
of  the  pig  being  most  suitable.  The  simplest  method  of  imi- 
tating the  conditions  which  actually  exist  in  the  circulation, 
consists  in  bringing  one  or  other  of  the  ventricles  into  commu- 
nication with  a  reservoir  placed  at  a  sufficient  height  above  it 
b}r  means  of  two  flexible  tubes.  The  most  convenient  form  to 
be  given  to  the  reservoir  is  that  of  a  glass  funnel,  the  stem  of 
which  communicates  by  one  of  the  flexible  tubes  with  the  aorta. 
The  other  tube  ends  in  a  large  glass  canula,  which  is  secure^ 
tied  into  the  ventricle  near  its  apex ;  its  opposite  end  is  fitted 
to  a  glass  s}'phon,  the  short  leg  of  which  dips  into  a  funnel  ; 
the  tube  is  guarded  by  a  clip.  The  funnel  and  syphon  having 
been  filled  with  water,  and  the  clip  closed,  the  apparatus  is 
ready.  On  opening  the  clip,  water  flows  into  the  right  ven- 
tricle and  distends  it ;  on  closing  it  and  compressing  the  ven- 
tricle with  the  hand,  its  contents  are  forced  upwards  through 
the  aorta  into  the  funnel,  while  the  tricuspid  valve  is  distended. 
To  observe  the  action  of  that  valve,  all  that  is  necessary  is  to 
cut  away  part  of  the  wall  of  the  right  auricle.  It  is  then  seen 
that,  when  the  ventricle  is  squeezed,  the  liquid  contained  in  it 
tends  to  rush  outwards  by  the  auriculo-ventricular  opening, 
carrying  the  valve  with  it.  In  a  moment  the  curtains  become 
distended,  meeting  by  their  borders  so  as  to  form  a  tense  mem- 
branous dome,  which  projects  into  the  auricle.  The  time  which 
intervenes  between  the  commencement  of  the  compression  and 
the  tightening  of  the  valve  varies  according  to  the  vigor  of  the 
contractions,  the  quantit}'  of  blood  contained  in  the  ventricle, 
and  the  previous  position  of  the  valve,  but  must  alwa3's  be  ap- 
preciable. It  corresponds  to  the  praesystolic  period  previously 
referred  to.  All  these  facts  are  learnt  much  more  impressively 
by  introducing  the  index  finger  into  the  right  auricle  of  a  large 
animal.  In  the  horse  this  can  be  done  easily  by  an  opening 
of  such  size  that  the  finger  is  tightly  grasped  by  it.  The  valve 
bulges  out  as  a  tense  membranous  dome  into  the  auricle  at  the 
moment  of  auricular  contraction.     In  observing  the  action  of 


268  CIRCULATION   OF    THE    BLOOD. 

the  tricuspid  valve  in  the  dead  heart,  it  is  important  to  notice 
what  are  the  conditions  which  render  the  valve  incompetent, 
i.  e.,  prevent  it  from  closing  completely.  The  most  important 
of  these  conditions  is  over-distension  of  the  ventricle,  by  which 
the  ostium  becomes  too  large  to  be  covered  by  the  valve. 
When  this  occurs  during  life,  the  phenomenon  known  as  the 
venous  pulse  presents  itself.  The  right  ventricle  being  still  in 
communication  with  the  venous  system  at  the  moment  that  it 
hardens,  blood  is  injected  by  it  backwards.  When,  in  the 
human  subject,  this  condition  is  permanent,  it  leads  first  to 
dilatation  of  the  great  veins,  and,  secondly,  to  similar  incom- 
petence of  the  vein-valves  nearest  the  heart.  In  such  persons 
two  large  swellings  are  seen  on  either  side  of  the  neck — the 
distended  jugular  veins — which  pulsate  nearly  synchronously 
with  the  heart. 


Section  VI. — Endocardial  Pressure. 

By  this  term  is  understood  the  pressure  exercised  by  the 
blood  contained  in  the  heart,  against  its  internal  surface.  It 
can  be  measured  in  the  frog  and  in  mammalia. 

63.  Investigation  of  the  Endocardial  Pressure  in 
the  Heart  of  the  Frog  under  various  Conditions. — In 
the  frog  the  action  of  the  heart  is  maintained  unimpaired  after 
the  separation  of  the  organ  from  the  cerebro-spinal  nervous 
centres.  It  is  not  even  necessary  that  it  should  be  supplied 
with  blood.  Serum  (if  perfectly  fresh)  of  another  animal  may 
be  substituted  for  it,  without  apparently  affecting  either  the 
vigor  or  regularity  of  the  cardiac  contractions.  These  two 
facts  render  it  possible  to  use  the  heart  of  the  frog  for  the  solu- 
tion of  a  number  of  problems,  in  reference  to  which  it  is  desira- 
ble to  investigate  the  mechanical  functions  of  the  heart  inde- 
pendentty  of  the  influence  of  the  nervous  S3rstem. 

The  method  of  preparing  the  heart  for  such  experiments  is 
that  first  employed  by  Dr.  Coats,  of  Glasgow,  in  an  investiga- 
tion relating  to  the  mechanical  work  done  by  the  heart  in  a 
given  time,  in  Lud wig's  laboratory.  It  has  been  since  used 
with  various  modifications  by  Bowditch,  Brunton,  Blasius,  and 
others.  The  brain  and  spinal  cord  having  been  destroyed  by 
the  introduction  of  a  needle,  the  body  of  the  frog  is  cut  across 
below  the  liver.  The  sternum  with  the  anterior  extremities 
are  removed,  great  care  being  taken  to  reserve  on  one  side  a 
large  flap  of  skin  which  ma,y  be  used  as  a  cover  for  the  nerves 
and  the  heart.  The  heart  is  then  freed  of  its  pericardium,  and 
the  little  serous  ligament  by  which  it  is  connected  witli  the 
posterior  surface  of  that  membrane  is  ligatured  and  divided. 
The  next  step  is  to  tie  one  branch  of  the  aorta,  and  then  to  pass 
a  canula  through  the  other  and  the  bulb  into  the  ventricle.    The 


BY    DR.    BURDON-S ANDERSON.  269 

suspensory  ligaments  of  the  liver  are  then  severed  so  as  to  ex- 
pose the  vena  cava  inferior.  A  ligature  is  passed  round  that 
vessel,  which  is  then  slit  open  so  as  to  allow  a  large  canula  to 
pass  into  the  right  auricle.  The  canula  having  been  secured, 
the  liver  and  lungs  are  removed,  the  stomach  is  severed  through 
the  middle,  and  a  stout  glass  rod,  tapering  at  either  end,  is 
passed  from  the  mouth  down  the  oesophagus.  This  rod  should 
be  as  large  as  possible,  as  the  stretching  of  the  parts  between 
the  heart  and  the  spinal  column  which  is  thus  produced  mate- 
rial^ facilitates  their  satisfactory  exposure.  The  end  of  the 
glass  rod  which  projects  from  the  mouth  must  then  be  fixed  in 
a  support,  and  the  tube  which  is  inserted  in  the  right  auricle 
be  fitted  with  a  flexible  tube  and  connected  with  a  glass  reser- 
voir (for  which  purpose  one  of  the  patent  syphon  inkstands 
does  best)  filled  with  reddish  rabbit  serum.  The  aorta  is  in 
like  manner  connected  with  a  manometer  of  the  form  indicated 
in  fig.  233,  from  which  the  general  arrangement  of  the  heart, 
reservoir,  and  manometer  will  also  be  best  understood. 

The  heart  is  charged  with  serum  and  brought  into  action  by 
filling  the  reservoir.  From  thence  the  liquid  fills  the  right 
auricle,  passes  therefrom  to  the  ventricle,  and  is  discharged  by 
it  into  the  manometer.  As  soon  as  it  is  seen  that  no  more  air 
bubbles  pass  through  the  proximal  limb  of  the  manometer 
(the  upper  end  of  which  is  connected  with  a  flexible  tube  for 
the  purpose  of  conveying  the  liquid  pumped  by  the  heart  to  a 
suitable  receptacle),  the  apparatus  is  ready.  The  mode  of  ex- 
periment may  be  varied  according  as  it  is  intended  merely  to 
measure  the  variations  of  endocardial  pressure  which  occur 
during  a  cardiac  period,  or  to  observe  the  modifications  which 
that  pressure  undergoes  under  different  mechanical  conditions. 

64.  a.  Variations  of  Endocardial  Pressure  which  occur 
during  each  Cardiac  Period. — To  observe  these,  the  heart 
must  communicate  exclusively  with  the  manometer,  the  prox- 
imal limb  of  which  with  the  tube  leading  to  it  from  the  ven- 
tricle, and  the  ventricle  itself,  must  form  one  cavity  filled  with 
serum  and  closed  towards  the  auricles  by  the  valve,  and  in 
the  opposite  direction  by  the  mercurial  column  and  a  clip,  by 
which  the  tube  connected  with  the  upper  end  of  the  proximal 
limb  is  guarded.  The  manometer  should  be  at  such  a  height 
that  when  the  pressure  is  greatest  the  top  of  the  proximal 
column  is  at  the  same  level  as  the  heart ;  and  the  quantity  of 
mercury  it  contains  must  be  adjusted,  by  addition  or  subtrac- 
tion, with  the  aid  of  a  capillary  pipette,  so  that  when  the  heart 
is  in  diastole  the  distal  column  is  still  about  a  millimetre 
higher  than  the  other.  The  reservoir  for  the  supply  of  serum 
must  now  be  placed  at  such  a  height  above  the  heart  that  the 
auricle  is  equal  to  that  existing  during  diastole  in  the  ven- 
tricle ;  and  inasmuch  as  this  has  been  already  arranged  at  a 


270  CIRCULATION    OF    THE    BLOOD. 

millimetre  of  mercury,  the  height  of  the  venous  column  of 
serum  must  be  about  half  on  inch  =  12  millimetres,  the  spe- 
cific gravity  of  mercury  being  about  twelve  times  that  of  serum. 
In  the  distal  column  of  the  manometer  is  a  glass  piston,  the 
upper  end  of  which  bears  a  horizontal  arm  arranged  in  the 
same  way  as  that  which  bears  the  writing  pencil  in  the  ordi- 
nary k3'mograph — the  main  differences  being  that  in  this  case 
the  manometer  is  much  smaller,  and  that,  in  order  to  avoid 
friction,  the  tracing  is  recorded,  as  in  the  sphygmograph,  on 
glazed  paper,  blackened  by  passing  it  over  the  flame  of  a 
paraffin  lamp.  The  record  so  obtained  is  shown  in  fig.  234. 
On  account  of  the  relative  slowness  of  the  movements  and  the 
inconsiderable  lumen  of  the  manometer,  the  curve  is  very  little 
modified  by  the  oscillation  proper  to  the  mercurial  column,  and 
is  therefore  a  true  representation  of  the  succession  of  changes 
of  pressure  which  take  place  in  the  ventricle.  We  learn  from 
it  that  in  the  frog  the  pressure  exercised  by  the  ventricle  on 
the  blood  it  contains  arrives  at  its  acme  somewhat  gradually, 
and  persists  for  an  appreciable  period  ;  and  that  when  the  heart 
relaxes,  the  subsidence  of  pressure  is  at  first  extremelj-  rapid, 
but  subsequently  somewhat  more  gradual.  The  rate  of  move- 
ment of  the  paper  being  40  centimetres  per  minute,  the  dura- 
tion of  each  systole  can  be  easily  measured. 

65.  b.  Modifications  of  the  Endocardial  Pressure  Curve 
under  various  Conditions. — For  the  purpose  of  investigating 
the  influence  of  various  mechanical  conditions  on  the  action  of 
the  heart,  and  particularly  of  changes  in  the  relation  of  the 
pressure  in  the  veins  and  that  in  the  arteries,  the  apparatus 
must  be  so  modified  that  the  ventricle,  instead  of  communi- 
cating exclusively  with  the  manometer,  pumps  the  liquid,  con- 
stantly supplied  to  it  from  the  venous  reservoir,  along  a  tube 
or  system  of  tubes  representing  the  arterial  system.  To  fulfil 
these  conditions,  all  that  is  necessary  is,  (1)  to  insert  the  arte- 
rial canula,  not  in  the  bulb,  but  in  the  left  aorta  (the  right 
being  tied),  so  as  not  to  interfere  with  the  play  of  the  aortic 
valve  ;  and  (2)  to  join  to  the  proximal  limb  of  the  gauge  an 
India-rubber  tube,  dilated  near  the  junction  into  an  elastic 
bulb,  and  ending  in  a  nearly  capillary  beak  of  glass,  the  pur- 
pose of  the  latter  being  to  furnish  the  required  resistance,  that 
of  the  former  to  render  the  discharge  as  nearly  equable  as  pos- 
sible— in  short,  to  replace  the  elasticity  of  the  arteries. 

The  advantage  of  this  arrangement  does  not  lie  in  the  cir- 
cumstance that  the  mode  of  action  of  the  heart  is  more  natural, 
for  it  makes  little  difference  to  that  organ  whether  the  liquid 
it  discharges  at  one  contraction  returns  to  it  during  the  next 
relaxation  or  is  pumped  forwards,  provided  that  the  pressures 
to  which  it  is  subjected  are  the  same  in  systole  as  in  diastole. 
It  is  rather  that  when  the  heart  is  so  arranged  that  liquid  is 


BY   DR.    BTJRDON-SANDERSON.  271 

pumped  through  it  continuously,  the  observer  has  it  in  his 
power  to  modify  the  arterial  pressure  (by  altering  the  resist- 
ance) without  modifying  the  venous  pressure,  and  vice  versa, 
and  so  to  reproduce  conditions  which  actually  exist  and  exer- 
cise a  most  important  influence  in  the  living  body. 

It  is  obvious  that  if  the  pressure  on  the  venous  side  of  the 
heart  is  nil,  no  progressive  movement  will  occur,  whatever  may 
be  the  resistance  in  the  arteries ;  and,  on  the  other  hand,  that 
if  the  pressures  on  the  two  sides  of  the  heart  are  equal,  there 
must  also  be  no  movement,  for,  the  auriculo-ventricular  valve 
remaining  open,  the  heart  would  act  as  in  the  previous  experi- 
ment, receiving  back  again  in  diastole  whatever  liquid  it  dis- 
charged during  s}rstole.  Between  these  two  extremes,  that  of 
equalit}'  of  venous  and  arterial  pressures  and  that  of  total 
want  of  pressure  in  the  auricles,  a  mean  relation  exists  which 
is  most  advantageous  to  efficient  action,  and  cannot  be  de- 
parted from  in  either  direction  without  impairment  of  effect. 
The  existence  of  this  ratio  of  greatest  efficiency  has  been  lately 
demonstrated  experimentally  by  Blasius;1  and  it  has  been  found, 
first,  that  for  every  value  of  arterial  resistance,  it  is  possible  by 
successive  trials  to  ascertain  what  venous  pressure  enables  the 
heart  to  contract  with  the  greatest  effect ;  and,  secondly,  that 
for  every  heart  there  is  a  certain  value  of  arterial  resistance 
which  is  most  advantageous.  The  mean  result  of  numerous 
observations  is,  that  the  frog's  heart  (rana  esculenta)  does  most 
work  when  it  is  opposed  by  an  arterial  pressure  of  about  35 
millimetres  of  mercury.  If  the  resistance  is  greater  than  this, 
the  heart  becomes  over-distended,  and  its  valves  incompetent. 

66.  Application  of  the  preceding  Methods  to  the 
Investigation  of  the  Problem  of  the  Mechanical 
Work  done  by  the  Heart  in  a  given  Time. — In  the 
preceding  paragraph,  the  expressions,  mechanical  "  effect"  of 
the  heart's  contractions,  and  "  work"  done  by  the  heart,  have 
been  used  without  explanation.  Before  proceeding  further,  it 
is  necessary  to  define  them.  The  work  done  by  the  heart  in 
any  given  time  is  equal  to  the  product  of  the  aortic  pressure 
and  the  quantity  of  blood  which  passes  through  the  aortic 
orifice  in  the  same  time.  To  illustrate  this,  it  is  necessary  to 
revert  to  the  experiment  described  in  §  46,  in  which  the  circu- 
lation is  maintained  artificially  in  the  frog  b}^  substituting  for 
the  heart  a  column  of  serum  of  sufficient  height.  In  this  case, 
so  long  as  the  height  of  the  column  remains  unaltered,  the 
work  done  in  carrying  on  the  circulation  truly  represents  that 
of  the  heart.  If  it  is  allowed  to  diminish,  the  rate  of  flow 
diminishes  with  it.     To  maintain  constancy  in  the  circulation, 

1  Am.  Frosch-ITerzen  angestellte  Versuche  uber  die  Ilerz-Arbeit,  etc. 
Fick'a  Arbeiten,  Wurzburg,  1872,  p.  1. 


272  CIRCULATION    OF    THE    BLOOD. 

the  liquid  discharged  by  the  sinus  venosus  must  he  constantly 
replaced  in  the  funnel  as  it  flows  out.  The  work  which  is  ex- 
pended in  doing  this  per  minute  is  the  work  by  which  tin;  cir- 
culation is  carried  on.  Thus,  supposing  the  height  of  the 
column  of  serum  to  be  400  millimetres,  and  that  it  is  found 
that  the  level  of  the  liquid  in  the  funnel  begins  to  subside 
when  not  supplied  at  such  a  rate  that  the  weight  of  serum 
flowing  through  the  aorta  during  one  second  is  equal  to  one- 
fifth  of  a  gramme,  then  the  force  expended  per  second  would 
be  that  required  to  raise  one-fifth  of  a  gramme  400  rnillimetres, 
i.e.,  one  gramme  to  the  height  of  a  metre  in  12.5  seconds,  or 
0.08  grammes  to  the  same  height  in  one  second  ;  and  this  re- 
sult has  been  arrived  at  in  accordance  with  the  proposition 
with  which  we  started,  by  multiplying  the  aortic  pressure 
(expressed  in  the  height  of  a  column  of  blood  corresponding 
to  it)  by  the  quantity  discharged  in  the  given  time. 

If  exact  information  were  attainable  as  to  the  quantity 
which  the  heart  actuall}-  discharges  at  a  stroke,  it  would  be 
possible  to  measure  the  quantity  of  work  done  by  the  heart  in 
the  maintenance  of  the  circulation  in  a  mammalian  animal, 
and  inferentially  in  man  ;  but  inasmuch  as  no  such  method  at 
present  exists,  no  estimate  can  be  given  which  possesses  even 
approximate  value.  In  the  frog,  however,  a  reliable  estimate 
can  be  made  b}r  the  methods  described  in  §  63,  whichever  form 
of  experiment  is  employed.  Thus,  when  the  heart  communi- 
cates exclusively  with  the  manometer,  the  work  which  the 
heart  is  made  to  do  is  to  raise  whatever  quantity  of  mereur3r 
is  contained  in  the  manometer  between  the  level  at  which  it 
stands  during  diastole  and  that  to  which  it  rises  in  systole,  to 
the  mean  height  height  £,  where  h  denotes  the  difference  in 
millimetres  of  the  two  levels.  For  evidently,  of  the  whole 
number  of  particles  of  mercury  in  the  distal  column,  the  sur- 
face of  which  is  caused  to  rise  /(  millimetres  above  the  surface 
in  the  proximal  column,  it  is  only  the  top  particles  which  are 
raised  h  millimetres  above  the  level  of  the  proximal  column  ; 
those  in  the  exact  middle  are  raised  only  half  h  ;  those  above 
and  below,  less  or  more  in  proportion  to  their  distance  from 
the  middle  ;  so  that  the  mean  elevation  is  half/?.  The  weight 
is  easily  known  if  we  know  the  aera,  i.  e.,  lumen,  of  the  tube, 
and  the  specific  gravity  of  the  mercur}'.  If  we  designate  the 
former  as  a  and  the  latter  as  s,  we  have  the  weight  lifted  by 
the  heart  in  each  contraction  to  the  height  £,  expressed  by  a 
s  h,  and  the  work  done  (that  is,  the  product  of  the  weight 
lifted  and  the  height  to  which  it  is  lifted)  — ".  If  it  is  desired 
to  obtain  perfectly  accurate  results,  a  manometer  must  be  used 
of  which  the  area  of  the  surface  of  the  mercury  in  the  proximal 
limb  is  relatively  very  large.  In  the  other  form  of  experiment, 
§  64,  i.e.,  when  a  continuous  current  of  serum  is  pumped  by 


BY    DR.    BURDOX-SANDERSON.  273 

the  heart  along  a  tube  representing  an  arterial  System,  the 
problem  assumes  a  somewhat  different  form.  The  rate  of  flow 
through  the  tube  must  be  first  ascertained  by  measuring  the 
discharge  from  its  terminal  orifice.  This  being  known,  the 
answer  to  the  question  is  arrived  at  by  considering  what 
height  of  column  of  serum  would,  if  substituted  for  the  heart, 
be  sufficient  to  determine  the  same  rate  of  efflux.  This  can 
be  learnt  most  accurately  by  a  comparative  experiment;  it 
can  be  deduced  approximately  from  the  measurement  of  the 
mean  pressure  actually  existing  in  the  aorta.  Here,  as  before, 
the  mechanical  Avork  done  by  the  heart  is  the  work  which 
would  be  required  to  raise  the  quantity  of  serum  discharged 
per  second  to  the  height  corresponding  to  the  pressure,  i.  e., 
to  a  height  something  like  twelve  times  that  indicated  by  the 
mercurial  manometer. 

67.  Investigation  of  the  Endocardial  Pressure  in 
Mammalia. — As  this  mode  of  investigation  can  only  be  prac- 
tised on  animals  of  large  size,  and  has  already  perhaps  yielded 
all  the  results  which  can  be  expected  from  it,  it  will  be  suffi- 
cient to  give  a  cursory  account  of  it  here,  referring  the  reader 
to  the  papers  of  its  author,  Professor  Chauveau,  for  detailed 
information.  The  method  consists  in  lodging  in  one  or  other 
of  the  cavities  of  the  heart  of  an  animal,  an  India-rubber  bag, 
or  ampulla,  which  communicates  by  a  long  narrow  tube  with  a 
manometer.  The  introduction  of  the  instrument  in  question 
(which  has  received  the  name  of  cardiac  sound)  into  the  right 
cavities  through  the  external  jugular  vein  is  perfectly  easy,  and 
can  be  effected  in  the  horse,  as  I  can  testify  from  my  own  ob- 
servation, without  occasioning  the  animal  the  slightest  suffer- 
ing or  even  inconvenience — a  fact  easily  enough  understood 
when  we  reflect  that  the  internal  surface  of  the  vascular  system 
is  not  supplied  with  sensory  nerves.  The  ampulla  does  not 
come  in  contact  with  the  surface  of  the  heart.  The  left  ven- 
tricle is  reached  through  the  carotid  artery  with  somewhat 
greater  difficult}'.     The  left  auricle  is  of  course  inaccessible. 

The  most  important  results  have  been  obtained  by  a  cardiac 
sound  so  constructed  that  the  variations  of  pressure  can  be 
recorded  in  the.  right  auricle  and  ventricle  simultaneously.  By 
means  of  this  instrument,  M.  Chauveau  has  been  able  to  demon- 
strate the  order  of  succession  of  the  movements  of  the  heart, 
and  the  intervals  of  time  which  separate  them  from  each  other, 
with  an  exactitude  which  would  have  been  otherwise  unattaina- 
ble. Thus  he  has  shown  that  in  the  horse  the  interval  between 
the  hardening  of  the  auricle  and  that  of  the  ventricle  is  just 
about  a  tenth  of  a  second,  and  that  the  duration  of  the  ven- 
tricular systole  is  about  three-tenths,  whatever  be  the  number 
of  contractions  per  minute;  so  that  frequency  of  the  pulse  de- 
pends not  on  the  time  taken  by  the  heart  to  accomplish  each 
18 


274  CIRCULATION   OF   THE    BLOOD. 

contraction,  but  on  the  interval  of  relaxation  which  separates 
one  systole  from  its  successor.     {See  fig.  2o.r).) 

Chauveau  found  the  systolic  pressure  in  the  horse  to  be  about 
128  millimetres  in  the  left  ventricle,  and  25  millimetres  in  the 
right.  These  numbers  express  the  relative  values  of  the  me- 
chanical work  done  by  the  two  ventricles.  The  absolute  values, 
as  has  been  already  stated,  are  unknown,  from  the  impossibility 
of  determining  the  quantity  of  blood  which  Hows  through  the 
heart  in  a  given  time. 

Section  VII. — Intrinsic  Nervous  System  of  TnE  Heart. 

Nothing  is  as  yet  known  either  as  to  the  anatomical  distribu- 
tion of  nervous  elements  in  the  hearts  of  mammalia,  or  as  to 
the  functions  which  they  perform.  In  the  frog,  both  have 
been  the  subject  of  minute  and  repeated  investigation.  We 
have  already  had  frequent  occasion  to  observe  that  the  frog's 
heart  continues  to  beat  after  its  removal  from  the  body,  and 
that  this  rhythmical  movement  often  goes  on  for  hours  or  even 
for  days,  under  favorable  circumstances.  From  this  it  is  evi- 
dent that  its  maintenance  is  dependent  on  conditions  which  are 
contained  within  the  heart  itself. 

68.  Proof  that  the  Ganglion  Cells  contained  in  the 
Heart  are  the  Springs  of  its  Automatic  Movement. — 
It  is  objected  b}^  some  physiologists  that  the  rhythmical  con- 
tractions go  on  not  merely  in  the  whole  heart  when  deprived 
of  blood  and  severed  from  the  cerebro-spinal  nervous  system, 
but  also  in  mere  fragments  of  the  muscular  substance  which 
cannot  be  admitted  to  contain  ganglion  cells.  The  answer  lies 
in  the  results  of  the  following  experiments: — 

The  heart  of  a  frog  just  removed  from  the  body  is  placed  in 
a  watch-glass  containing  serum,  or  three-fourths  per  cent,  saline 
solution,  in  which  it  will  continue  to  pulsate  for  many  hours. 
Small  portions  of  muscular  substance  are  then  taken  either  from 
the  sinus  venosas,  the  auricles,  or  the  ventricle,  and  observed 
in  a  drop  or  two  of  the  indifferent  liquid,  under  a  low  power. 
It  is  then  seen  that  portions  taken  from  the  sinus,  the  auricles, 
or  that  part  of  the  ventricle  which  is  in  the  immediate  neighbor- 
hood of  the  auriculo-ventricular  constriction,  pulsate  rhythmi- 
cally, but  that  similar  portions  taken  from  the  ventricle  near 
the  apex  do  not  pulsate.  The  pulsating  bits  may  be  further 
divided  with  sharp  scissors  under  the  dissecting  microscope, 
until  preparations  are  obtained  which  consist  of  only  a  few 
muscular  fibres.  Many  of  these  still  contract  rhythmically, 
each  fibre  becoming  shorter  and  thicker  at  each  contraction,  but 
not  losing  its  rectilinear  contour.  If  now  the  pulsating  and 
non-pulsating  shreds  are  submitted  to  microscopical  examina- 
tion, it  will  be  found  that,  whereas  ganglion  cells  cannot  be 


BY    DR.    BURDON-SANDERSON.  275 

seen  in  the  latter,  they  exist  as  a  rule  in  the  former.  In  the 
recent  state,  indeed,  it  is  quite  impossible  to  demonstrate  their 
presence  in  either  case,  but  they  can  be  detected  after  prepara- 
tion with  chloride  of  gold  in  the  manner  directed  in  Chap.  IV. 

69.  Description  of  the  Intrinsic  Nervous  System  of 
the  Heart  of  the  Frog. — The  heart  of  the  frog  is  not  known 
to  receive  nerves  from  any  source  excepting  the  vagus.  The 
cardiac  branches  of  this  nerve,  as  they  enter  the  heart  (see  § 
73),  apply  themselves  to  the  superior  vena  cava  close  to  its 
origin,  and  then,  after  giving  numerous  branches  beset  with 
ganglionic  cells  to  the  sinus  venosus,  the  two  nerves  combine 
to  form  a  plexus  at  the  upper  part  of  the  septum,  between  the 
auricles.  From  this  plexus  two  filaments  descend,  the  smaller 
along  the  anterior  edge  of  the  septum,  the  larger  along  the 
posterior.  On  approaching  the  auriculo-ventricular  orifice, 
each  of  them  exhibits  a  distinct  bulging  (Bidder's  ganglia), 
from  which  radiating  streaks  may  be  seen  to  spread  towards 
the  ventricle. 

So  long  as  the  nerves  are  still  outside  of  the  heart  they  do 
not  contain  any  ganglion  cells,  nor  give  off  any  branches  ;  but 
as  they  approach  the  plexus  they  become  beset  with  cells,  and 
give  off  numerous  filaments  to  the  sinus  venosus.  The  two 
branches  (anterior  and  posterior)  have  no  special  relation  to 
the  two  rami  cardiaci  from  which  they  in  common  originate, 
although  Bidder  finds  that  the  anterior  contains  more  fibres 
from  the  right  side,  the  posterior  from  the  left.  In  their 
course,  both  filaments  give  off  branches,  which  ramify  in  the 
septum  or  pass  into  the  wrall  of  the  auricles.  In  order  to  see 
these  nerves,  the  heart  must  be  exposed  by  opening  the  peri- 
cardium. Its  point  must  then  be  drawn  upwards,  the  two 
aortse  divided,  and  the  ligamentous  shred  which  connects  it 
with  the  posterior  surface  of  the  pericardium  cut  through. 
The  two  vense  cavae  must  then  be  divided  as  far  from  the  heart 
as  possible,  and  the  heart  removed.  If  the  organ  is  now 
stretched  on  a  wax  plate  by  means  of  fine  pins  stuck  into  the 
vena?  cavae,  one  into  the  vena  cava  inferior,  and  one  into  each 
vena  cava  superior,  and  examined  under  water,  the  two  vagi 
(rami  cardiaci)  can  be  seen  where  they  are  in  relation  with 
the  vena  cava  superior.  If  now  the  apex  is  drawn  to  the  right 
and  fixed  by  a  fourth  pin,  the  side  of  the  left  auricle  is  ex- 
posed, and  may  be  slit  open  with  fine  scissors,  so  as  to  bring 
into  view  the  septum,  which  must  then  be  cleared  of  the  outer 
wall  of  the  auricle  by  careful  dissection.  Fig.  236  shows  the 
appearance  of  the  septum  prepared  in  this  wa}r. 

70.  Demonstration  of  the  Special  Functions  of  the 
Ganglia.  1.  Slannius's  Experiment. — The  heart  of  a  frog 
having  been  exposed  in  the  usual  way,  a  short  glass  rod  is 
introduced   into   the  oesophagus.     All   the  other  organs  may 


276  CIRCULATION    OF   THE    BLOOD. 

now  be  removed  in  the  manner  directed  in  §  03,  care  being 
taken  to  avoid  interfering  with  tlie  vena-  cava*.  The  glass 
rod  having  now  been  fixed  horizontally  on  the  table,  and  the 
oesophagus  secured  by  pins  stuck  through  it  into  the  table  so 
as  to  prevent  it  from  slipping  on  the  rod,  the  apex  of  the 
heart  is  seized  with  blunt  forceps  and  drawn  forwards  and  to 
the  right.  A  silk  ligature  is  then  passed,  with  the  aid  of  the 
needle  shown  in  fig.  203£>,  between  the  vena  cava  inferior  and 
the  ventricle,  and  between  the  vena;  cava?  superiores  and  the 
right  auricle,  in  such  a  position  that  when  it  is  tightened  it 
will  grasp  the  line  of  junction  between  the  sinus  venosus 
and  the  right  auricle.  The  ligature  having  been  looped  by  an 
assistant  and  carefully  adjusted  in  the  proper  position,  the 
heart  is  left  to  itself.  As  soon  as  it  is  seen  that  it  is  con- 
tracting regularl}',  the  ligature  is  tightened.  After  one  or  two 
beats,  the  heart  stops  in  a  state  of  relaxation.  The  pulsations 
of  the  sinus,  however,  continue  at  the  same  rate  as  before. 
After  a  time  the  ventricle  also  begins  to  beat ;  but  on  com- 
paring its  rhythm  with  that  of  the  sinus,  it  is  seen  that  they 
do  not  agree. 

2.  In  another  heart,  prepared  in  the  same  manner,  the  sinus 
is  cut  off  from  the  right  auricle,  the  line  of  amputation  corre- 
sponding with  that  of  the  ligature  in  1.  In  doing  this,  the 
heart  must  be  drawn  forwards  with  the  forceps  by  its  apex  as 
above  directed.  The  result  is  more  striking  when  the  scissors 
used  are  not  very  sharp. 

3.  If  in  either  of  the  above  experiments  the  ventricle  is  cut 
off  from  the  auricles  immediately  after  the  ligature  or  amputa- 
tion, as  the  case  may  be,  it  begins  to  beat  again  at  once. 

4.  In  a  third  heart,  the  line  of  ligature,  i.  e.,  the  junction 
between  the  sinus  venosus  and  the  right  auricle,  is  excited  by 
the  induced  current.  For  this  purpose  Du  Bois  Reymond's 
induction  apparatus  is  used.  The  points  of  the  excitor  must 
be  very  close  to  each  other.  The  effect  resembles  that  of  the 
ligature.  If  the  electrodes,  instead  of  being  placed  so  as  to 
include  the  sinus,  are  applied  to  the  auricles,  no  effect  is 
produced. 

5.  In  another  animal,  TTn>o  °f  a  grain  of  atropin  (or  less)  is 
injected  underneath  the  skin.  After  a  few  minutes  the  heart 
is  removed,  and  experiment  4  is  repeated.  The  electrical  exci- 
tation produces  no  effect,  the  ganglion  of  the  septa  being  para- 
lyzed. Experiment  1  is  then  repeated.  The  heart  stops  as 
before. 

All  the  preceding  results  can  be  obtained  in  the  separated 
heart.  The  method  recommended  facilitates  the  manipulation 
without  in  the  slightest  degree  impairing  the  value  of  the  re- 
sults. Stannius's  experiment  admits  of  two  different  explana- 
tions, which  are  not,  however,  inconsistent  with  each  other: — 


BY    DR.    BURDON-SANDERSON.  277 

1.  The  arrest  of  the  heart  may  be  regarded  as  a  result  of 
the  excitation  of  the  ganglion  of  the  septum,  i.  e.,  the  mechani- 
cal irritation  of  that  part  produced  by  the  scissors  or  ligature  ; 
in  other  words,  as  an  effect  of  the  same  nature  as  that  pro- 
duced in  experiment  4,  where  that  centre  is  subjected  directly 
to  electrical  stimulation;  or, 

2.  It  is  dependent  on  the  severance  of  the  sinus  venosus 
from  the  rest  of  the  heart.  In  this  case  it  must  be  regarded 
as  of  a  different  nature  from  the  arrest  produced  by  electrical 
excitation. 

If  it  were  not  for  experiment  5,  we  should  be  inclined  to 
adopt  the  former  of  these  views  :  for  it  is  very  easy  to  imagine 
that  it  is  not  likely  to  make  much  difference  whether  we 
squeeze  the  ganglion  with  a  ligature,  nip  it  between  the  blades 
of  a  pair  of  scissors,  or  excite  it  by  Faradaic  electricity.  In- 
deed, any  one  who  compares  the  two  results — the  arrest  of 
the  heart  by  electrical  excitation  of  the  sinus  on  the  one  hand, 
and  that  produced  by  ligature  across  the  upper  part  of  the 
auricles  on  the  other — would  probably  at  once  decide  on  their 
identity.  By  previously  subjecting  the  heart  to  the  influence 
of  atropin,  we  are  enabled  to  demonstrate  that  such  a  conclu- 
sion would  be  erroneous  ;  for  if  the  effect  of  ligature  were  of 
the  same  nature,  it  would  be  counteracted  by  the  same  agency. 

In  order  to  explain  the  phenomena,  it  is  necessary  to  assume, 
what  has  not  }Tet  been  proved  anatomically,  namely,  that  the 
venous  sinus  contains  an  automatic  motor  centre.  By  this 
term  we  understand  (in  accordance  with  the  general  notions 
entertained  as  to  r3rthmical  action)  a  ganglionic  centre, in  which 
energy  tends  to  accumulate  and  discharge  itself  in  the  form 
of  motion  at  regular  intervals,  the  length  of  which  varies  (a) 
with  the  resistance  to  the  discharge,  and  (b)  with  the  rapidity 
of  accumulation. 

The  phj'siological  ground  for  this  assumption  of  the  exist- 
ence of  a  motor  centre  in  the  sinus  venosus  is,  first,  that  the 
succession  of  acts  which  make  up  a  cardiac  contraction  com- 
mences distinctl}'  in  the  sinus,  and  that  it  is  the  only  part  of 
the  heart  which  contracts  independent!}',  i.e.,  without  being 
affected  by  the  action  of  any  other  part  of  the  organ;  and, 
secondly,  that  electrical  stimulation  of  the  sinus  induces  in- 
creased frequency  of  the  contractions  of  the  whole  organ.  Ad- 
mitting the  existence  of  such  a  centre,  and  assuming  also  that 
the  ganglion  of  the  vagus,  situated,  as  we  have  seen  it  to  be, 
close  to  the  line  of  ligature  or  amputation  on  the  auricular 
Bide  of  it,  has  the  power  of  inhibiting,  i.e.,  increasing  the  re- 
sist ance  to  the  discharges  from  that  centre,  and  further  that 
it  exercises  a  similar  inhibitory  influence  on  the  motor  ganglia 
at  the  base  of  the  ventricle,  we  are  enabled  to  harmonize  the 
experimental  results  completely  thus:  In  the  ligature  and  am- 


278  CIRCULATION  OF  THE  BLOOD. 

putation  experiments,  the  heart  stops  for  two  reasons:  first, 
because  the  ventricle  is  separated  from  the  motor  centre;  and, 
secondly,  because,  by  the  pressure  or  mechanical  irritation  of 
the  ligature  or  blunt  scissors,  the  vagus  ganglion  is  excited. 
In  electrical  excitation,  on  the  other  hand,  the  second  of  these 
effects  is  produced  without  the  first ;  consequently,  when  under 
the  influence  of  atropin,  the  vagus  ganglion  is  paralyzed — the 
influence  of  ligature  and  amputation,  in  so  far  as  they  are  de- 
pendent on  severance  of  the  sinus  from  the  rest  of  the  heart, 
are  unaltered,  but  electrical  excitation  is  without  result. 

On  this  subject  the  student  will  do  well  to  consult  the  ori- 
ginal papers,  the  references  to  which  are  as  follows  :  As  regards 
the  anatomy  of  the  ganglia,  the  most  important  paper  is  that 
of  Bidder,  in  Midler's  Archiv,  1852,  p.  1G3;  as  regards  their 
functions,  Stannius  (Midler's  Archiv,  1852,  p.  85),  Nawrocki 
(Der  Stanniusche  Herzversuch,  Heidenhain's  Studien,  1861,  p. 
110),  and  Schmiedeberg  (Untersuch.  liber  einige  (jiftwirkungen 
am  Froschhcrzen.     Ludwig's  Arbeiten,  1871,  p.  41). 

71.  Study  of  the  Influence  of  Changes  of  Tempe- 
rature on  the  Heart. — (a)  In  the  Frog.  Inasmuch  as  the 
influence  of  temperature  is  obviously  dependent  on  the  in- 
trinsic nervous  system,  the  present  is  the  proper  time  for  con- 
sidering it.  The  modes  of  investigation  are  the  same  as  those 
already  described  in  the  section  on  endocardiac  pressure.  Ex- 
act and  extended  researches  have  been  made  by  both  of  the 
methods  there  given,  the  first  having  been  employed  by  Cyon, 
the  second  by  Blasius.  Of  the  two,  the  latter  is  preferable,  on 
account  of  the  greater  ease  with  which  the  work  done  can  be 
measured.  The  general  result  is,  firstl}',  that  the  quantity  of 
mechanical  work  which  can  be  done  by  the  heart  in  a  given 
time  increases  with  the  temperature  up  to  a  certain  point 
(about  20°  C,  but  it  differs  in  different  animals,  and  no  doubt 
also  at  different  seasons),  so  that  it  may  be  doubled  or  trebled 
by  a  gradual  rise  from  ordinary  winter  temperature  to  that  of 
summer;  and,  secondly,  that  under  the  same  circumstances 
the  frequency  of  the  contractions  increases  in  much  greater 
proportion  than  the  mechanical  effect.  Hence  it  results  that, 
although  the  total  quantity  of  work  done  in  a  given  time  is 
less  at  lower  temperatures  than  at  higher,  the  effect  of  each  in- 
dividual contraction  is  much  greater. 

If  it  is  desired  merely  to  observe  the  effect  of  changes  of 
temperature  on  the  frequency  of  the  pulse,  much  simpler  ap- 
paratus will  answer  the  purpose.  Either  the  whole  heart  may 
be  used  or  a  part  of  it.  In  the  former  case,  the  organ  having 
been  removed  from  the  body  is  suspended  by  a  thread  attached 
to  the  aorta  in  the  interior  of  a  tolerably  wide  test-tube  fur- 
nished with  a  cork,  through  the  centre  of  which  the  thread  is 
drawn.     At  the  bottom  of  the  tube  there  is  a  bit  of  blotting- 


BY    DR.    BURDON-SANDERSON.  279 

paper,  soaked  with  water.  The  "  moist  chamber"  so  prepared 
is  immersed  vertically  in  a  test  tube  filled  with  cold  water, 
which  also  contains  a  thermometer.  The  water  in  the  beaker 
is  then  very  gradually  warmed,  while  its  temperature  and  the 
frequency  of  the  contractions  of  the  heart  are  noted  from  time 
to  time.  It  is  then  seen  that  the  frequency  gradually  increases 
up  to  about  34°  C,  above  which  the  contractions  become  ir- 
regular, and  are  difficult  to  count  with  exactitude,  until  at  last 
the  condition  known  as  "  heat  rigor"  (with  reference  to  which 
see  Chapter  XX.)  supervenes.  Similar  observations  may  be 
made  with  respect  to  portions  of  the  heart,  as,  e.  #.,  the  base 
of  the  ventricle  or  the  sinus  venosus.  For  this  purpose  it  is 
convenient  to  place  the  fragment  on  a  cover  glass  in  a  drop 
of  serum,  and  invert  it  over  the  chamber  of  Strieker's  warm 
stage. 

72.  (b)  In  Mammalia. — From  the  observation  of  the  very 
remarkable  effects  which  diminution  and  increase  of  the  in- 
ternal temperature  of  the  body  respectively  produce,  the  one 
in  diminishing,  the  other  in  increasing,  the  frequency  of  the 
pulse  inrabbits  and  dogs,  it  seems  probable  that  the  mammalian 
heart  is  more  sensitive  to  temperature  changes  than  that  of  the 
amphibia.  As,  however,  it  is  not  possible  to  eliminate  the  in- 
fluence of  the  central  nervous  system,  this  cannot  be  proved 
experimentally. 

Section  VIII. — The  Inhibitory  Nerves  of  the  Heart. 

73.  1.  Demonstration  of  the  Influence  of  the  Vagus 
Nerve  on  the  Heart  in  the  "Frog.— Description  of  the 
Vagus  Nerve. — The  vagus  nerve  originates  in  the  frog  from 
the  posterior  aspect  of  the  medulla  oblongata  by  three  or  four 
roots,  the  lowest  (analogous  to  the  spinal  accessory)  being 
more  to  the  front  than  the  rest.  The  nerve  passes  out  of  the 
cranial  cavity  through  the  condyloid  foramen  of  the  occipital 
bone,  outside  of  which  it  forms  a  ganglion,  and  is  in  close 
relation  with  the  sympathetic  trunk.  After  leaving  the  sym- 
pathetic (see  fig.  237),  it  divides  into  two  branches,  of  which 
the  anterior  contains  the  glossopharyngeal,  the  posterior  the 
nerves  which  are  distributed  to  the  heart,  lungs,  and  other 
viscera.  The  vagus  itself  and  its  cardiac  branch  run  along- 
side of  and  in  the  same  direction  with  the  lower  of  the  three 
petrohyoid  muscles,  as  far  as  the  extremity  of  the  posterior 
horn  of  the  hyoid  bone,  into  which  the  muscle  is  inserted. 
During  this  part  of  its  course  it  is  accompanied  "by  the  laryn- 
geal nerve,  which  leaves  it  just  before  it  reaches  the  insertion 
of  the  muscle.  At  about  the  same  point  it  crosses  the  apex  of 
the  lung,  passing  behind  the  pulmonary  artery,  and  gives  off 
pulmonary  branches  which  accompany  that  vessel.      Having 


280  CIRCULATION   OF   THE    BLOOD. 

crossed  the  lung,  the  nerve  finds  its  way  directly  to  the  sinus 
venosus,  but  is  so  surrounded  with  gray-looking  connective 
tissue,  that  in  small  frogs  it  is  difficult  to  trace  it.  As  it 
enters  the  heart  it  is  closely  applied  to  the  superior  vena  cava 
and  to  the  wall  of  the  sinus. 

74.  Method. — A  frog,  having  been  slightly  curarizcd  or 
rendered  motionless  by  section  of  the  medulla,  is  fixed  in  the 
prone  position.  The  sternum  is  then  divided  in  the  middle 
line,  and  the  two  halves  of  the  wall  of  the  chest  drawn  to 
either  side,  so  as  to  expose  the  pericardium  and  lungs,  while  a 
stout  glass  rod  is  passed  down  the  oesophagus.  The  following 
objects  (.see  fig.  237)  are  then  seen  :  1.  The  two  aorta?,  parting 
from  each  other  in  the  middle  line,  ascend  outwards  and  up- 
wards close  to  the  cartilaginous  tips  of  the  posterior  horns  of 
the  hyoid  bone.  2.  From  each  of  these  horns  muscular  fibres 
are  seen  to  stretch  backwards  and  upwards,  towards  the 
occipital  region;  these  are  the  petrohyoid  muscles  already 
mentioned,  which  originate  from  the  petrous  bone,  and  are 
inserted  into  the  cartilaginous  processes  just  referred  to.  The 
lower  of  these  nearly  parallel  bundles  of  fibres,  is  the  guide 
to  the  vagus  nerve,  which  always  lies  along  its  lower  edge.  3. 
Following  the  muscles  backwards,  they  are  seen  to  be  crossed 
by  a  white  nervous  cord  (the  hypoglossal  nerve),  which  ascends 
upwards  and  inwards  towards  the  muscles  of  the  tongue. 
Nearer  the  middle  line,  lying  somewhat  further  from  the 
surface,  but  following  the  same  general  direction,  another 
nerve  is  seen,  the  glossopharyngeal.  4.  Crossing  upwards  to 
the  larynx,  over  the  tip  of  the  inferior  horn  of  the  hyoid,  the 
laryngeal  nerve  is  seen.  This  is  the  onl}'  nerve  which  is  likely 
to  be  mistaken  for  the  vagus  ;  it  must  therefore  be  traced  back 
for  a  short  distance  from  the  cartilage  and  divided.  It  is 
convenient  also  to  get  rid  of  the  hypoglossus. 

The  vagus,  with  the  muscular  slip  which  accompanies  it,  can 
now  be  readily  placed  on  or  between  the  electrodes.  On 
opening  the  ke}',  the  heart  usually  stops  in  diastole,  with  its 
cavities  full  of  blood,  the  arrest  not  being  preceded  by  any 
previous  slowing.  If,  however,  Helmholtz's  arrangement  of 
the  induction  apparatus  is  used,  and  the  secondary  coil  is 
placed  at  a  sufficient  distance,  a  degree  of  excitation  ma}'  be 
attained  which,  while  it  falls  short  of  stopping  the  heart,  is 
enough  to  diminish  its  frequency.  With  reference  to  this 
effect,  it  is  to  be  noticed  that,  although  it  is  mainly  due  to 
mere  lengthening  of  the  diastolic  intervals,  it  is  also  accompa- 
nied with  an  impairment  of  the  vigor  of  the  ventricular 
systole;  so  that  if  the  heart  is  connected  with  a  manometer 
(see  §  G3),  the  manometer  rises  less  during  the  period  of  slow- 
ing than  it  did  before.      Another  interesting  and  important 


BY    DR.    BURDON-SAXDERSON.  281 

fact  is,  that  the  effect  does  not  attain  its  maximum  till  several 
seconds  after  the  commencement  of  the  excitation. 

[In  this  and  all  other  experiments  in  which  it  is  desired  to 
note  the  time  which  elapses  between  the  application  of  a 
stimulus  and  its  effect,  we  use  the  electrical  indicator.  It  is 
an  arrangement  exactly  similar  to  an  electrical  bell,  with  the 
exception  that  the  hammer,  instead  of  striking  a  bell,  writes 
on  the  recording  cylinder  of  the  kymograph.  By  a  simple 
mechanical  arrangement,  the  same  act  which  opens  the  Du 
Bois'  key  closes  another  circuit,  of  which  the  electro-magnet 
of  the  indicator  forms  part,  and  vice  versa.  This  being  the 
case,  the  instrument  makes  vertical  strokes  on  the  cylinder  at 
the  moment  that  the  excitation  of  the  nerve  begins  and  ends.] 

75.  2.  Demonstration  of  the  Influence  of  the  Vagus 
Nerve  on  the  Heart  in  Mammalia.— In  mammalia,  the 
inhibitor}'  nerves  contained  in  the  vagi  are  in  constant  action, 
consequently  division  of  both  vagi  produces  acceleration  of 
the  contractions  of  the  heart.  In  the  dog,  this  effect  is  much 
more  considerable  than  in  the  rabbit,  and  is  attended  with  an 
increase  of  the  arterial  pressure,  which  in  the  latter  is  absent 
(see  fig.  238).  On  the  other  hand,  electrical  excitation  of  the 
vagus,  whether  previously  divided  or  not,  retards  the  contrac- 
tions of  the  heart  in  all  animals,  and,  if  the  induced  current  is 
strong  enough,  arrests  the  organ  in  diastole.    (See  fig.  239  a,  6.) 

To  show  these  facts  in  the  rabbit,  all  that  is  necessary  is  to 
narcotize  the  animal,  to  insert  a  needle  in  the  heart  at  the 
upper  part  of  the  praecordia  (i.  e.,  about  an  inch  to  the  left  of 
the  middle  line,  at  the  level  of  the  third  cai'tilage),  and  to  ex- 
pose the  vagi  on  both  sides  of  the  neck.  If,  now,  either 
nerve  is  placed  between  the  electrodes,  and  the  key  opened, 
the  movement  of  the  needle  either  stops,  becomes  irregular, 
or  is  mereby  retarded  and  diminished  in  extent,  according  to 
the  strength  of  the  current.  To  observe  the  effect  of  section, 
loose  ligatures  must  be  placed  round  both  nerves,  and  the 
animal  then  left  to  itself,  while  the  number  of  pulsations  per 
fifteen  seconds  is  carefully  counted.  The  two  nerves  are  then 
divided  at  once,  and  the  countings  repeated.  The  increase  of 
frequency  usually  amounts  to  about  twenty  percent.  Finally, 
the  peripheral  end  of  one  nerve  is  excited,  and  the  same  effects 
produced  as  by  excitation  of  the  undivided  trunk. 

In  demonstrating  the  influence  of  the  vagus  on  the  heart  in 
the  dog,  it  is  desirable  to  connect  the  carotid  or  crural  artery 
with  tlic  kymograph  ;  for  the  most  important  effects  are  those 
which  relate  to  the  changes  in  the  arterial  pressure.  The  pre- 
liminary steps  of  the  experiment  are  those  described  in  §  34. 
Loose  ligatures  having  been  placed  round  both  vagi,  and  a 
kymographic  observation  made,  to  determine  the  normal  arte- 
rial  pressure  and   frequency  of  the   pulse,  both    nerves  are 


282  CIRCULATION   OF    THE    BLOOD. 

divided  simultaneously.  The  mercurial  column  at  once  rises, 
mid  the  contractions  of  the  heart  become  so  frequent,  that  the 
oscillations  can  no  longer  be  followed  by  the  eye,  all  that  can 
be  distinguished  being  a  vibratile  movement  of  the  column. 
On  exciting  the  peripheral  end  of  either  vagus,  the  same  effects 
are  produced  as  in  the  rabbit.  If  the  current  is  sufficiently 
strong  to  stop  the  heart,  the  mercurial  column  sinks  rapidly, 
inscribing  a  parabolic  curve  on  the  paper  (fig.  2:>!)/;).  the  exact 
form  of  which  depends  on  the  condition  of  the  arterial  system  ; 
the  rate  of  descent  varing  inversely  as  the  arterial  resistance 
encountered  by  the  blood  in  its  progress  towards  the  veins. 
On  discontinuing  the  excitation,  the  heart  begins  to  beat 
again,  at  first  at  long  intervals,  subsequently  more  frequently, 
the  pressure  rapidly  increasing  until  (for  a  few  moments)  it 
exceeds  that  observed  before  excitation.  In  man,  the  trunk 
of  the  vagus  may  in  some  persons  be  excited  by  pressure,  and 
results  produced  which  correspond  with  those  of  electrical  ex- 
citation in  animals.  Prof*.  Czermak,  of  Leipsic,  is  able,  by 
making  pressure  at  the  proper  spot  on  the  right  side  of  the 
neck,  to  arrest  the  action  of  his  heart  for  a  few  moments.1 

76.  3.  Demonstration  of  the  Influence  of  certain 
Afferent  Nerves,  in  reflex  Relation  with  the  Inhibi- 
tory Nerves  contained  in  the  Vagus,  on  the  Heart. 
Bernstein's  Experiment. — The  inhibitory  heart  nerves 
contained  in  the  vagus  are  in  intimate  relation,  through  the 
heart  centre  in  the  medulla  oblongata,  with  certain  afferent 
fibres  contained  in  the  sympathetic  system ;  so  that  when 
these  fibres  are  excited,  the  same  effects  are  produced  as  if 
the  vagus  itself  was  directly  acted  upon.  This  may  be  shown 
in  the  frog  as  follows:  A  frog  is  secured  in  the  supine  position. 
The  pleuro-peritoneal  cavity  is  then  opened,  and  the  intestines 
and  other  viscera  are  removed,  great  care  being  taken  not  to 
injure  the  mesentery  or  the  vessels  and  nerves  which  it  con- 
tains. Nothing  now  remains  excepting  the  heart  resting  upon 
the  oesophagus.  By  carefulljr  dividing  the  double  layer  of 
serous  membrane  which  forms  the  lateral  wall  of  the  cisterna 
magna  on  both  sides  (see  Chap  II.),  the  ganglionic  chains 
(fig.  240)  are  brought  into  view  along  with  the  rami  com- 
mutneantes  b}r  which  the  ganglia  are  severally  connected  with 
the  anterior  roots  of  the  corresponding  spinal  nerves.  In  the 
thoracic  part  of  the  visceral  cavity  the  two  aortas  are  seen 
converging  downwards,  till  at  the  level  of  the  sixth  vertebra 
the}'  meet  to  form  one  trunk,  from  which  at  its  origin  the  me- 
senteric artery  is  given  off,  to  be  distributed  to  the  stomach 
and  intestines.  If  now  the  two  aortas  are  raised  near  their 
junctions,  with  the  point  of  the  forceps,  it  is  seen  that  one  of 

1  Populare  Vortrage,  p.  27. 


BY    DR.    BURDON-SANDERSON.  283 

the  ganglia  of  the  cord  sends  towards  the  mesenteric  arter}r  a 
branch  which  meets  with  its  fellow  from  the  corresponding 
ganglion  of  the  opposite  side,  to  form  a  plexus  of  nerves 
which  surrounds  the  artery;  and  that  from  or  through  this 
plexus  a  nerve  or  nerves  (nervi  mesenterici)  can  be  traced 
which  follow  the  vessel  towards  its  distribution.  It  is  in  these 
nerves  that  the  fibres  which  are  in  reflex  relation  with  the 
vagus  are  contained.  To  excite  them,  the  best  method  is  to 
raise  the  aortae  with  the  forceps  from  the  bodies  of  the  verte- 
brae, drawing  upwards  with  them  at  the  same  time  the  two 
ganglionic  cords;  then  to  divide  the  abdominal  aorta  and  the 
two  cords  at  the  level  of  the  seventh  or  eighth  vertebra,  sever- 
ing at  the  same  time  some  of  the  rami  communicantes  on 
either  side;  and  lastly,  to  place  the  two  aortse  and  the  cords 
which  accompany  them,  on  the  excitor  in  such  a  position  that 
the  two  ganglia  next  the  junction  are  in  contact  with  the 
electrodes.  On  opening  the  key,  the  heart  is  arrested  in  dias- 
tole, beginning  to  contract  again  rhythmically  as  before,  when 
the  excitation  is  discontinued.  To  demonstrate  that  the 
channels  by  which  stimulation  of  the  mesenteric  nerves  affects 
the  heart  are  the  vagus  nerves  and  their  centres  in  the  me- 
dulla oblongata,  the  experiment  must  be  thrice  repeated;  first, 
after  section  of  both  vagi ;  secondby,  after  destruction  of  the 
medulla  oblongata;  and  thirdly,  after  destruction  of  the  brain, 
the  medulla  remaining  intact.  In  the  first  and  second  cases 
the  effect  is  annulled,  in  the  third  it  is  unaltered.1 

77.  Reflex  Excitation  of  the  Vagus  of  the  Frog,  by 
Mechanical  Means:  Goltz's  Klopfversuch. — It  is  now 
many  years  since  it  was  discovered  by  Goltz  that  excitation  of 
the  ends  of  the  mesenteric  nerves  by  mechanical  means  produces 
the  same  effect  as  the  electrical  excitation  of  their  trunks.  To 
show  this,  a  frog  is  secured  on  its  back,  the  pleuro-peritoneal 
cavity  opened,  and  the  heart  exposed  as  before.  The  surface 
of  the  intestine  is  then  smartly  tapped.  After  a  few  moments 
the  heart  is  arrested  in  diastole.  If  the  ganglionic  cord  is  then 
divided  on  each  side  opposite  the  junction  of  the  two  aortae,  and 
the  experiment  repeated,  no  effect  is  produced.  Another  frog 
is  prepared  in  the  same  way,  with  the  exception  that  both  vagi 
are  divided.  On  repeating  the  tapping,  the  result  is  negative. 
The  same  thing  happens  if,  instead  of  dividing  the  vagi,  the 
cord  is  divided  immediately  below  the  medulla. 

78.  Reflex  Excitation  of  the  Vagus  in  Mammalia. — 
The  constant  action  of  the  inhibitory  heart  nerves  in  the  higher 
animals  is  dependent  on  the  constant  action  of  the  centripetal 
nerves  in  reflex  relation  with  them.     This  may  be  shown  as  fol- 

1  "  Unterrachtrogen  fiber  den  Mcchanismus  dee  regulatorischen  Herz- 
nerrensy stems."    Archiv  f.  Anat.  u.  Physiol.,  18G4,  p.  G14. 


284  CIRCULATION    OF   THE    BLOOD. 

lows :  Tn  a  rabbit,  the  trachea  is  connected  with  the  apparatus 
for  artificial  respiration,  and  the  vagi  arc  exposed  in  the  neck. 
Thereupon  the  spinal  cord  is  divided  immediately  below  the 
medulla  oblongata.  On  the  cessation  of  breathing,  artificial 
respiration  is  commenced.  The  cervical  sympathetica  are 
then  divided,  and  a  needle  is  inserted  in  the  heart.  A  succes- 
sion of  observations  of  the  frequency  of  the  heart's  action  is 
then  made,  and  both  vagi  are  divided.  No  acceleration  of  the 
pulse  rate  occurs. 

The  purpose  of  the  experiment  is  to  show  that  when  the  affer- 
ent sympathetic  nerves  which  are  known  to  be  in  reflex  relation 
with  the  vagus  heart  nerves  are  severed,  the  same  effect  is  pro- 
duced on  the  vagus  as  if  it  were  itself  divided.  There  is  no  way 
of  accomplishing  this  directly,  without  such  interference  with 
other  nerves  as  would  affect  the  heart,  and  thereby  render  the 
result  ambiguous.  The  most  complete  method  would  be  to 
remove  the  whole,  ganglionic  cord  on  both  sides.  Without 
reference  to  the  extreme  difficulty  of  such  an  operation,  it  is 
clear  that  it  would  involve  the  accelerator  nerves  (see  §  80), 
and  thereby  perhaps  produce  an  effect  the  opposite  of  that  which 
we  intended — a  slowing  instead  of  an  acceleration  of  the  pulse. 
So  also,  when  the  spinal  cord  is  divided  immediately  below  the 
medulla  oblongata,  the  effect  is  modified  not  only  by  the  de- 
struction of  the  accelerator  nerves,  but  b}r  the  general  paralysis 
of  the  vasomotor  system.  Consequently  no  answer  to  the 
question  is  to  be  obtained  by  direct  observation  of  the  changes 
which  are  produced  by  any  such  operation  in  the  rate  ofpulsa- 
tion  of  the  heart,  so  that  the  end  we  have  in  view  can  only  he 
accomplished  indirectly.  We  already  know  that  both  vagi  are 
in  constant  action,  i.  e..  that  the  heart  is  constantly  under  their 
inhibitory  control;  and  that  when  this  control  is  removed  by 
dividing  them,  the  frequency  of  the  pulse  increases.  It  is  ob- 
vious that  this  effect  can  only  be  witnessed  so  long  as  the  con- 
trol is  in  actual  exercise  ;  in  other  words,  that  if  the  vagi  are 
not  acting,  it  would  make  no  difference  as  regards  the  heart 
whether  they  are  divided  or  not.  The  consideration  of  this 
fact  suggests  the  method  which  is  employed  in  the  experiment 
above  described,  which  shows  that  in  an  animal  in  which  the 
spinal  cord  has  been  divided  below  the  medulla,  the  rate  of  the 
pulse  is  the  same  before  and  after  section  of  the  vagi. 

Bernstein  has  further  shown  that  the  same  thing  happens 
after  destruction  of  the  whole  ganglionic  cord,  or  of  the  cervi- 
cal part,  provided  that  the  spinal  cord  is  at  the  same  time 
severed  at  the  seventh  vertebra.  In  the  dog,  section  of  the 
cord  generally  diminishes  the  frequency  of  the  pulse.  There 
is  no  such  effect  in  the  rabbit.  The  difference  can  only  be  ex- 
plained by  supposing  that  in  the  former  the  activity  of  the 
accelerator  nerves  is  less,  as  compared  with  that  of  the  nerves 


BY    DR.    BURDON-SANDERSON".  285 

in  reflex  relation  with  the  vagus,  than  in  the  latter.  In  the 
frog,  section  of  the  sympathetic  at  the  level  of  the  junction  of 
the  aorta?  has  no  direct  effect  on  the  frequency  of  the  pulse,  for 
the  same  reason,  viz.,  that  in  this  animal  the  heart-beat  is  not 
quickened  by  section  of  the  vagi. 

The  influence  of  reflex  excitation  of  the  vagus  through  the 
fifth  nerve  may  be  easily  shown  in  the  rabbit  by  causing  the 
animal  to  smell  ammonia.  The  effect  is  immediate.  Accord- 
ing to  the  strength  of  the  ammonia,  the  heart  is  arrested  in 
diastole,  or  the  diastolic  intervals  are  lengthened.  The  inha- 
lation of  chloroform,  which  is  so  apt  to  be  fatal  to  rabbits,  stops 
the  heart  in  the  same  way.  When  sudden  death  occurs  in  a 
man  by  a  blow  on  the  epigastrium,  or  by  drinking  a  large 
quantit}'  of  cold  water,  the  heart  is  arrested  in  diastole  by  the 
agency  of  the  same  nerves  as  in  Goltz's  experiment. 

79.  Demonstration  of  the  Influence  of  Increase  or 
Diminution  of  the  Arterial  Pressure  on  the  Fre- 
quency of  the  Contractions  of  the  Heart. — The  pulse  is 
retarded  by  increase,  accelerated  by  diminution  of  arterial 
pressure.  That  these  effects  are  mainly  dependent  on  the  in- 
hibitory heart  nerves,  can  be  shown  in  the  rabbit  as  follows  : 
Ligatures  having  been  passed  round  the  vagus  nerve  on  each 
side,  and  a  needle  inserted  in  the  heart,  the  fingers  of  the  right 
hand  are  placed  under  the  animal's  back,  while  the  thumb  is 
firmly  pressed  upon  the  aorta,  the  beats  of  the  needle  having 
been  previously  counted.  On  making  pressure,  the  frequency 
of  the  contractions  of  the  heart  is  diminished,  and  this  effect 
continues  so  long  as  the  pressure  lasts. 

Both  vagi  are  now  divided  and  the  experiment  repeated. 
The  frequency  of  the  pulse  is  still  slightly  diminished,  but  the 
degree  of  diminution  is  not  to  be  compared  with  the  previous 
effect.  This  experiment  can  be  made  with  greater  exactitude 
by  applying  the  pressure  to  the  aorta  directly,  at  the  same 
time  connecting  the  carotid  artery  with  Fick's  kymograph. 
To  accomplish  the  first  of  these  objects,  the  abdominal  cavity 
is  opened  in  a  chloral ized  rabbit  in  exactly  the  same  way  as 
for  excitation  of  the  left  splanchnic  nerve.  It  is  then  easy  to 
place  the  thumb  directly  on  the  aorta  as  it  passes  between  the 
crura  of  the  diaphragm.  Tracings  are  thus  obtained  which 
show  that,  during  obstruction  of  the  aorta,  the  arterial  press- 
ure is  doubled,  or  even  trebled,  and  the  pulse  rate  much  di- 
minished, the  status  quo  being  re-established  when  the  thumb 
is  removed  from  the  aorta.  After  division  of  the  vagi,  the 
effect  as  regards  pressure  is  of  course  as  marked  as  before,  but 
there  is  scarcely  any  slowing  of  the  pulse. 

The  fact  that  the  effect  of  aortic  obstruction  in  diminishing 
the  frequency  of  the  pulse  is  so  markedly  weakened  by  section 
of  both  vagi,  shows  that  these  nerves  bear  a  large  part  in  its 


286  CIRCULATION    OF    THE    BLOOD. 

production,  and  therefore  that  the  relation  between  cause  and 
consequence  is  in  this  case  not  dependent  on  the  lengthening 
of  the  systole  by  resistance,  as  supposed  hy  Marey.  The 
question,  however,  remains,  whether  the  mechanical  explana- 
tion may  not  be  accepted  as  regards  the  remainder  of  effect 
which  is  observed  after  the  vagi  are  divided.  There  are  two 
reasons  why  this  is  not  possible.  One  is,  that  here,  as  in  other 
cases  when  the  pulse  rate  is  retarded,  the  retardation  does  not 
signify  that  the  systole  is  lengthened,  but  that  the  diastolic 
intervals  are  more  protracted.  The  other  reason  is,  that  even 
after  section  of  the  vagi,  the  retardation  of  pulse  produced  by 
increased  arterial  pressure  is  postponed,  whereas  if  it  were 
merely  mechanical  it  would  certainly  be  immediate.  We  must 
therefore  turn  to  the  nervous  system  for  its  explanation — 
either  to  some  influence  exercised  on  the  heart  by  means  of 
accelerator  nerves,  which  after  section  of  the  vagi  are  the  only 
channel  by  which  the  heart  is  in  communication  with  the  cere- 
brospinal centres,  or  to  excitation  of  the  inhibitory  nerves  in 
the  heart  itself.  Considering  that  in  the  frog  the  same  effects 
are  produced  by  exciting  the  ganglion  of  the  vagus  in  the  cut- 
out heart  as  by  exciting  the  vagus  itself,  and  that  we  have 
no  reason  to  believe  that  increased  pressure  produces  any 
paralyzing  influence  on  the  accelerators,  we  need  have  little 
hesitation  in  concluding  that  the  effect  of  increased  blood- 
pressure  in  retarding  the  heart's  rl^-thm  is  exercised  entirely 
through  the  inhibitory  heart-nerves  ;  and  that  it  is  due  princi- 
pally to  the  increased  supply  of  blood  to  the  intra-cranial  vagus 
centre — i.  e.,  to  the  medulla  oblongata,  but  partly  also  to  the 
influence  of  the  increased  endocardial  pressure  on  the  vagus 
ends  in  the  heart  itself. 

80.  Demonstration  of  the  Functions  of  the  Accele- 
rator Nerves. — It  has  been  already  seen  that  when,  after 
severance  of  the  spinal  cord  just  below  the  medulla  oblongata, 
the  organ  is  excited  electrically  below  the  section,  two  effects 
are  produced — the  arterial  pressure,  reduced  by  the  section,  is 
enormously  increased,  and  the  heart  beats  much  more  fre- 
quently. Bczold  thought  that  both  of  these  effects  were  due 
to  the  direct  action  of  the  spinal  cord  on  the  heart.  Ludwig 
and  Thiry  showed  that,  as  regards  arterial  pressure,  this  was  a 
mistake.  They  also  showed  that  the  acceleration  of  the  pulse 
was  in  part  a  secondary  effect  of  the  increased  resistance  to  the 
flow  of  blood  ;  for  they  found  that  even  after  the  complete 
severance  of  all  nervous  communication  between  the  heart  and 
the  spinal  cord,  the  pulse  became  markedly  more  frequent  on 
excitation  of  the  cord.  Hence  Ludwig  was  led  to  doubt 
whether,  after  all,  the  central  nervous  system  exercised  any 
direct  accelerative  influence  on  the  heart.  We  now  know  that 
while  v.  Bezold  was  wrong  in  believing  that  the  spinal  nerves 


BY    DR.    BURDON-SANDERSON.  287 

have  any  power  of  augmenting  the  energy  of  the  heart's  con- 
tractions, or  of  causing  it  to  do  more  work  in  a  given  time, 
there  are  certain  nerves  by  which  the  distribution  of  its  efforts 
in  time  may  be  modified  in  the  direction  of  greater  frequency. 
By  the  following  experiment  it  can  be  shown  that  the  accele- 
ration of  pulse  which  is  produced  b}'  electrical  excitation  of 
the  severed  spinal  cord  is  independent  of  increase  of  arterial 
pressure. 

In  a  curarized  rabbit  in  which  respiration  is  maintained  arti- 
ficially, the  spinal  cord  is  severed  from  the  medulla,  and  the 
vagi,  sympathetica,  and  depressors  are  divided.  The  arterial 
pressure  of  course  sinks  to  about  an  inch  of  mercury,  and  the 
pulse  becomes  slower.  The  cord  is  then  excited  electrically. 
The  pressure  rises  at  once  to  four  or  five  inches,  the  rate  of 
the  heart's  contractions  also  increasing,  but  not  in  proportion 
to  the  rise  of  pressure.  As  soon  as  the  effects  of  stimulation 
have  subsided,  and  the  circulation  has  had  time  to  resume  its 
former  condition,  both  splanchnics  are  divided,  in  consequence 
of  which  the  pressure  again  sinks  a  few  millimetres.  The  ke\r 
is  opened  :  again  we  have  acceleration  of  the  pulse,  but  this 
time,  the  verm  pressores  having  been  divided,  the  excitation 
produces  hardly  an}r  effect  on  the  arterial  tension.  The  results 
of  one  of  Ludwig's  experiments  are  as  follows  :  After  section 
of  the  depressors,  vagi,  and  sympathetics,  arterial  pressure  60 
millimetres,  pulsations  in  15  seconds,  52  ;  after  section  of  cord, 
arterial  pressure  20  millimetres,  pulsations  45  ;  during  excita- 
tion of  cord,  arterial  pressure  80  millimetres,  pulsations  61; 
after  section  of  splanchnics,  arterial  pressure  10  millimetres, 
pulsations  27;  during  excitation  of  medulla,  arterial  pressure 
12  millimetres,  pulsations  42. 

81.  Proof  that  the  Inferior  Cervical  Ganglion  is 
the  Channel  by  •which  the  Direct  Influence  of  the 
Spinal  Cord  on  the  Heart  is  exercised. — Before  pro- 
ceeding to  describe  the  experiments  by  which  this  is  shown, 
it  will  be  necessary  to  give  an  account  of  the  anatomical  rela- 
tions of  the  lowest  cervical  ganglion  in  the  rabbit  and  dog. 
It  is  obvious,  from  what  we  know  of  the  anatomy  of  the 
cardiac  nerves  as  well  in  man  as  in  the  lower  animals,  that, 
with  the  exclusion  of  the  vagus,  the  only  channels  by  which 
the  spinal  cord  can  influence  the  heart  directly  are  the  rami 
communicantes,  by  which  it  is  united  with  the  ganglia.  By 
experiment  we  learn  that  the  communicating  filaments  by 
which  the  accelerating  influence  of  the  cerebro-spinal  centres 
is  transmitted,  are  those  which  enter  the  inferior  cervical 
ganglion. 

In  the  rabbit,  the  trunk  of  the  cervical  sympathetic  ends  at 
the  root,  of  the  neck,  in  the  inferior  ganglion.  This  ganglion 
lies  deeply  on  the  surface  of  the  muscles  which  cover  the  spinal 


2S8  CIRCULATION    OF   THE    BLOOD. 

column  (longus  colli),  and  consequently  to  the  inner  side  of 
the  tendinous  origins  of  the  scalenus  milieus  from  the  trans- 
verse processes.  It  has  the  oesophagus  on  its  inner  .side,  the 
vertebral  artery  on  its  outer,  and  lies  behind  the  carotid  artery 
and  internal  jugular  vein.  The  following  are  the  best  guides 
to  its  discovery:  Superficially,  the  junction  of  the  external 
jugular  vein  and  subclavian  vein  to  form  the  vena  innominata, 
in  the  angle  between  which  vessels  the  phrenic  nerve  appears 
lying  on  the  scalenus  anticus  ;  more  deeply,  the  origins  of  the 
scalenus  anticus,  from  the  two  last  cervical  transverse  pro- 
cesses; and  particularly  the  vertebral  artery  where  it  passes 
to  the  inside  of  these  insertions,  to  enter  the  foramen  trans- 
veraarmm  of  the  sixth  cervical  vertebra.  The  upper  end  of 
the  ganglion  is  to  be  found  close  to  the  artery  on  its  inner 
side.  The  ganglion  receives  from  above,  in  addition  to  the 
sympathetic  trunk,  communicating  branches  from  the  brachial 
plexus  and  from  the  vagus,  and  a  branch  (the  so-called  radix 
brevis)  which  accompanies  the  vertebral  artery.  Downwards, 
the  ganglion  sends  (besides  those  leading  to  the  first  thoracic 
ganglion)  branches  wdiich  go  towards  the  heart.  One  of  the 
most  internal  of  these  is  the  continuation  of  the  depressor 
nerve,  to  be  hereafter  mentioned,  which  rather  passes  by  the 
ganglion  than  springs  out  of  it,  and  looses  itself  in  the  plexus 
of  nerves  between  the  aorta  and  pulmonary  artery.  The  com- 
munication between  the  lower  cervical  and  the  first  thoracic 
ganglion  takes  place  by  two  nerves,  one  of  wdiich  passes  in 
front  of,  the  other  behind,  the  subclavian  artery,  before  that 
arteiy  gives  off  the  vertebral.  The  accelerator  fibres  enter 
the  ganglion  by  the  vertebral  nerve,  and  thence  find  their  way 
to  the  heart  through  the  cardiac  plexus  already  mentioned. 
(See  explanation  of  fig.  241.) 

In  the  dog,  the  arrangement  of  the  accelerator  nerves  is 
somewhat  different.  In  this  animal,  as  in  the  rabbit,  the 
lower  cervical  ganglion  lies  on  the  longua  colli  immediately  to 
the  inner  side  of  the  vertebral  artery,  and  above  the  subclavian. 
It  is  connected  with  the  first  thoracic  ganglion  by  two  twigs, 
one  of  wdiich  passes  behind  the  subclavian  and  vertebral  arte- 
ries, the  other  in  front  of  them.  Of  its  cardiac  branches,  of 
which  three  have  been  distinguished  by  Cyon,  the  most  im- 
portant accompanies  the  recurrent  nerve  until  that  nerve 
bends  upwards  to  its  distribution,  and  then  follows  the  sub- 
clavian or  innominate  artery  to  gain  the  cardiac  plexus.  From 
above,  the  ganglion  receives,  first,  the  combined  trunk  of  the 
vagus  and  sympathetic,  which  here  separate  from  each  other, 
the  former  continuing  its  course  into  the  thorax  ;  and  secondly, 
two  branches  corresponding  to  those  described  in  the  rabbit. 
The  accelerator  fibres  are  very  variously  distributed  among 
these  several  branches,  sometimes  finding  their  way  to  the 


BY    DR.    BURDON-SANDERSON.  289 

heart  from  the  inferior  cervical  ganglion  along  the  vagus,  or 
the  recurrent,  but  most  frequently  by  the  cardiac  branch 
above  described.  For  further  details,  see  the  explanation  of 
fig.  242. 

Before  entering  on  an}'  experimental  inquiry  relating  to  the 
accelerator  nerves,  it  is  absolutely  necessary  to  make  several 
dissections.  The  mode  of  experiment  is  as  follows:  In  a  cu- 
rarized  rabbit  in  which  artificial  respiration  is  maintained  in 
the  usual  way,  an  incision  is  made  in  the  middle  line  extending 
from  the  upper  third  of  the  sternum  to  the  upper  end  of  the 
trachea.  The  external  jugular  vein  of  one  side  is  then  brought 
into  view,  tied  in  two  places,  and  divided  between  the  liga- 
tures. The  steruo-mastoid  muscle  is  also  divided  between 
ligatures :  a  strong,  threaded  aneurism  needle  is  thrust  under 
the  sterno-clavicular  ligament  and  the  upper  fibres  of  the 
pectoral  muscles  ;  these,  with  the  ligament,  are  divided  be- 
tween ligatures,  and  the  cut  ends  drawn  aside.  By  this  pro- 
ceeding, the  carotid  artery,  the  internal  jugular  vein,  and  the 
subclavian  vein,  are  brought  into  view.  These  veins  and  the 
vena  anonyma  are  tied  and  divided  in  the  manner  already  in- 
dicated, and  any  other  vessels  which  come  in  the  way  are  se- 
cured. A  simpler  and  more  rapid  mode  of  performing  the 
operation  is  the  following :  The  superficial  parts  having  been 
exposed  by  two  lines  of  incision,  one  of  which  is  in  the  middle 
line,  while  the  other  extends  from  it  on  either  side  in  the  di- 
rection of  the  sterno-clavicular  ligament,  and  the  jugular  vein 
having  been  divided  between  ligatures,  the  next  step  is  to  find 
the  pneurnogastric  nerve  at  the  upper  part  of  the  wound,  and 
free  it  from  the  surrounding  tissues.  This  done,  a  blunt  aneu- 
rism needle  is  threaded  and  passed  carefully,  with  its  convexity 
backwards,  along  the  course  of  the  nerve,  between  it  and  the 
carotid  artery.  Its  point  is  then  made  to  penetrate  the  sheath 
and  fascia  immediately  above  the  long,  cord-like,  sterno-clavi- 
cular ligament.  The  thread  is  then  severed,  and  the  ends 
having  been  drawn  out  to  a  sufficient  length,  the  two  ligatures 
are  tightened,  the  one  inside  and  the  other  outside  of  the 
aneurism  needle,  after  which  the  whole  of  the  tissues  which 
are  tied  off  between  the  ligatures,  including  the  great  veins, 
may  be  raised  on  the  needle  and  divided.  The  needle,  which 
has  been  carefully  kept  in  its  place,  is  now  again  threaded, 
and  its  point  pushed  downwards  under  the  edge  of  the  pectoral 
muscles,  as  far  as  the  upper  surface  of  the  first  rib.  The  point 
is  then  pushed  outwards  and  forwards  through  the  muscles, 
the  thread  is  again  severed,  and  the  muscles  are  divided  be- 
tween the  two  ligatures  in  the  manner  already  described.  By 
this  proceeding  a  deep  hollow  (see  fig.  243)  is  exposed,  in 
which,  among  other  important  parts,  the  ganglion  inferiics 
lies,  covered  by  a  layer  of  fascia.  This  hollow  is  bounded 
19 


290  CIRCULATION   OF   THE   BLOOD. 

below  by  the  crescentic  upper  border  of  the  first  rib,  behind 
and  to  the  outside  by  the  scalenus  anticus,  and  to  the  inside  by 
the  trachea  and  (on  the  right  side)  by  the  oesophagus.  In  the 
depth  of  the  hollow,  to  the  outside,  lies  the  subclavian  artery 
on  its  way  to  cross  outwards  over  the  first  rib  :  the  vertebral 
artery  springs  from  it  just  as  it  is  about  to  leave  the  hollow 
space.  This  vessel  is  the  guide  to  the  ganglion  which  lies  on 
its  inner  side  concealed  in  a  good  deal  of  cellular  tissue.  To 
find  it,  the  most  certain  method  is  to  seek  for  the  trunk  of  the 
sympathetic  in  the  upper  part  of  the  space  where  it  lies  con- 
cealed behind  the  carotid  artery,  and  then  to  trace  it  down  to 
the  ganglion.  All  this  having  been  accomplished  without 
bleeding,  there  is  no  difficulty  in  passing  a  ligature  round  the 
ganglion,  so  that  at  any  desired  moment  it  may  be  extirpated. 
The  same  operation  is  then  performed  on  the  opposite  side  of 
the  body.  Both  ganglia  having  been  thus  prepared  with  as 
little  loss  of  time  as  possible,  the  sympathetic  and  vagus  are 
divided  (so  as  completelj'  to  sever  the  nervous  connection  be- 
tween the  heart  and  the  central  nervous  system),  and  one  of 
the  carotids  is  connected  with  the  kymograph. 

The  medulla  oblongata  is  then  divided,  and  comparative 
observations  are  made,  in  the  manner  already  directed,  as  to 
the  effect  of  excitation  of  the  peripheral  end  of  the  spinal 
cord  on  the  arterial  pressure,  and  on  the  frequency  of  the  pulse 
before  and  after  extirpation  of  both  ganglia.  In  the  one  case, 
the  rise  of  pressure  is  attended  with  acceleration  ;  in  the  other, 
the  frequency  of  the  contractions  of  the  heart  remains  un- 
altered. This  result  proves,  first,  that  the  accelerative  influ- 
ence of  the  cordon  the  heart  is  conveyed  by  nerves  which  pass 
through  the  ganglia;  and  secondly,  that  these  nerves  are  not 
in  constant  action.  Although  the  cord,  when  excited,  acts 
throughout  by  means  of  them,  their  destruction  produces  no 
effect  on  the  heart  when  the  cord  is  quiescent.  To  complete 
the  proof  that  the  nerves  which  pass  to  the  heart  from  the 
sympathetic  trunk,  and  particularly  those  which  spring  from 
the  ganglion,  are  concerned  in  shortening  the  diastolic  inter- 
vals, direct  observations  are  necessary.  Such  observations 
were  first  made  by  the  brothers  Cyon,  who  found  that  both  in 
the  dog  and  rabbit  most  of  the  accelerator  fibres  reach  the 
ganglion  by  the  nerve  which  accompanies  the  vertebral  artery. 
In  both  animals,  but  especially  in  the  dog,  as  has  been  already 
stated,  the  path  followed  by  these  fibres  from  the  ganglion  to 
the  heart  varies  considerably  in  different  individuals.  The 
experiments  by  which  these  facts  have  been  established  are 
among  the  most  difficult  in  physiology,  and  consequently  the 
description  of  them  lies  beyond  the  scope  of  this  work. 

From  the  preceding  experiments  and  observations,  we  learn 
that  it  is  the  function  of  the  accelerator  nerves  to  shorten  the 


BY   DR.    BURDON-S ANDERSON.  291 

diastolic  interval,  and  thus,  indirect^,  to  render  the  individual 
contractions  of  the  heart  feeble  and  less  effectual.  How  they 
act,  and  what  is  their  anatomical  and  physiological  relation 
either  to  the  ganglion  cells,  or  to  the  vagus  of  which  they  are 
the  antagonists,  it  is  not  at  present  possible  to  explain.  As 
has  been  already  stated,  the  heart  of  the  frog  does  not  receive 
any  accelerator  nerves.  From  the  following  experiment,  how- 
ever, it  appears  that  the  vagus  nerves  in  that  animal  contain 
accelerator  fibres.  To  demonstrate  this,  the  animal  must  be 
placed  under  the  influence  of  nicotin,  which  alkaloid,  as  lately 
shown  by  Schmiedeberg,  possesses  the  power  of  paralyzing  the 
terminations  of  the  inhibitory  fibres  contained  in  the  trunk  of 
the  vagus,  without  affecting  the  intrinsic  inhibitory  ganglia  of 
the  heart.  If  in  a  frog,  into  which  about  a  thirtieth  of  a  grain 
of  nicotin  has  been  injected,  one  vagus  nerve  is  excited,  the 
excitation,  instead  of  arresting  the  heart  in  diastole,  or  dimin- 
ishing its  frequency,  accelerates  its  contractions.  And  if, 
instead  of  injecting  the  solution  under  the  skin,  the  heart  is 
prepared  after  Dr.  Coats's  method,  supplied  with  serum  con- 
taining nicotin,  and  connected  with  the  kymograph,  and 
observed  before,  during  and  after  excitation  of  the  vagus, 
tracings  are  obtained  which  show  that  the  frequency  of  the 
heart-beats  is  increased  sixty  per  cent.;  that  the  acceleration 
commences  about  four  seconds  after  the  opening  of  the  key, 
and  lasts  about  a  minute  and  a  half  after  the  cessation  of  the 
excitation;  and  that  it  is  due  to  shortening,  or  rather  annull- 
ing, of  the  diastole,  each  systole  following  immediately  on  the 
close  of  the  preceding  one  (see  fig.  244). 

82.  Demonstration  of  the  Functions  of  the  Depres- 
sor Nerve. — In  the  rabbit  as  well  as  in  the  cat,  a  cardiac 
branch  separates  itself  from  the  vagus  at  the  level  of  the  thy- 
roid cartilage,  high  in  the  neck,  and  ends  in  the  inferior  cervical 
ganglion.  In  the  rabbit,  the  nerve  commonly  originates  in 
two  roots,  one  of  which  springs  from  the  superior  lar}'ngeal, 
the  other  from  the  vagus  itself,  near  the  point  at  which  the 
laryngeal  leaves  it ;  but  very  often  it  is  derived  exclusively 
from  the  superior  laryngeal.  In  its  course  towards  the  inferior 
cervical  ganglion,  it  is  close  to  the  carotid  artery,  and  still 
closer  to  the  sympathetic  trunk,  from  which  it  is  distinguished 
by  its  smaller  size  and  whiter  aspect.  From  the  ganglion  the 
fibres  of  the  depressor  are  continued  downwards,  forming  the 
two  most  internal  of  the  filaments  which  in  the  rabbit  pass  be- 
tween it  and  the  heart.  They  can  be  traced  to  the  connective 
tissue  between  the  origin  of  the  aorta  and  pulmonary  artery. 
The  depressor  contains  centripetal  fibres,  the  function  of  which 
is  to  diminish  the  activity  of  the  vasomotor  centre,  and  thereby 
diminish  the  arterial  pressure. 

A   rabbit  is  chloralized  ;  one  carotid  is  connected  with  the 


202  CIRCULATION    OF    THE    BLOOD. 

kymograph,  and  the  vagus  of  the  same  side  divided  opposite 
the  thyroid  cartilage.  The  depressor  is  isolated,  and  a  loop 
of  thread  passed  round  it.  An  observation  is  then  taken  of 
the  arterial  pressure  and  pulse  rate,  after  which  the  depressor 
is  divided.  There  is  no  alteration  either  in  the  height  of  the 
mercurial  column,  or  in  the  number  of  pulsations  per  ten 
seconds.  On  exciting  the  peripheral  end,  there  is  still  no 
effect ;  but  on  exciting  the  central  end  the  pressure  sinks  to 
about  two-thirds  of  its  previous  height,  and  the  pulse  often  be- 
comes slower.  On  discontinuing  the  excitation,  the  status  quo 
is  gradually  restored. 

The  results  of  such  an  experiment  are  shown  in  the  tracing 
(fig.  245).  It  i3  seen  that  the  excitation  produces  no  change 
whatever  either  in  the  character  or  frequency  of  the  pulsations, 
the  only  effect  produced  being  diminution  of  pressure.  In  other 
instances  there  is  perceptible  slowing,  but  the  variations  of  the 
two  effects  are  never  parallel.  In  the  observation  recorded  in 
the  tracing,  the  vagus  of  the  side  opposite  to  that  on  which  the 
depressor  was  excited,  was  left  intact ;  consequently  the  heart 
was  still  partly  under  the  control  of  the  intracranial  inhibitory 
centre.  Notwithstanding  this,  the  slowing  was  not  appreci- 
able. When  it  does  occur,  it  must  be  attributed,  without  doubt, 
to  reflex  excitation  of  the  inhibitory  heart  centre,  the  effect  of 
which  is  conveyed  to  the  heart  by  the  undivided  vagus. 

The  diminution  of  the  arterial  pressure  cannot  be  referred 
to  any  direct  influence  exercised  by  excitation  of  the  depressor 
on  the  heart,  but  to  diminution  of  the  resistance  in  the  arterial 
system  ;  i.  e.,  to  relaxation  of  the  minute  arteries.  This  may 
be  shown  in  the  same  animal  which  is  used  for  the  preceding 
experiment,  if  the  left  splanchnic  is  divided  (see  §  56)  and  the 
depressor  excited  as  before.  The  mercurial  column,  which  has 
already  fallen,  sa3r,  to  two-thirds  of  its  former  height,  is  further 
depressed  during  excitation  ;  but  the  amount  of  sinking  is 
much  less  than  it  would  have  been  if  the  splanchnic  had  not 
been  divided. 

The  same  conclusion  is  confirmed  by  two  other  observations, 
viz.,  (1)  that  if  the  aorta  is  obstructed  so  as  to  raise  the  arterial 
pressure  and  conceal  any  changes  in  the  state  of  contraction 
of  the  abdominal  vessels,  the  effect  of  the  excitation  of  the  de- 
pressor is  imperceptible  :  and  (2)  that  if  the  abdominal  organs 
are  exposed  and  inspected  during  excitation  of  the  depressor, 
they  are  seen,  according  to  Cyon,  to  become  congested.  The 
effect  is  most  perceptible  in  the  kidneys,  which  (if  care  is  taken 
to  avoid  the  previous  occurrence  of  congestion  from  exposure 
or  other  conditions)  change  color  from  pale  to  red,  and  back 
again,  as  the  induced  current  is  closed  or  opened. 


BY   DR.    BURDON-SANDERSON.  293 

SUPPLEMENT. 

Absorption  by  the  Veins  and  Lymphatics. 

Under  this  head,  certain  experiments  will  be  referred  to  re- 
lating to  the  mode  in  which  soluble  and  insoluble  substances 
find  their  wa}-  into  the  vascular  system  from  the  tissues.  This 
kind  of  absorption  may  be  termed,  in  order  to  distinguish  it 
from  that  which  takes  place  at  the  cutaneous  and  mucous  sur- 
faces, internal  absorption.  The  other  kind  will  be  dealt  with 
in  succeeding  Chapters. 

It  is  obvious,  so  far  as  relates  to  the  bloodvessels,  that  con- 
sidering that  the  whole  vascular  system,  with  the  exception  of 
that  of  the  spleen,  the  medulla  of  bone,  and  some  other  smaller 
tissues,  is  lined  with  a  continuous  membrane,  no  substance  can 
enter  them  excepting  in  a  state  of  solution,  and  consequently 
that  the  process  of  venous  absorption  is  one  of  filtration  or 
diffusion;  and  that,  of  these  two,  the  former  is  excluded  by  the 
fact  that  the  pressure  inside  of  the  vascular  system  is  every- 
where greater  than  the  pressure  outside.  As  regards  the  lym- 
phatic  system,  on  the  other  hand,  the  anatomical  facts  des- 
cribed in  Chap.  VIII.  will  show  that  there  is  no  obstacle  to  the 
entry  of  solid  substances,  provided  that  they  are  in  a  state  of 
extremely  fine  division ;  so  that  we  are  led  to  infer  that, 
whereas  it  is  the  function  of  the  bloodvessels  to  absorb  sub- 
stances which  are  soluble  and  diffusible,  those  which  are  inca- 
pable of  diffusion  are  taken  up  by  the  lymphatics. 

From  experiments  we  learn,  not  merely  that  this  inference 
is  correct,  but  that  the  process  of  absorption  from  the  tissues 
by  the  veins  is,  like  the  analogous  process  of  secretion  (Chap. 
XXXVI.),  dependent  on  the  nervous  system. 

83.  Proof  that  Solid  Matters  in  a  State  of  Extremely- 
Fine  Division  are  Absorbed  from  the  Tissues  by  the 
Lymphatics. — In  Chapter  VIII.  it  has  been  shown  that, 
without  reference  to  the  origin  of  the  lacteals  from  the  mucous 
membrane  of  the  intestine,  or  to  the  stomata,  by  which  the 
lymphatic  system  communicates  with  the  serous  cavities,  the 
absorbent  S3rstem  originates  from  those  forms  of  interstitial 
tissue  which  for  the  present  we  designate  lymphatic,  the  char- 
acteristic of  which  is  that  they  consist  of  ground  substance, 
riddled  in  all  directions  by  cavities  containing  protoplasm 
masses — z.  «.,  cells,  these  cavities  being  in  communication  with 
each  other,  as  well  as  with  the  lymphatic  capillaries,  by  a  net- 
work of  channels  (lymphatic  canaliculi  or  Saftkanalchen). 
The  distribution  in  the  body  of  interstitial  tissue  having  these 
characters  has  not  yet  been  sufficiently  investigated  ;  for  it  is 
only  during  the  last  year  or  two  tWat  its  anatomical  relations 
have  been   more  or  less  completely  made  out.     We  already 


294  CIRCUF.ATION    OF    THE    BLOOD. 

know,  however,  that  it  is  to  be  found  almost  everywhere,  par- 
ticularly in  the  tunica  adventitia  of  bloodvessels,  underneath 
the  endothelial  lining  of  serous  cavities,  and  of  the  vascular 
system,  and  on  the  surface  and  in  the  inter-fascicular  splits  of 
tendons  and  aponeuroses  ;  and  that,  wherever  it  occurs,  it  is  in 
anatomical  relation  with  lymphatic  capillaries.  The  proof 
that  the  absorption  of  solid  matters  in  line  division  takes  place 
mechanically,  has  already  been  given  in  Chapter  VIII.,  where 
it  is  shown  that  the  lymphatics  leading  from  the  peritonaeum 
can  be  filled  with  Prussian  blue  or  other  coloring  matters  in 
suspension,  by  injecting'the  liquid  charged  with  them  into 
the  peritomeal  cavity;  and  that  if  the  mechanical  conditions 
are  favorable,  the  injection  takes  place  in  the  same  manner  in 
the  dead  body  as  in  the  living.  It  has  also  been  shown  in  the 
same  Chapter,  that  in  order  to  obtain  good  anatomical  pre- 
parations of  lymphatic  capillaries,  the  best  method  is  that 
there  described  as  the  method  of  puncture,  the  reason  being 
that,  wherever  these  vessels  are  abundant,  they  are  in  open 
communication  with  the  canaliculi,  and,  consequently,  that  it 
is  impossible  to  introduce  the  point  of  a  syringe  into  the  tissue 
between  them  without  penetrating  many  of  these  cavities. 
This  may  be  instructively  shown  as  follows. 

84.  Method  of  Showing  the  Mode  of  Entry  of  Col- 
ored Liquids  into  the  Lymphatic  Vessels. — The  best 
tissue  for  the  purpose  is  the  mucous  membrane  of  the  larynx 
and  trachea  ;  those  of  an  ox  or  sheep  may  be  used.  An  ordi- 
nary subcutaneous  syringe,  with  as  fine  a  point  as  possible,  is 
charged  with  solution  of  alkanet  in  spirits  of  turpentine.  The 
point  is  then  inserted  horizontally  into  the  mucous  membrane, 
at  some  part  where  it  rests  upon  cartilage.  A  drop  of  the 
liquid  is  then  pushed  out  into  the  tissue  as  slowly  as  possible. 
If  the  operation  is  successful,  it  at  once  fills  the  lymphatic  net- 
work, the  character  of  the  result  varying  according  as  the 
point  of  the  S3rringe  has  entered  the  submucosa  or  has  not 
penetrated  beyond  the  mucosa.  That  the  liquid  progresses 
along  the  vessels  by  capillarity  is  learnt  by  observing  that  the 
injection  continues  to  spread  long  after  all  pressure  from  the 
syringe  has  ceased.  The  alkanet  solution  is  employed  in  this 
and  similar  experiments,  because  it  is  quite  incapable  of  pass- 
ing through  organic  membranes,  is  immiscible  with  water,  and 
enters  capillary  channels  with  extraordinary  facilit}'. 

The  further  progress  of  liquids  along  the  lymphatics  towards 
the  venous  system  is  due  partly  to  capillarit}-,  partly  to  the 
fact  that  the  lymphatics  pass  through  spaces  in  which  the 
pressure  is  less  than  that  in  which  their  capillaries  originate, 
and  partly  to  the  variations  of  pressure  due  to  muscular  action, 
to  which  they  are  subjected,.     That  in  certain  parts  of  the  body 


BY    DR.    BURDON-SANDERSON.  295 

the  lymphatic  trunks  are  subjected  to  a  less  pressure  than  their 
absorbing  orifices,  does  not  need  special  experimental  proof. 
Thus,  for  example,  it  is  certain  that  the  h/niphatics  of  the  peri- 
toneum enter  the  thorax,  i.  e.,  pass  from  a  cavity  where  the 
pressure  is  usually  greater,  to  another  where  it  is  much  less 
than  that  of  the  atmosphere.  The  influence  of  muscular  move- 
ments admits  of  being  demonstrated  by  the  following  experi- 
ment, which  at  the  same  time  affords  a  striking  confirmation 
of  the  evidence  already  given  as  to  the  mechanical  nature  of 
lymphatic  absorption. 

In  a  large  dog,  which  has  been  just  killed  by  opening  one 
carotid,  the  skin,  costal  cartilages,  and  muscles  of  the  flank  are 
severed  by  a  transverse  incision,  which  extends  from  the  ensi- 
form  cartilage  as  far  as  the  middle  line  on  either  side.  The 
wall  of  the  abdomen  is  then  split  vertically  in  the  linea  alba, 
and  the  diaphragm  cut  away  from  the  ribs.  The  bladder  hav- 
ing been  squeezed  empty,  two  ligatures  are  tightened  round 
the  rectum,  which  is  divided  between  them.  Ligatures  must 
now  be  placed  round  the  cardia,  the  hepatic  vessels,  and  duct, 
and  the  mesentery,  so  as  to  remove  the  stomach  and  intestines 
en  manse  without  bleeding.  This  having  been  accomplished, 
the  vena  cava  is  tied  above  and  below  the  liver,  and  that  organ 
removed,  after  which  the  body  is  bisected  by  sawing  through 
the  eighth  vertebra,  and  completing  the  division  of  the  soft 
parts.  Finally,  a  glass  canula,  fitted  with  a  flexible  tube 
guarded  by  a  clip,  is  inserted  in  the  thoracic  duct  and  secured 
with  a  ligature. 

If  now  the  spinal  column  is  fixed  near  the  edge  of  the  table, 
and  the  lower  limbs  alternately  flexed  and  extended  by  an  as- 
sistant, the  lymph  flows  freely  and  may  be  received  in  a  test 
tube.  If  the  passive  movement  is  discontinued  and  then  re- 
sumed from  time  to  time,  the  quantity  of  lymph  collected  is  very 
considerable,  so  that  it  is  easy  to  fill  several  test  tubes  ;  but 
none  is  discharged  during  the  intervals  of  cessation.  The  lymph 
which  is  collected  at  first,  resembles  ordinary  lymph  both  in 
its  microscopical  characters  and  in  its  composition.  It  is  ob- 
vious that  it  is  the  liquid  which  at  the  moment  of  death  occu- 
pied the  canaliculi  of  the  tissues  from  which  it  is  gathered. 
The  course  taken  by  the  lymph  stream  can  be  further  demon- 
strated in  the  same  preparation,  by  introducing  solution  of 
alkanet,  by  puncture,  into  the  intertendinous  splits  of  the 
lower  part  of  the  fascia  lata.  If  a  sufficiently  fine  syringe  is 
used,  it  is  easy  to  produce  in  this  way  a  satisfactory  injection, 
first,  of  the  tymphatic  capillaries  contained  in  the  splits  them- 
selves, and  secondly  (if  the  passive  movements  are  continued), 
of  the  rich  net-work  of  lymphatics  which  exists  in  the  "  cellular 
membrane"   which  covers  the  aponeurosis    on   its  cutaneous 


29G  CIRCULATION    OF    THE    BLOOD. 

aspect.1  Soon  the  discharge  from  the  thoracic  duct  is  reddened 
by  the  alkanet.  It  has  been  shown  by  Ludwig  that  in  the  ex- 
tremities, the  tendons  and  aponeuroses  are  the  special  seat  of 
the  net-works  of  capillaries  by  which  the  lymphatics  commence, 
and  that  they  have  here  an  arrangement  similar  to  that  observed 
in  the  central  tendon  of  the  diaphragm.  The  experiment  proves 
that  even  passive  movements  of  the  limbs,  by  alternately  tight- 
ening and  relaxing  these  structures,  press  forwards  the  lymph 
stream.  The  influence  of  active  movements  must  be  much 
greater. 

85.  Internal  Absorption  by  the  Veins. — The  propo- 
sition stated  at  the  beginning  of  the  section,  that  substances 
in  solution  enter  the  capillaries  from  the  tissues  by  a  process 
of  absorption,  which  is  under  the  immediate  control  of  the 
nervous  system,  may  be  strikingly  illustrated  as  follows  : — 

Two  frogs  having  been  slightly  curarized  are  prepared  thus: 
The  heart  having  been  exposed  lege  artis ;  a  small  opening  is 
made  in  the  skin  in  the  occipital  region.  In  one  of  the  frogs, 
the  brain  and  spinal  cord  are  completely  destroyed  by  passing 
a  needle  upwards  and  downwards  from  the  occipital  region, 
and  then  both  are  hung  vertically  on  a  board,  side  by  side. 
looking  in  the  same  direction.  A  small  funnel,  the  stem  of 
which  is  drawn  out  into  a  narrow  beak,  is  now  passed  from  the 
incision  downwards  under  the  skin  of  each  animal,  till  its  end 
reaches  the  dorsal  Emphatic  sac.  This  done,  the  bulbus 
aortse  is  divided  in  both  animals,  and  the  results  are  observed. 
In  the  frog  deprived  of  its  central  nervous  system,  only  a  few 
drops  of  blood  escape — the  quantity,  that  is  to  say,  previously 
contained  in  the  heart  and  in  the  beginning  of  the  arterial 
system.  In  the  other,  the  bleeding  is  not  only  more  abundant, 
but  continues  for  several  minutes  after  the  section.  As  soon 
as  bleeding  has  ceased,  a  quantity  of  saline  solution  (say,  5  to 
10  centimetres)  is  injected  into  the  lymphatic  sac  of  each  animal 
until  it  is  distended,  and  the  exact  quantity  used  carefully 
noted.  In  the  frog  in  which  the  central  nervous  system  is 
intact,  the  discharge  of  blood  from  the  opening  in  the  bulb 
begins  again,  and  goes  on  increasing;  while  the  liquid,  which 
at  first  is  nearly  pure  blood,  becomes  more  and  more  diluted 
with  serum.  The  discharge  of  sanguineous  liquid  goes  on  for 
one  or  two  hours  ;  and  if,  during  the  progress  of  the  experi- 
ment, the  vasomotor  centre  is  stimulated  reflexl\-  by  exciting 
a  sensory  nerve  or  the  surface  of  the  skin,  it  is  seen  that  the 
rate  of  flow  is  at  once  augmented,  but  becomes  less  after  the 
cessation  of  the  excitation  than  it  was  before.     This  last  fact 

1  Colored  drawings  of  the  injections  so  obtained  "will  be  found  in  Lud- 
wig and  Schweigger-Seidel's  beautiful  monograph  on  the  lymphatics  of 
tendons  and  aponeuroses. 


BY    DR.    BURDON-SANDERSON.  297 

is  thought  by  Goltz,1  the  author  of  this  experiment,  to  indicate 
that  when  a  sensory  nerve  is  excited,  venous  absorption  is  in- 
creased. It  may  perhaps  be  attributable  rather  to  the  contrac- 
tion of  the  vessels  which  is  determined  by  the  excitation.  To 
render  the  observation  of  the  result  as  accurate  as  possible, 
the  quantity  discharged  should  be  measured.  The  quantity 
found  in  the  test-glass  in  which  the  mixture  of  blood  and  serum 
is  collected  should,  together  with  the  residue  remaining  in  the 
lymph  sac,  be  equal  to  the  quantity  originally  injected. — In 
the  other  frog  there  is  no  discharge.  The  heart  remains  flaccid 
although  contracting  regularly,  and  the  skin  dry  from  the  arrest 
of  the  secretion  of  the  cutaneous  glands.  In  this  experiment 
it  may  be  supposed,  either  that  the  liquid  contained  in  the 
lymph  sac  passes  into  the  circulation  directly,  or  that  it  first 
diffuses  out  into  the  surrounding  tissue,  and  is  then  absorbed 
by  the  veins.  The  first  supposition  is  negatived  b}r  the  obser- 
vation that  the  contractions  of  the  lymph  hearts  have  ceased 
in  both  frogs,  and  that  consequently  the  mechanism  by  which 
alone  the  liquid  could  be  directly  transferred  to  the  venous 
system  is  wanting.  We  are,  therefore,  compelled  to  admit  that 
it  enters  the  blood-stream  by  the  only  other  channel  open  to 
it;  and  the  conditions  of  the  experiment  prove  that  it  does  so 
under  the  direct  influence  of  the  nervous  system. 

The  precise  nature  of  the  agency  by  which  the  living  ele- 
ments which  surround  the  bloodvessels  determine  the  diffusion 
of  liquid  into  the  blood  in  opposition  to  pressure,  cannot  at 
present  be  stated.  In  the  instance  before  us,  two  sets  of  effects 
may  be  distinguished  as  referable  to  one  cause,  i.  e.,  destruc- 
tion of  the  central  nervous  system — those  due  to  paralytic 
relaxation  of  the  bloodvessels,  and  those  which  are  attributable 
to  absence  of  absorption.  In  how  far  those  of  the  second 
kind  are  the  immediate  result  of  the  others,  may  perhaps  be 
open  to  question.  They  do  not,  however,  afford  any  explana- 
tion of  them,  for  there  is  no  reason  why  a  relaxed  vessel 
should  not  absorb  quite  as  much  as  a  contracted  one  ;  the  fact 
of  relaxation  affords  no  explanation  whatever  of  the  absence 
of  absorption.  Both  are  manifestations  of  properties  enjoyed 
by  the  living  elements  only  so  long  as  they  are  in  communica- 
tion with  cerebro-spinal  nervous  centres. 

1  "  Ueber  den  Einfluss  dcr  Nervencentren  auf  die  Aufsangung," 
Pflugers  Arcbiv.  B.  v.  p.  53. 


29S  RESPIRATION. 


CHAPTER  XVII. 

RESPIRATION. 

Section  I. — Preliminary   Study  of  the  External  Movements 
of  Respiration. 

86.  Respiratory  Movements  of  the  Frog. — To  ob- 
serve the  respiratory  movements  in  the  frog,  the  animal  must 
be  fixed  on  its  back.  It  is  seen  that  that  part  of  the  floor  of 
the  pharyngeal  cavity  which  corresponds  to  the  submaxillary 
space,  e.  e..  to  the  space  which  lies  between  the  episternal  car- 
tilage, and  the  two  branches  of  the  lower  jaw  bone,  alternately 
rises  and  falls  at  intervals  of  about  one  or  two  seconds.  On 
more  attentive  examination,  it  is  found  that  these  movements 
are  clue  to  the  alternate  retraction  and  advance  of  the  body  of 
the  hyoid  bone,  the  general  form  of  which  can  be  readily  dis- 
tinguished under  the  skin.  To  study  their  nature,  the  skin 
must  be  divided  in  the  middle  line  from  the  mouth  to  the 
sternum,  and  detached  from  the  subjacent  muscles  as  far  out- 
wards on  either  side  as  the  jaw.  In  this  way  a  view  is  ob- 
tained of  all  the  muscles  attached  to  the  hyoid  bone,  without 
interfering  with  the  mechanism  of  respiration  (see  fig.  246). 
By  its  long  and  slender  anterior  horn,  the  hyoid  bone  is  con- 
nected with  the  skull  (t.  e.,  with  the  cartilaginous  part  of  the 
petrous  bone)  in  such  a  manner  that,  although  the  two  car- 
tilages are  not  united  by  a  joint,  the  hyoid  works  on  the 
petrous  bones  as  if  it  were  hinged  to  them.  This  being  borne 
in  mind,  it  is  easy  to  understand  the  action  of  the  muscles 
which  are  attached  to  it.  Those  which  come  from  the  sternum 
and  bones  connected  with  it,  in  drawing  the  hyoid  backwards, 
cause  it,  at  the  same  time,  to  descend  in  such  a  way  as  to  in- 
crease the  space  between  its  upper  surface  and  the  roof  of  the 
mouth  and  pharynx,  and  to  extend  that  part  of  the  submax- 
illary space  which  intervenes  between  the  arch  of  the  hyoid 
and  that  of  the  lower  jaw.  On  the  other  hand,  those  muscles 
which  stretch  from  the  chin  (the  genio-hyoid),  and  from  the 
petrous  bones  (the  petrohyoid  muscles)  to  the  bod}*  of  the 
bone,  combine  in  drawing  it  upwards  and  forwards,  to  such  a 
degree,  indeed,  that  when  the  latter  are  in  action,  the  sub- 
maxillaiy  space  becomes  concave.  All  this  can  be  readily 
seen  in  the  living  animal;  for  although  the  muscles  above- 
mentioned  are  covered   by   the    submaxillary    or   mylohyoid 


BY    DR.    BUR  DON-SANDERSON.  299 

muscles,  this  muscular  membrane  is  so  thin  that  they  can  be 
easily  perceived  through  it. 

To  investigate  the  part  taken  by  these  movements  in  the 
mechanism  of  respiration,  it  is  necessary  to  ascertain  in  what 
relation  they  stand  to  the  influx  and  efflux  of  air.  This  is 
accomplished  by  inserting  a  suitable  glass  canula  into  one  of 
the  nostrils  and  connecting  it  with  the  tympanum,  shown  in 
fig.  231.  In  this  way  the  curve  is  obtained,  which  is  copied  in 
fig.  246  bis.  By  watching,  at  the  same  time,  the  motions  of 
the  hyoid  bone  and  of  the  lever,  it  is  easy  to  satisfy  one's  self 
that  the  retraction  of  the  former  towards  the  sternum  corres- 
ponds with  the  depression  of  the  latter,  and  with  the  entrance 
of  air  into  the  pharyngeal  cavity.  It  is  further  seen  that  the 
motions  are  by  no  means  uniform,  and  that  in  connection  with 
this  want  of  uniformity  they  present  certain  peculiarities  which, 
from  their  intimate  connection  with  the  mechanism  by  which 
air  is  introduced  into  and  expelled  from  the  lungs,  require 
careful  attention.  The  tracing  enables  us  to  divide  the  respira- 
tory acts  into  two  kinds,  viz.,  smaller  alternative  movements 
(a  a  a),  which  occur  at  pretty  regular  short  intervals,  and  larger 
movements  (bbb),  which  differ  from  the  others  in  this  respect, 
that  the  less  energetic  expiratory  act  by  which  the  movement 
begins,  terminates  in  a  sudden  expulsion  of  air,  indicated  by  a 
more  rapid  rise  of  the  lever,  and  determined  by  a  more  vigor- 
ous contraction  of  those  muscles  which  connect  the  body  of  the 
hyoid  bone  with  the  skull.  This  sudden  elevation  of  the  floor 
of  the  pharynx  is  the  act  by  which  the  frog  injects  air  into  its 
lungs.  The  student  must  now  fix  his  attention  on  the  nostrils, 
when  he  will  see  that  whereas  during  the  small  movements 
(a  a)  those  organs  are  motionless,  the  sudden  expulsions  (b  b) 
are  accompanied  by  contraction  of  the  little  constrictor  mus- 
cles of  the  nares,  and,  consequently,  that  the  latter  differ  from 
the  former  not  merely  in  their  greater  vigor,  but  in  their  being 
executed  witli  the  nostrils  more  or  less  closed,  so  that  the  air, 
instead  of  passing  freely  out,  is  injected  through  the  glottis  into 
the  lungs.  To  prove  this,  watch  the  expiratory  muscles  of  the 
flanks  (the  external  oblique  particularly).  At  the  first  moment, 
it  will  perhaps  appear  as  if  the  sudden  contraction  of  these 
muscles  were  coincident  with  the  closure  of  the  nares,  but  it  is 
soon  seen  that  the  former  movement  follows  the  latter  at  an 
interval  of  time,  which,  although  very  short,  is  not  difficult  to 
appreciate  even  without  instruments.  This  may  be  demon- 
strated graphically  by  puncturing  the  anterior  wall  of  the  vis- 
ceral cavity,  and  introducing  through  the  puncture  a  canula 
in  such  a  way  that  it  communicates  with  the  cavity  of  one  lung. 
The  canula  being  connected  with  a  tympanum, a  tracing  is  ob- 
tained, which  shows  that  the  period  during  which  the  air  is 
contained  in  the  lungs  is  extremely  short,  that  the  entry  of  air 


300  RESPIRATION. 

into  the  lungs  coincides  with  the  closure  of  the  nares,  and  is 
determined  by  the  approximation  of  the  body  of  the  hyoid 
bone  to  the  roof  of  the  pharynx,  and  that  the  expulsion  of  air 
from  the  lungs  by  the  contraction  of  the  Hanks  occurs  while 
the  hyoid  is  still  drawn  upwards,  so  that  the  two  muscular 
movements  form  part  of  the  same  act. 

87.  External  Respiratory  Movements  of  Man  and 
Mammalia. — The  alternate  emptying  and  filling  of  the  air 
cells  of  the  lungs,  which  is  the  final  cause  of  respiration,  is 
effected  by  the  alternate  enlargement  and  contraction  of  the 
chest.  If  the  whole  of  the  thorax  were  occupied  by  the  air 
cells,  these  changes  of  capacit}'  could  be  measured  by  the  quan- 
tity of  air  entering  and  leaving  the  respiratory  cavity  in  each 
act  of  breathing.  As,  however,  in  addition  to  the  lungs,  the 
chest  contains  various  other  organs,  some  of  which  alter  their 
volume  very  considerably,  according  to  the  degree  of  expansion 
of  the  cavity  in  which  they  are  contained,  there  is  no  constant 
relation  between  the  enlargement  or  diminution  of  the  available 
intra-thoracic  air  space  and  the  external  enlargement  or  dimi- 
nution of  the  thorax. 

There  is  no  practicable  method  of  determining  the  changes 
of  volume  which  the  chest  undergoes  in  respiration  with  exacti- 
tude. As,  however,  the  imperfect  methods  we  possess  differ 
from  most  of  those  employed  in  physiology,  in  being  quite  as 
applicable  to  man  as  to  the  lower  animals,  and  are  sufficiently 
accurate  to  yield  valuable  results  in  the  study  of  disease,  they 
are  well  worthy  of  the  attention  of  the  phj'sician,  though  of 
comparatively  little  interest  to  the  physiologist. 

88.  The  external  movements  of  the  human  chest  maybe  in- 
vestigated by  recording  the  variations  either  of  its  diameters 
or  of  its  circumference,  at  different  parts,  or  of  both  simulta- 
neously. For  the  graphic  measurement  of  the  circumference, 
an  instrument  contrived  by  Marey,  and  much  improved  by 
Bert,  is  used.  It  consists  of  an  air-tight  cylinder  of  brass  and 
India-rubber,  of  the  shape  and  construction  of  a  common  drum, 
the  cylinder  being  of  brass  and  the  membranous  ends  of  India- 
rubber.  The  cylinder  communicates  by  a  flexible  tube  with  a 
tympanum,  the  lever  of  which  records  its  variations  of  capacity. 
To  the  centre  of  each  of  the  two  terminal  membranes  a  metal 
disk  is  attached,  which  is  furnished  with  a  hook,  and  is  thus 
connected  with  one  of  the  ends  of  an  inelastic  cincture,  which 
encircles  the  circumference  to  be  measured.  As  the  circum- 
ference augments,  the  membranes  are  extended,  and  the  ca- 
pacity of  the  drum  increased,  and  vice  versa.  It  is  obvious 
that  before  the  instrument  is  used  it  must  be  graduated.  The 
mode  of  accomplishing  this  will  be  given  further  on. 

89.  The  graphic  measurement  of  the  diameters  of  the  chest 
is  much  more  simple,  inasmuch  as  it  merely  involves  the  trans- 


BY   DR.    BURDON-SANDERSON.  301 

lation  to  the  paper  of  the  movement  produced  by  the  alternate 
recession  from  each  other,  and  approximation  to  each  other, 
of  two  points  in  the  chest  wall  at  the  opposite  extremities  of 
the  diameter  to  he  measured  ;  so  that  if  either  of  these  points 
be  taken  as  fixed,  the  recording  of  the  movement  of  the  other 
point  amounts  to  nothing  more  than  the  conversion  of  one 
rectilinear  movement  into  another.  This  is  readily  accom- 
plished by  the  contrivance  we  have  already  employed  for  re- 
cording the  external  cardiac  movements  (see  §  60),  that  is,  by 
the  employment  of  two  tympana,  the  one  for  receiving  the 
movement  to  be  investigated,  the  other  for  inscribing  it  on  the 
cylinder.  The  receiving  tympanum  must  be  so  placed  that 
the  distance  of  its  India-rubber  membrane  from  the  fixed 
extremity  of  the  diameter  to  be  investigated,  is  subject  to  no 
variation  during  the  period  of  measurement,  and  that  its  ivory 
button  is  applied  to  the  movable  end  in  such  a  way  that  the 
diameter,  if  produced  beyond  the  surface  of  the  chest,  would 
coincide  with  its  axis.  All  these  conditions  are  completely 
fulfilled  in  the  instrument  I  use.  It  consists  of  two  parallel 
bars  of  iron,  the  opposite  ends  of  which  are  screwed  firmly  at 
right  angles  into  a  cross  bar,  so  as  to  form  a  rigid  frame  re- 
sembling in  shape  the  Greek  letter  n.  The  diameter  to  be 
investigated  is  placed  between  the  extremities  of  these  bars. 
One  of  these  carries  an  ivory  knob,  similar  to  that  of  the 
cardiograph,  the  convexity  of  which  looks  towards  the  oppo- 
site arm.  Its  distance  may  be  varied  by  a  screw.  The  other 
arm  beai's  the  receiving  tympanum,  the  knob  of  which  faces 
the  knob  just  mentioned,  their  axis  being  in  the  same  line. 

The  mode  of  application  of  the  instrument,  which  may  be 
conveniently  called  a  recording  stethometer,  varies  according 
to  the  diameter  to  be  measured.  The  most  important  diame- 
ters are  those  which  connect  the  8th  rib  in  the  axillary  line 
with  the  same  rib  of  the  opposite  side,  the  manubrium  sterni 
with  the  3d  dorsal  spine,  the  lower  end  of  the  sternum  with  the 
8th  dorsal  spine,  and  the  ensiform  cartilage  with  the  10th  dor- 
sal spine.  The  mode  of  application  for  the  first  of  these  diame- 
ters is  shown  in  fig.  247.  The  subject  stands  or  sits,  as  is 
most  convenient,  and  the  stethometer  is  hung  over  his  neck 
by  a  broad  band,  the  length  of  which  can  be  regulated  by  a 
buckle.  The  movements  recorded  are  not  those  which  the 
middle  of  the  8th  rib  performs  in  relation  to  its  stdrnal  and 
vertebral  attachments,  but  those  which  the  one  end  of  the 
diameter  executes  in  relation  to  the  other,  which  is  for  the 
moment  regarded  as  a  fixed  point.  In  measuring  the  diame- 
ters which  lie  in  the  middle  plane,  it  is  most  convenient  to 
take  the  vertebral  spines  as  fixed  points,  although,  of  course, 
the  results  would  not  be  affected  by  doing  otherwise.  The 
records  obtained  by  the  stethometer  are  of  value  for  two  pur- 


302  RESPIRATION. 

poses,  viz.,  for  the  appreciation  of  the  relative  and  absolute 
duration  of  the  respiratory  acts,  and  for  the  measurement  of 
their  extent.  For  the  latter  purpose,  the  instrument  must  be 
graduated  every  time  that  it  is  Used.  To  facilitate  this  pro- 
cess, I  employ  a  set  of  five  standard  wooden  measures  of 
length,  differing  from  each  other  by  two  millimetres.  With 
these,  the  graduation  is  effected  in  less  than  five  minutes.  The 
recording  and  receiving  tympana  having  been  brought  into 
communication,  and  the  whole  system  tested  as  regards  the 
perfection  of  the  joints,  and  found  to  be  air-tight,  one  of  the 
wands  (the  one  of  which  the  length  is  equal  to  the  mean  of  the 
five)  is  placed  between  the  two  buttons  of  the  stcthometer, 
which  are  then  approximated  until  the  India-rubber  membrane 
of  the  tympanum  is  slightly  concave.  A  horizontal  tracing 
having  been  drawn  on  the  cylinder,  the  two  next  longest  and 
shortest  wands  are  substituted  for  the  first,  and  the  process  is 
repeated  in  respect  of  each,  and  then  the  next  two,  until  five 
parallel  horizontal  lines  have  been  drawn,  by  comparison  with 
which,  the  variations  of  the  diameters  investigated  may  be 
estimated  in  millimetres  from  the  vertical  measurements  of  the 
tracings.  By  this  method  we  learn,  for  example,  that  in  a 
healthy  muscular  j-oung  man,  aged  22,  the  diameters  above 
given  vary  respectively  in  each  respiration  as  follows  :  Upper 
sternal  diameter= 146,  varies  one  millimetre;  the  lower  ster- 
nal diameter  =  203,  varies  1.5 — 1.8  millimetre;  the  transverse 
costal  diameter  =  228,  varies  1.7 — 2.0  millimetres. 

As  regards  the  duration  and  succession  of  the  respiratory 
acts,  the  most  instructive  curves  are  the  costal  and  lower 
sternal  (see  fig.  248).  It  must  be  carefully  borne  in  mind 
that  they  apply  strictly  to  natural  respiration.  In  forced 
breathing,  the  thoracic  movements  acquire  a  different  char- 
acter. Dr.  Arthur  Ransome,  who  has  studied  the  subject 
with  great  accuracy,  allows  me  to  refer  to  his  measurements. 
He  has  found  that  the  variations  of  the  antero-posterior  diame- 
ters of  the  upper  part  of  the  chest  are  very  extensive,  and 
that  the  whole  thoracic  framework  participates  in  them — the 
ends  of  the  upper  ribs  moving  horizontally  forward,  i.  e.,  in  a 
plane  parallel  to  the  middle  plane  of  the  body,  from  12  to  30 
millimetres;  the  advance  of  the  third  rib  is  greater,  by 
several  millimetres,  than  that  of  the  fifth.  Dr.  Ransome  con- 
siders that  this  advance  cannot  be  otherwise  accounted  for 
than  b}'  an  actual  bending  of  the  ribs. 

We  shall  see  afterwards  that  the  difference  between  natural 
and  forced  breathing  consists  partly  in  increased  constriction 
of  the  chest  during  expiration,  partly  in  increased  expansion 
during  inspiration.  In  the  meantime,  it  is  sufficient  to  note 
that  when  the  thoracic  movements  become  excessive,  the 
change  affects  the  antero-posterior  diameters  of  the  upper  part 


BY    DR.    BURDON-SANDERSON.  303 

of  the  chest  more  than  of  the  lower  part,  so  that  the  normal 
.relation  between  the  two  is  reversed. 

90.  Measurement  of  the  Intra-Thoracic  Pressure. 
—In  consequence  of  the  elasticity  of  the  lungs,  and  of  the 
fact  that  they  are  contained  in  a  cavity  of  which  the  capacity 
is  much  greater  than  the  volume  which  these  organs  assume 
in  their  unextended  condition,  and  that  their  external  surface 
is  inseparably  applied  to  the  inner  surface  of  the  cavity,  the 
pressure  to  which  the  heart,  arteries,  veins,  and  other  intra- 
thoracic organs  are  subjected,  is  considerably  less  than  that  of 
the  atmosphere.  What  is  required  to  measure  the  difference 
is  to  connect  one  pleural  cavity  with  a  manometer.  This  is 
easily  effected  in  the  following  manner :  A  glass  tube  of  about 
three  millimetres  in  diameter  is  sealed  at  one  end,  and  drawn 
out  to  a  blunt  point.  A  hole  is  then  cut  with  a  sharp  three- 
cornered  file  on  one  side  of  the  tube,  close  to  the  sealed  end, 
and  the  open  end  temporarily  closed  with  a  plug  of  wax.  A 
rabbit  having  been  secured  on  the  rabbit  support,  the  skin  is 
perforated  with  a  scalpel  close  to  the  left  edge  of  the  middle 
of  the  sternum.  This  having  been  done,  the  point  of  the  tube 
is  easily  passed  into  the  right  pleura  by  pushing  it  in  a  hori- 
zontal direction  behind  the  sternum,  with  its  point  against  the 
posterior  (i.  e.,  as  the  animal  is  placed,  the  under)  surface  of 
the  thoracic  wall.  The  wax  plug  is  then  removed,  and  the 
open  end  is  connected  with  a  water  manometer;  but  while  this 
is  being  done,  great  care  must  be  taken  to  keep  the  side  of  the 
tube  on  which  the  orifice  is,  firmly  but  gently  applied  against 
the  chest  wall.  The  quantity  of  water  in  the  manometer  is 
then  increased  or  diminished  until  the  two  columns  stand  at 
the  same  level.  If  now  the  tube  is  twisted  round  so  that  its 
orifice  looks  towards  the  cavity  of  the  chest,  the  distal  column 
sinks,  the  difference  between  the  heights  of  the  two  columns 
in  millimetres  being  about  thirteen  times  as  great  as  the  dif- 
ference in  millimetres  of  mercury  between  the  atmospheric 
pressure  and  that  to  which  the  thoracic  organs  are  subjected 
in  the  animal  under  observation.  The  intra-thoracic  pressure 
may  also  be  measured  indirectly  immediately  after  death,  by 
connecting  the  trachea  air-tight  with  a  manometer,  and  then, 
after  seeing  that  the  two  columns  stand  at  the  same  level, 
opening  both  pleural  cavities.  This  time  the  distal  column 
rises  above  the  proximal.  The  difference  between  them,  if  the 
same  kind  of  animal  is  used,  will  be  the  same,  though  in  the 
opposite  direction.  If  it  is  desired  to  obtain  a  record  of  the 
variations  of  intra-thoracic  pressure  during  the  respiratory 
acts,  it  is  easily  done  by  bringing  the  tube  into  communica- 
tion with  a  Marey's  tympanum,  by  means  of  a  somewhat  thick- 
walled  India-rubber  connector.  In  this  way  the  tracing,  fig. 
249,  is  obtained. 


>04  RESPIRATION. 


Section  II. — Study  of  tiik  Mode  of  Action  of  the  Muscles  of 
Respiration. 

In  man,  the  entry  of  air  into  the  chest  in  tranquil  breathing 
is  accomplished  exclusively  by  the  diaphragm.  In  the  dog,  it 
is  effected  partly  by  the  descent  of  the  diaphragm,  partly  by 
the  widening  of  the  chest.  In  the  rabbit,  the  respiratory 
movements  resemble  in  their  general  character  those  of  man, 
on  which  account  this  animal  is  preferable  to  any  other  for 
the  purposes  of  study.  From  the  fact  just  stated,  it  is  ob- 
vious that  in  our  examination  of  the  action  of  the  muscles  of 
respiration,  we  must  not  confine  ourselves  to  the  normal 
breathing,  for  if  we  were  to  do  so,  our  studies  would  relate 
almost  exclusively  to  one  muscle.  To  observe  the  action  of 
the  others,  we  must  direct  our  attention  to  the  excessive  tho- 
racic movements  of  animals  affected  more  or  less  with  dyspnoea, 
the  phenomena  of  which  condition,  so  far  as  they  relate  to 
the  action  of  muscles,  must  therefore  be  entered  upon  here, 
although  its  nature  and  cause  will  form  the  subject  of  a  special 
section. 

The  muscular  movements  by  which  the  chest  is  expanded, 
must  be  studied  in  their  relation  to  a  certain  definable  position 
of  the  thorax,  which  is  called  the  position  of  equilibrium.  It 
is  the  position  assumed  by  it  at  the  end  of  normal  expiration. 
For  as  no  muscle  takes  part  in  the  normal  expiratory  act,  the 
whole  thoracic  muscular  apparatus  is  at  that  moment  in  a 
state  of  rest,  the  bones  and  cartilages  assuming  that  position 
which  results  from  the  balance  of  the  opposed  elastic  forces, 
which  act  upon  them  from  within  and  from  without.  Of  these 
elastic  forces,  the  most  important  is  that  of  the  lungs  ;  which 
organs,  being  contained  in  a  cavity  much  larger  than  they  are 
themselves,  to  the  inner  surface  of  which  their  external  sur- 
face is  inseparably  applied,  constantly  draw  together  its  walls 
with  a  force  to  be  investigated  in  a  future  paragraph.  Next 
in  importance  is  the  elasticity  of  the  ribs  and  cartilages,  by 
virtue  of  which  the  thoracic  wall  ever  tends  to  be  larger  than 
it  is,  in  opposition  to  the  contractile  influence  of  the  lungs. 
Co-operating  with  these,  we  have,  thirdly,  the  "tonus"  of  the 
thoracic  muscles,  different  indeed  in  its  nature,  but  indis- 
tinguishable as  regards  its  action.  All  the  muscles  by  which 
the  chest  is  enlarged  beyond  the  position  of  equilibrium  are 
called  inspiratory  ;  all  those  by  which  it  is  contracted  to  a 
capacity  less  than  that  which  it  possesses  when  in  equilibrium 
are  called  expiratory. 

91.  Inspiratory  Muscles. —  The  Diaphragm. — To  demon- 
strate the  action  of  the  diaphragm,  several  methods  may  be 
used.  The  most  striking  is  to  expose  it  in  an  animal  made 
completely  insensible  by  the  injection  of  from  twenty  to  forty 


BY    DR.    BURDON-SANDERSON.  305 

minims  of  a  ten  per  cent,  solution  of  chloral  into  the  crural 
vein.  For  this  purpose  the  abdominal  cavity  must  be  opened 
in  the  linea  alba,  immediately  below  the  ensiform  cartilage,  and 
then  two  incisions  must  be  made,  extending  from  the  opening 
in  opposite  directions  parallel  to  the  edges  of  the  costal  car- 
tilages, according  to  the  instructions  given  in  §  56.  Another 
method  consists  in  merely  making  an  opening  in  the  linea  alba, 
close  to  the  ensiform  cartilage,  sufficient  to  receive  the  finger, 
the  tip  of  which  must  be  pressed  against  the  centrum  tendi- 
neum,  when  the  movements  can  be  appreciated  with  great  ex- 
actitude. The  plan  most  used  consists  in  introducing  a  long 
and  slender  needle  into  the  chest  through  the  ensiform  carti- 
lage, close  to  the  lower  end  of  the  sternum,  the  direction  of 
which  is  such,  that  it  grazes  the  upper  surface  of  the  diaphragm, 
if  possible  piercing  it  at  one  or  two  points,  so  as  to  be  in  some 
part  of  its  course  on  the  abdominal  side  of  the  membrane. 
For  this  experiment,  the  rabbit  must  be  carefully  chloralized, 
and  secured  on  Czermak's  supporter  in  such  a  way  that  the 
spinal  column  is  immovable.  A  long  silk  thread  is  then  passed 
through  the  eye  of  the  needle  and  connected  with  the  little 
bow-wood  pulley  shown  in  fig.  250,  the  movements  of  which 
are  inscribed  by  means  of  the  horizontal  lever  on  the  blackened 
cylinder.  The  tracing  so  obtained  enables  us  not  only  to  de- 
termine to  what  relative  distance  the  dome  of  the  diaphragm 
descends  in  each  inspiratory  act,  but  also  the  mean  relaxation 
of  the  muscle,  i.  e.,  the  mean  height  to  which  it  ascends  during 
each  expiration.  This,  as  we  shall  see  further  on,  is  much 
affected  by  conditions  which  act  on  the  muscle  by  its  motor 
nerve. 

92.  Intercostal  Muscles. — To  demonstrate  the  action  of  the 
intercostal  muscles,  a  rabbit  is  used  which  has  been  deprived 
both  of  voluntary  motion  and  of  sensibility  by  the  ablation  of 
the  cerebral  hemispheres  as  well  as  of  the  corpora  striata  and 
thalami  optici.  This  operation  is  performed  as  follows  :  The 
animal  having  been  rendered  insensible  by  chloroform,  both 
carotids  are  tied.  It  is  then  secured  on  the  supporter  in  the 
prone  position.  The  calvarium  is  now  exposed  by  an  incision 
extending  from  the  occiput  to  the  frontal  region  in  the  middle 
line,  and  the  integument  drawn  aside  in  either  direction.  The 
parietal  bones  having  been  first  perforated  with  the  trephine, 
to  allow  of  the  introduction  of  the  cutting  pliers,  the  roof  of 
the  cranium  is  rapidly  removed  so  as  to  expose  the  hemi- 
spheres completely.  These  organs  are  then  scooped  out  with 
the  ivory  handle  of  a  scalpel,  an  assistant  being  at  hand  with 
the  actual  cautery  to  arrest  the  bleeding.  The  animal  at  once 
passes  ii'to  a  state  resembling  deep  sleep,  breathing  regularly, 
bat  much  more  slowly  than  before  the  operation.  The  action 
of  the  respiratory  muscles  of  the  chest  can  now  be  investigated 
20 


306*  RESPIRATION. 

without  any  misgiving  as  to  the  infliction  of  suffering,  by  re- 
moving the  integument  and  superficial  layer  of  muscles  80  as 
to  expose  the  ribs  and  intercostal  Bpaces. 

The  first  lesson  to  be  learnt  relates  to  normal  breathing.  It 
it  seen  that  so  long  as  air  enters  the  chest  freely,  ami  the  res- 
piratory apparatus  is  not  interfered  with,  there  is  no  appreci- 
able expansive  movement  of  the  ribs,  ami  the  intercostal  mus- 
cles, in  so  far  as  they  are  visible,  do  not  contract.  Dyspnoea 
may  now  be  produced,  either  by  letting  air  into  one  or  both  of 
the  pleural  cavities,  by  diminishing  the  opening  by  which  the 
chest  communicates  with  the  atmosphere,  or  by  combining  the 
two  methods.  It  is  most  convenient  to  begin  with  puncturing 
one  pleura. 

The  effect  of  this  operation  is  to  increase  the  respiratory 
movements,  and  to  alter  their  character  by  bringing  the  tho- 
racic muscles  into  action.  The  upper  ribs,  particularly  the 
second,  third,  and  fourth,  which  were  before  motionless,  move 
upwards  and  outwards  in  each  inspiration,  while  the  external 
intercostal  muscles,  and  the  intercartilaginous  parts  of  the  in- 
ternal intercostal,  are  seen  to  grow  hard  in  contraction  at  the 
same  moment. 

To  produce  a  higher  degree  of  dyspnoea,  the  other  pleura 
may  be  opened;  the  principal  effect  observed  is  that  the  upward 
and  outward  movement  of  the  upper  ribs  is  increased,  and  that 
the  scaleni,  which  were  before  inactive,  now  begin  to  contract 
in  concert  with  the  external  intercostals.  These  muscles, 
although  from  their  anatomical  arrangement  the}'  must  act  as 
elevators  of  the  ribs,  cannot  be  shown  to  be  so  experimentally ; 
for  there  is  no  appreciable  diminution  of  the  costal  movement 
when  they  are  divided. 

The  function  of  the  external  intercostals  and  intercartilagi- 
nous muscles,  having  been  proved  by  direct  observation  in  the 
manner  above  described,  at  a  very  earl}'  period  in  the  history 
of  physiology,  has  never  been  seriously  disputed.  This  is  not 
however  the  case  as  regards  the  interosseous  part  of  the  internal 
intercostals — that  part  of  those  muscles  which  is  covered  by  the 
external  intercostals.  In  the  rabbit,  the  interosseous  intercos- 
tals differ  from  the  intercartilaginous,  both  in  being  less  oblique 
and  in  being  somewhat  thinner.  The  experimental  evidence 
as  to  their  function  is  negative — that  is  to  say,  it  can  be  shown 
that  the}'  do  not  contract  with  the  external  muscles,  but  it 
cannot  be  shown  that  the}'  act  antagonistically  to  them.  It 
admits  of  demonstration  as  regards  any  of  the  lower  ribs,  from 
the  fourth  to  the  eighth  or  ninth,  that  if  all  the  muscles  at- 
tached to  it  from  above  are  removed,  excepting  the  external 
intercostals  and  the  levatores  costarum  breves  (muscles  which 
connect  each  transverse  process  with  the  rib  next  below  it,  and 
can  be  seen  to  contract  with  the  external  intercostals),  the  rib 


BY  DK.  BURDON-S ANDERSON.  307 

still  rises  outwards  in  inspiration;  but  if  these  muscles  are 
completely  severed,  no  more  costal  movement  is  perceptible ; 
nor  is  there  any  hardening  of  the  exposed  intercostal  muscles 
at  the  moment  of  inspiration.  In  a  word,  it  must  still  be  ad- 
mitted that  the  action  of  these  muscles  is  as  }ret  undetermined. 
Most  probably  they  may  be  regarded  as  constrictors  of  the 
chest — as  the  agents  of  forced  expiration. 

93.  Movements  of  the  Nares  and  Larynx. — In  the 
rabbit,  the  nostrils  dilate  with  each  ordinary  inspiration,  and 
contrast  in  expiration;  but  from  their  frequency  these  move- 
ments are  very  difficult  to  observe.  To  study  them  satisfac- 
torily, the  student  must  avail  himself  of  the  excessive  and  in- 
frequent respirations  of  animals  in  which  both  vagi  have  been 
divided.  It  is  then  seen  that  the  dilatation  of  the  nares  is 
the  first  act  of  inspiration.  It  precedes  by  a  distinct  interval 
the  expansion  of  the  chest,  and  appears  even  to  precede  the 
contraction  of  the  diaphragm.  Whether  it  actually  does  so 
is  very  difficult  to  determine.  The  muscles  b}'  which  this 
movement  is  effected  are,  the  subcutaneous  faciei  which  springs 
from  the  lateral  surface  of  the  intermaxillary  bone,  and  from 
the  anterior  supraorbital  process  of  the  frontal  bone,  to  be  in- 
serted into  the  skin  of  the  nose  and  forehead,  and  the  levator 
nasi,  which  springs  from  the  lower  edge  of  the  orbit,  and  is 
also  inserted  by  a  long  tendon  into  the  skin,  covering  the 
edge  of  the  nose.  Of  the  two,  the  former  is  the  more  super- 
ficial. 

The  respiratory  movements  of  the  larynx  in  the  rabbit  are 
scarceby  perceptible  in  perfectly  natural  breathing;  but  the 
slightest  interference  with  the  access  of  air  to  the  chest  is  suf- 
ficient to  produce  them.  The  larynx  is  drawn  downwards  in 
inspiration  hy  the  muscles  connecting  it  with  the  sternum, 
and  returns  to  the  position  of  muscular  equilibrium  in  expira- 
tion. One  of  these  muscles,  the  sterno-thyroid,  has  also  the 
effect  of  tilting  forwards  the  thyroid  cartilage,  so  as  to  bring 
its  lower  edge  nearer  the  cricoid. 

94.  To  study  the  intrinsic  respirator}'  movements  of  the 
larynx,  the  rima  glottidis  must  be  exposed  to  observation,  by 
making  a  suitable  opening  either  above  or  below.  The  best 
view  of  the  movements  is  obtained  by  dividing  the  hyothyroid 
membrane.  The  skin  having  been  carefully  divided  in  the 
middle  line,  lege  ariis,  the  membrane  must  be  exposed  with 
the  aid  of  two  pairs  of  forceps.  The  veins  (which  are  the 
principal  source  of  difficulty)  can  then  be  readily  seen,  and 
must  be  carefully  secured  above  and  below  by  ligatures,  be- 
tween which  the  membrane  may  be  cut  across  without  risk  of 
hemorrhage.  The  head  must  of  course  be  so  supported  that 
a  strong  light  is  thrown  on  the  vocal  cords.  If  now  the  epi- 
glottis is  drawn  forwards,  the  motions  of  the  vocal  cords  and 


308  RESPIRATION. 

of  the  arytenoid  cartilages  are  well  seen — the  chink  becoming 
wider  in  inspiration,  narrower  in  expiration.  To  observe  the 
motions  of  the  arytenoid  cartilages,  the  best  way  is  to  excite 
the  recurrent  nerves,  when  it  is  seen  that  during  excitation 
the  vocal  cord  of  the  same  side  approaches  the  middle  line. 
If  both  recurrents  are  excited,  the  rima  is  completely  closed, 
the  arytenoid  cartilages  applying  themselves  to  each  other 
just  as  they  do  in  the  production  of  a  musical  note.  Con- 
sidering that  the  recurrent  nerve  is  distributed  to  all  the 
muscles,  and  not  merely  to  those  which  act  as  constrictors 
{aryteenoidei  and  crico-arytsenoidei  laterales),  and  that  the 
movements  produced  are  of  the  same  nature  as  those  which 
occur  in  ordinary  expiration,  though  much  more  vigorous,  we 
arrive  at  the  inference  that  in  both  cases  the  widening  of  the 
glottis  is  a  condition  of  general  muscular  relaxation,  or,  in 
other  words,  that  all  the  intrinsic  muscles  of  the  larynx  are 
expiratory — their  combined  effect  manifesting  itself  in  ap- 
proximation of  the  vocal  cords,  not  because  the  posterior 
crico-arytenoid  muscles  and  the  other  dilating  muscles  do  not 
act  with  the  rest,  but  because  they  are  overpowered  by  them. 

Section  III. — Measurement  of  the  Quantity  of  Air  respired  in 
a  given  Time,  and  of  the  Volume  of  Air  inhaled  in  each  Re- 
spiratory Act. 

95.  The  apparatus  for  this  purpose  consists  of  three  parts, 
viz.,  (a)  a  receiver  or  chamber  in  which  the  air  to  be  breathed 
during  the  period  of  observation  is  contained;  (b)  a  face-piece 
and  tube  for  connecting  the  receiver  with  the  respiratory 
cavit}^  of  the  subject  of  observation;  (c)  arrangements  for 
supplying  fresh  air  to  the  receiver,  to  take  the  place  of  the 
air  breathed. 

To  obtain  results  which  are  reliable,  the  first  and  most  im- 
portant condition  is  that  the  air  should  be  respired  without 
the  slightest  effort.  To  insure  this,  the  receiver  must  be  of 
such  construction  that  the  pressure  to  which  the  air  contained 
in  it  is  subjected  should  be  the  same  as  that  of  the  atmos- 
phere. Consequently,  it  must  have  the  form  either  of  a  gaso- 
meter, the  cylinder  of  which  is  accurately  counterpoised,  or 
that  of  a  membranous  bag,  the  material  of  which  is  so  thin 
that  it  offers  no  resistance  either  in  contracting  or  expanding. 
The  best  material  for  the  latter  purpose  is  vulcanized  India- 
rubber;  it  is,  however,  difficult  to  obtain  bags  of  this  descrip- 
tion which  are  perfect.  Whatever  be  its  form,  the  receiver 
must  have  two  openings,  one  communicating  with  the  face- 
piece,  the  other  for  the  reception  of  air.  It  must  be  also  so 
constructed  that  the  moment  at  which  it  is  full  may  be  easily 
and  accurately  observed. 


BY   DR.    BURDON-SANDERSON.  309 

The  receiver  is  brought  into  communication  with  the  expira- 
tory cavity  of  the  subject  of  experiment  by  means  of  a  face- 
piece  or  mask  of  very  perfect  construction,  furnished  with  two 
valves,  by  one  of  which  the  air  is  expelled,  while  the  other, 
opening  inwards,  guards  the  orifice  of  a  tube  about  an  inch  in 
width,  which  leads  from  the  receiver. 

By  its  second  opening,  the  receiver  communicates  with  a 
gasometer  filled  with  air,  under  a  pressure  somewhat  greater 
than  that  of  the  atmosphere.  Between  the  gasometer  and  the 
receiver,  the  tube  of  communication  passes  first  through  a 
stop-cock  of  brass,  the  aperture  of  which  can  be  regulated 
very  accurately  by  means  of  a  long  handle,  and  then  through 
an  accurately  graduated  gas  meter,  specially  constructed  for 
the  purpose.  Each  observation  lasts  ten  minutes.  The  gas- 
ometer is  kept  full  of  air  by  means  of  a  pair  of  bellows,  which 
must  be  worked  by  an  assistant  (in  default  of  other  motor) 
during  the  whole  period;  while  the  quantity  of  air  which  is 
driven  through  the  meter  to  the  recipient  is  so  regulated  with 
the  aid  of  the  stop-cock,  that  the  receiver  is  kept  exactly  at 
the  same  degree  of  fulness. 

The  chief  mechanical  source  of  inexactitude  in  this  appara- 
tus is  to  be  found  in  the  imperfect  closure  of  the  valves,  and 
imperfect  fitting  of  the  face-piece.  These  defects  may  be 
obviated  by  substituting  for  the  face-piece  a  couple  of  tubes  of 
ivory,  which  accurately  fit  the  anterior  opening  of  the  nostrils. 
The  wide  tube  with  which  these  ivory  nose-pieces  are  connected, 
at  once  divides  into  two  branches.  Of  these,  one  is  guarded 
by  a  mercurial  valve  leading  outwards,  the  other  by  a  similar 
valve  leading  inwards  for  inspiration,  the  arrangement  of  these 
valves  being  the  same  as  that  shown  in  fig.  251  to  be  imme- 
diately described. 

96.  In  making  observations  of  the  same  nature  on  the 
lower  animals,  it  is  convenient  to  use  an  apparatus  which  not 
only  admits  of  accurate  measurement  of  the  quantity  of  air 
breathed,  but  renders  it  possible  to  modify  its  composition  by 
the  introduction  of  definite  proportions  of  other  gases  or 
vapors.  And  inasmuch  as  in  such  investigations  it  is,  as  a 
rule,  of  more  importance  that  the  conditions  should  be 
accurately  known  than  that  they  should  be  identical  with 
those  normally  existing,  the  principle  of  completely  avoiding 
resistance,  which  was  regarded  as  fundamental  in  the  con- 
struction of  the  apparatus  described  in  the  preceding  para- 
graph, must  be  abandoned  ;  for  it  is  a  mechanical  impossibility 
to  construct  valves  which,  while  they  close  with  perfect 
accuracy,  work  without  resistance.  The  apparatus  to  be  now 
described  is  so  constructed  that  any  gaseous  mixture  may  be 
kept  in  it  for  a  length  of  time  without  change  of  composition 
by  diffusion,  and  the  valves  act  so  perfectly  that  the  experi- 


310  RESPIRATION. 

mentcr  is  absolutely  certain  that  the  whole  of  the  air  which 
leaves  the  receiver,  and  no  more,  is  actually  used  in  respiration. 

The  receiver  may  he  constructed  us  follows:  Two  glass 
cylinders  are  selected,  about  eight  inches  in  length,  open  at 
both  ends,  one  of  which  is  about  half  an  inch  wider  than  the 
other;  the  outer  is  about  three  inches  in  width,  the  inner  (e 
fig.  251)  two  and  a  half  inches.  Both  of  them  are  cemented 
in  the  most  perfect  manner  possible,  with  their  axes  in  the 
same  vertical  line  into  a  circular  horizontal  plate,  so  that  they 
are  separated  from  each  other  by  a  narrow  space  of  the  same 
width  everywhere.  This  space  is  to  be  filled  with  mercnry. 
Through  the  central  part  of  the  plate  rise  three  vertical  tubes 
of  glass,  of  about  a  quarter  of  an  inch  internal  diameter. 
Underneath  the  plate,  which  is  supported  on  a  tripod,  each  of 
these  tubes  passes  downwards  for  a  short  distance,  and  is 
then  bent  horizontally  at  right  angles.  A  third  cylinder  (o), 
closed  at  one  end  and  made  of  iron  carefully  protected,  con- 
stitutes the  bell  of  the  gasometer.  Its  diameter  is  the  mean 
of  the  diameters  of  the  two  cylinders  of  glass,  so  that  it 
descends  without  touching  them  into  the  space  containing 
mercury,  by  which  they  are  separated  from  each  other.  It  is 
suspended  by  a  silk  cord,  pulley,  and  counterpoise.  The 
counterpoise  consists  of  a  cup  containing  shot,  and  there  is  a 
second  and  similar  cup  on  the  top  of  the  cylinder.  Of  the 
three  tubes  which  enter  the  receiver  from  below,  one  (a)  com- 
municates with  the  atmosphere  (when  in  use),  a  second  (b) 
with  the  respiratory  cavity  of  the  animal,  the  third  (c)  is 
usually  closed.  The  India-rubber  tubes  by  which  these  com- 
munications are  made,  are  guarded  by  the  simple  contrivances, 
known  as  Midler's  mercurial  valves.  Each  such  valve  consists 
of  a  rather  wide  bottle  containing  a  shallow  column  of  mer- 
cury, and  closed  air-tight  with  an  India-rubber  stopper. 
Through  the  stopper  pass  two  tubes,  one  of  which  is  of  such 
length  that  its  end  dips  just  below  the  surface  of  the  mercury; 
the  other  is  much  shorter.  The  valve  (a)  is  so  placed  that  the 
short  tube  is  in  direct  communication  with  the  receiver,  the 
long  one  with  the  atmosphere  ;  in  (c)  this  arrangement  is  re- 
versed. To  complete  the  apparatus,  all  that  is  required  is  a 
T  tube  and  a  third  valve.  The  stem  of  the  T  tube  communi- 
cates with  the  respiratory  cavit}-  b}'  means  of  a  canula  secured 
air-tight  in  the  trachea;  the  one  arm  with  the  receiver,  and  the 
other  with  the  valve  (b),  through  which  the  expired  air  is  dis- 
charged into  the  atmosphere.  The  quantity  of  air  used  by 
the  animal  during  any  given  period  of  observation  must  be 
measured  in  the  same  way  as  before. 

The  objection  to  which  this  apparatus  or  any  other  of 
similar  construction  is  liable,  lies,  as  has  been  already  hinted, 
in   the  resistance  offered   by  the   mercurial   valves,  which  is 


BY    DR.    BURDON-SANDERSON.  311 

sufficient  to  retard  the  respiratory  movements  to  a  sensible 
degree.  As,  however,  the  most  important  applications  of  the 
method  are  those  which  relate  to  the  influence  of  variable  con- 
ditions on  the  quantity  of  air  breathed,  this  fact  is  of  little 
consequence;  for  the  error  arising  from  it  may  be  entirely 
eliminated  b}-  substituting,  as  a  standard  of  comparison,  the 
respiration  already  modified  by  the  resistance,  for  normal 
respiration.  For  the  purpose  of  obtaining  such  a  standard, 
the  animal  must  be  allowed  to  breathe  common  air  through 
the  apparatus  for  some  time  before  making  any  other  observa- 
tion. 

Section  IV. — Determination  of  the  Quantity  op  Carbonic 
Acid  Gas  discharged  by  an  Animal  from  the  Lungs  and  Skin 
in  a  given  Time. 

97.  There  are  two  leading  methods  by  which  this  can  be 
accomplished.  One  of  them  is  that  of  Regnault  and  Reiset, 
which,  with  important  modifications,  has  been  used  by  Ludwig 
and  his  pupils.  The  animal  under  observation  is  contained  in 
an  air-tight  chamber,  which  communicates  with  a  second 
chamber  containing  oxj-gen.  The  chamber  communicates 
with  an  absorbing  apparatus,  through  which  the  air  passes  in 
a  continuous  current,  so  that  the  expired  carbonic  acid  gas  is 
removed  from  it  as  rapidly  as  it  is  formed,  its  place  being 
taken  up  by  exactly  the  same  volume  of  oxygen,  so  that  the 
constitution  of  the  air  remains  unchanged.  The  quantity  of 
carbonic  acid  gas  absorbed  is  calculated  from  the  increase  of 
weight  of  the  absorbing  apparatus  during  the  period  of  obser- 
vation. As  improved  by  Ludwig,  the  method  is  the  best 
suited  for  exact  experiments.  The  apparatus  is  described  in 
Ludwig's  Arbeiten  for  1869. 

The  second  method,  which  is  much  simpler,  and  sufficiently 
exact  when  for  comparative  investigations  as  to  the  influence 
of  various  physiological  and  pathological  conditions  on  the 
discharge  of  carbonic  acid  gas,  is  that  of  Pettenkofer.  It  is 
applicable  either  to  large  animals  or  small.  A  short  account 
of  Pettenkofer's  complete  apparatus  will  now  be  given,  as  an 
aid  to  the  understanding  of  the  application  of  the  same  method 
to  the  small  animals  in  common  use  for  physiological  and 
pathological  investigations.  Pettenkofer's  apparatus  consists 
of  three  parts,  viz.,  a  chamber  in  which  a  man  can  sit  or  stand 
comfortably;  a  large  wet  gas  meter,  which  communicates  with 
the  chamber  by  a  tube  ;  a  double-action  air-pump,  by  which 
air  is  continuously  drawn  through  the  meter  from  the  cham- 
ber ;  and,  lastly,  clockwork,  by  which  the  pump  is  worked. 
The  chamber,  which  is  of  metal  and  glass,  communicates  with 
the  external  air  during  the  period  of  observation  by  the  inter- 


312  RESPIRATION. 

stices  round  the  door,  which  serve  for  the  entrance  of  air,  and 
by  the  tube,  which  leads  to  the  meter.  The  quantity  of  air 
which  is  drawn  through  it  by  this  tube  amounts  to  about 
20,000  litres  (706.4  cubic  feet)  per  hour,  a  quantity  not  merely 
abundantly  sufficient  for  ventilation,  but  to  prevent  loss  or 
error  by  diffusion  into  the  air  through  the  chinks  round  the 
door.  It  is  quite  unnecessary  to  describe  the  aspirating  appa- 
ratus excepting  in  so  far  as  to  state  that  the  clockwork  is 
moved  by  a  weight,  which,  by  a  well-known  mechanical  con- 
trivance, is  constant^  wound  up  by  a  steam-engine. 

To  obtain  a  result,  we  must  be  able  to  determine  with  accu- 
racy, first,  the  duration  of  the  period  of  observation,  and, 
secondly,  the  quantitj'  of  carbonic  acid  gas  contained  in  the 
air  which  passes  out  of  the  chamber  during  that  period.  The 
latter  object  ma}'  be  attained  either  by  estimating  the  total 
weight  of  carbonic  acid  discharged,  or  by  measuring  the 
volume  of  air  aspired,  and,  simultaneously,  the  proportion  by 
volume  of  the  same  gas  contained  in  it.  In  the  apparatus 
above  described,  the  quantity  of  air  discharged  is  so  large 
that  it  would  not  be  possible  to  analyze  the  whole  of  it,  so 
that  the  second  of  the  two  alternatives  must  be  adopted. 
This  is  effected  not  by  taking  one  or  more  specimens  of  the 
discharged  air  from  time  to  time  and  analyzing  them  (for  this 
plan,  unless  a  very  great  number  of  analyses  were  made,  would, 
in  consequence  of  the  constant  irregularities  which  occur  in 
the  rate  of  discharge,  give  wrong  results),  but  by  causing  a 
definite  proportion  of  the  used  air  to  pass  through  an  absorb- 
ing apparatus,  and  measuring  the  total  quantity  of  carbonic 
acid  gas  contained  in  it  by  a  volumetrical  method  to  be  imme- 
diately described.  This  division  of  the  aspired  air  into  two 
parts,  one  to  be  measured  and  analyzed,  the  other  merely  to 
be  measured,  is  a  matter  of  great  difficulty  ;  for  it  obvioush/ 
involves  the  carrying  on  during  the  period  of  observation  of 
two  continuous  measurements —  i.  e.,  the  employment  of  two 
meters  instead  of  one,  each  of  which  must  give  results  which 
are  not  only  accurate  in  themselves,  but  must  correspond 
exactly  with  those  of  the  other.  As,  in  applying  the  method 
to  animals  so  small  that  the  whole  quantity  of  air  can  be 
analyzed,  this  difficulty  is  not  met  with,  it  is  not  necessary  to 
say  anything  as  to  the  means  of  obviating  it,  or  the  errors 
which,  in  spite  of  all  precautions,  it  occasions. 

98.  Application  of  Pettenkofer's  Method  to  the 
Determination  of  the  Discharge  of  Carbonic  Acid 
Gas  in  Small  Animals. — The  apparatus  consists  of  a  metal 
chamber  of  iron,  which  communicates  in  one  direction  with 
the  Bunsen's  water  air-pump;  in  the  other,  with  the  apparatus 
for  the  absorption  of  carbonic  acid  gas.  Its  lid  closes  air- 
tight by  means  of  a  mercurial  joint.      For  a  guineapig  or  rat, 


BY    DR.    BURDON-SANDERSON.  313 

it  should  have  a  capacity  of  about  500  cubic  inches  (8193  c.  c). 
Between  the  blower  and  the  chamber  is  interposed  a  flask  of 
about  6  oz.  capacity,  through  the  cork  of  which  two  tubes 
pass  ;  of  these,  one  is  prolonged  nearly  to  the  bottom  ;  the 
other,  the  exit  tube,  ends  just  below  the  under  surface  of  the 
cork.  This  flask  is  filled  with  pumice,  moistened  with  solu- 
tion of  potash.  In  this  way  the  chamber  is  supplied  with  a 
constant  and  perfectly  steady  stream  of  air,  free  from  carbonic 
acid.  As,  however,  the  quantity  of  air  supplied  by  the  blower 
is  much  larger  than  is  required,  it  must  be  diminished  by 
allowing  a  certain  quantity  to  waste.  For  this  purpose  a  T 
tube  is"  interposed  between  the  blower  and  the  potash  flask, 
the  stem  of  which  is  connected  by  an  India-rubber  tube  with 
a  kind  of  safety-valve,  the  construction  of  which  is  the  same 
as  that  of  valve  b,  in  fig.  251 ;  the  waste  of  air  may  be  in- 
creased or  diminished  by  raising  or  lowering  the  longer  of  the 
two  tubes.  The  absorbing  apparatus  consists  of  two  or  a 
greater  number  of  absorption  tubes  (fig.  252),  which  are 
charged  with  absorbing  liquid.  When  each  tube  is  placed  at 
its  proper  inclination,  and  the  difference  between  the  pressure 
on  opposite  sides  of  the  column  of  liquid  is  not  too  great,  the 
air,  which  enters  the  short  limb  by  an  end  of  India-rubber 
tube  which  reaches  nearly  to  the  bend,  passes  up  the  long  arm 
in  a  regular  succession  of  bubbles  so  small  that  it  is  thoroughly 
acted  on  b3r  the  liquid.  The  two  tubes  are  charged  with  a 
solution  of  baryta,  which  in  the  longer  is  three  times  as  strong 
as  in  the  shorter.  The  strengths  of  both  solutions  are  deter- 
mined volumetrically  by  a  standard  solution  of  oxalic  acid 
before  and  after  every  period  of  observation. 

Preparation  of  the  Solutions  of  Baryta  and  Oxalic  Acid. — 
Of  the  two  solutions  of  baryta  which  are  in  use,  the  stronger 
contains  about  21  grammes  of  hydrate  of  baryta  in  a  litre, 
the  other  7  grammes;  the  former  is  obtained  by  adding  suf- 
ficient distilled  water  to  420  cub.  cent,  of  saturated  baryta 
water  to  make  up  a  litre  ;  the  latter  contains  140  cub.  cent,  in 
a  litre.  These  liquids  must  be  kept  in  bottles  which  have  no 
communication  with  the  air,  excepting  through  a  flask  or  ab- 
sorption tube  filled  with  pumice,  moistened  with  potash.  The 
oxalic  acid  solution  must  be  prepared  with  the  utmost  accuracy. 
It  must  contain  2.8636  grammes  of  pure  well-crystallized 
oxalic  acid,  free  from  efflorescence,  in  a  litre.  Before  making 
the  solution,  it  is  necessary  to  dry  the  crystals  over  sulphuric 
acid  for  a  few  hours.  The  strength  of  this  solution  stands  in 
the  ratio  of  exactly  1  to  22  to  that  of  the  ordinary  volumetri- 
cal  solution  of  the  pharmacopoeia.  It  keeps  badly,  being  apt 
to  become  mouldy,  so  that  if  a  large  amount  is  required,  it 
is  better  to  keep  the  weighed  quantities  of  oxalic  acid  than  the 
liquid. 


314  RESPIRATION. 

Mode  of  determining  the  Strength  of  the  Baryta  Solution. — 
Thirty  centimetres  of  baryta  water  having  been   introduced 

into  a  small  flask,  the  solution  of  oxalic  arid  is  cautiously 
added  from  a  finely  graduated  burette.  Between  each  addi- 
tion, the  flask  is  closed  with  the  thumb  and  shaken.  As  an 
indicator,  Pettenkofer  has  found  that  turmeric  paper  gives 
better  results  than  litmus.  The  paper  must  be  prepared  by 
digesting  turmeric  root  in  weak  alcohol,  and  dipping  strips  of 
Swedish  filter  paper  into  it,  which  must  then  be  dried  in  a 
dark  place,  and  kept  in  the  dark.  "When  the  liquid  is  so  nearly 
neutralized  that  it  does  not  brown  a  strip  of  paper  dipped 
into  it,  a  drop  is  placed  with  a  rod  on  the  strip.  If  there  is 
still  a  trace  of  alkaline  reaction,  a  brown  line  appears  at  the 
periphery.  As  soon  as  this  is  no  longer  the  case,  the  point  of 
complete  neutralization  has  been  attained.  This  reaction  is  so 
delicate,  that  it  is  sensibly  affected  by  the  presence  of  one- 
tenth  of  a  cubic  centimetre  of  solution  of  oxalic  acid,  i.  e., 
one-tenth  of  a  milligramme  of  carbonic  acid  gas,  so  that  the 
results  of  two  determinations  of  the  same  liquid  ought  not  to 
differ  from  each  other  by  more  than  the  quantity  named.  It 
is  well,  in  order  to  save  time,  to  make  a  first  experiment  with 
a  small  quantity  (say  5  cub.  cent.).  It  is  of  great  practical 
importance  to  notice  that  the  baryta  solution  must  contain  no 
trace  of  caustic  potash,  or  soda,  the  smallest  quantities  of 
which  render  the  determination  impossible — for  the  oxalate  of 
potash  or  soda  formed  in  this  case  reacts  on  the  carbonate  of 
baryta  present,  so  as  to  produce  oxalate  of  baryta  and  carbo- 
nate of  soda.  Consequently,  the  liquid  never  loses  its  alkaline 
reaction,  for  each  renewed  addition  of  oxalic  acid  re-converts 
the  alkaline  carbonate  into  oxalate,  which  is  again  decomposed 
by  the  carbonate  of  baryta  as  before. 

Mode  of  preparing  and  filling  the  Absorption  Tubes. — Tfie 
short  arm  of  each  tube  is  filled  air-tight  with  an  India-rubber 
cork,  pierced  with  a  tube.  The  larger  tube  is  connected  at  its 
opposite  end  with  the  smaller,  from  which  the  air  finall}'  escapes 
through  an  India-rubber  tube,  guarded  by  a  screw-clip.  By 
adjusting  this  clip,  the  size  of  the  bubbles  is  regulated,  their 
magnitude  varying  inversely  as  the  resistance.  To  fill  the 
tubes,  the  required  quantities  of  liquid  are  introduced  into 
flasks,  fitted  with  air-tight  corks,  having  necks  sufficiently  wide 
for  the  introduction  of  a  pipette.  The  strength  of  the  solution 
having  been  determined  in  thirty  centimetres,  as  above  de- 
scribed, the  stronger  solution  is  to  be  delivered  into  the  first 
absorption  tube  in  three  quantities  of  45  centimetres,  and  two 
such  quantities  of  the  weaker  into  the  second.  [Tubes  of  the 
size  required  for  these  quantities  are  made  by  Cetti  &  Co., 
of  Brooke  Street,  Holborn.]  The  tubes  are  then  closed  and 
adjusted  to  the  proper  inclination  (previously  ascertained  by 


BY    DR.    BURD0N-5ANDERS0X.  315 

trial).  At  the  close  of  the  experiment,  the  liquids  are  trans- 
ferred once  more  to  flasks,  similar  to  those  above  described,  and 
their  strength  determined  as  before.  The  calculation  of  the 
result  is  simple.  The  quantity  of  carbonic  acid  absorbed  by 
each  30  cub.  cent,  of  the  liquid  is  indicated  by  the  difference 
between  the  corresponding  quantities  of  oxalic  acid  solution 
used,  before  and  after  absorption.  This  quantity  must  be  mul- 
tiplied in  the  one  case  by  133q5  =  4.5,  in  the  other  by  f£=3.  The 
sum  of  the  two  products  is  the  total  quantity  of  carbonic  acid 
disengaged  during  the  period  of  observation.  If  an  animal 
larger  than  a  guineapig  is  used,  it  is  necessary  to  employ  two 
sets  of  absorbing  tubes,  or  a  greater  number. 

Section  V. — Innervation  of  the  Respiratory  Movements. 

The  rhythmical  movements  of  respiration  depend  on  the 
activity  of  a  centre  contained  in  that  part  of  the  floor  of  the 
fourth  ventricle  from  which  the  roots  of  the  vagus  nerve 
spring.  The  proof  of  this  fact  lies  in  the  fundamental  ex- 
periment of  Legallois,  by  which  he  showed  that  the  cerebrum, 
the  cerebellum,  and  even  part  of  the  medulla  oblongata  itself 
may  be  removed,  without  arresting  respiration.  This  experi- 
ment has  already  been  described  in  §  92. 

By  motor  nerves  this  centre  is  in  relation  with  the  muscles 
of  which  the  combined  rhythmical  actions  have  been  studied  in 
the  same  paragraph.  Its  discharges  of  energ}',  like  those  of 
the  motor  centres  of  the  heart,  are  automatic,  but  their  rhythm 
is  constantly  subject  to  modification  by  impressions  received 
through  the  afferent  fibres  of  the  vagi.  Consequently,  the  study 
of  the  innervation  of  the  respiratory  movements  resolves  itself 
into  experiments  relating  to  the  respiratory  functions  of  these 
nerves.  The  results  of  such  experiments  ma}*  be  divided  accord- 
ing as  they  relate  to  the  effects  of  section  of  both  vagi,  to  ex- 
citation of  the  central  end  of  the  divided  nerves,  or  to  excita- 
tion of  the  superior  laryngeal  nerve. 

99.  Section  of  both  Vagi  in  the  Neck. — In  the  para- 
graph relating  to  the  functions  of  the  vagus  as  a  heart-nerve, 
directions  have  been  given  as  to  the  mode  of  preparing  it.  The 
rabbit  is  preferable  to  the  dog  or  cat,  for  in  those  animals  the 
vagus  is  united  in  one  trunk  with  the  sympathetic.  Section 
of  the  vagi  is  the  simplest  and  at  the  same  time  one  of  the  most 
instructive  experiments  relating  to  the  physiology  of  the  ner- 
vous system.  The  animal  having  been  secured  in  the  usual 
way  on  Czermak's  rabbit  support,  a  ligature  is  passed  round 
each  nerve  a  little  below  the  cricoid  cartilage.  The  ends  of 
each  ligature  are  then  knotted  together,  so  as  to  facilitate  their 
being  found  at  any  moment.  To  observe  the  effect,  the  animal 
should  be  placed  before  and  after  section,  under  the  same  cir- 


316  RESPIRATION. 

cumstances.  If  it  is  not  intended  to  record  the  results  graphi- 
cally, it  may  be  allowed  to  run  about  while  the  respirations  arc 
counted,  and  careful  observations  are  made  as  to  the  respira- 
tory movements.  For  more  exact  observations  various  methods 
may  be  used,  each  of  which  is  of  some  value.  The  first  consists 
in  recording  the  movements  of  the  diaphragm  on  the  kymo- 
graph, as  directed  in  §  91.1  The  second  and  third  are  so  con- 
trived as  to  show  not  only  the  duration  and  rhythm  of  the 
respiratory  movements  before  and  after  section,  but  the  extent  of 
the  respiratory  exchange  of  air.  The  apparatus  for  this  purpose 
is  constructed  as  follows:  A  large  bottle,  capable  of  holding 
five  gallons  or  more,  is  closed  air-tight  with  an  India-rubber 
cork,  into  which  the  stem  of  a  glass  "|"  tube  is  carefully  fitted. 
Of  the  two  branches  of  the  T  tube,  one  communicates  with  the 
respiratory  cavity  of  the  animal,  by  a  connector  of  India-rub- 
ber and  a  glass  canula  secured  air-tight  in  the  trachea,  the  other 
is  left  open  and  can  be  readily  closed  with  the  finger.  The 
bottle  also  communicates  by  a  second  glass  tube  which  passes 
through  its  India-rubber  stopper,  with  a  Marey's  tympanum, 
the  lever  of  which  writes  on  the  blackened  cylinder  of  the  k}'mo- 
graph.  This  tube  is  controlled  by  a  screw  clamp.  So  long  as 
the  arm  of  the  T  piece  is  left  open,  the  animal  of  course  breathes 
the  external  air  freely.  On  placing  the  finger  against  the  aper- 
ture, it  begins  to  breathe  the  air  of  the  bottle,  but  inasmuch  as 
the  capacity  of  this  vessel  is  250  times  as  great  as  the  respira- 
tory cavity  of  the  rabbit,  it  can  do  so  for  some  time  without 
the  slightest  dyspnoea,  as  is  proved  by  the  observation  that  the 
depressors  of  the  larynx  do  not  come  into  action.  The  resist- 
ance is,  however,  sufficiently  great  to  affect  the  lever  of  the 
tj'mpanum,  the  rise  and  fall  of  which  in  each  respiratory  act  is 
in  exact  proportion  to  the  quantity  of  air  breathed.  The  animal 
having  been  chloralized  and  both  nerves  prepared  as  above  de- 
scribed, a  few  tracings  should  be  taken  of  the  normal  respira- 
tion. This  done,  the  clockwork  is  again  set  in  motion  and  botli 
nerves  are  divided  at  the  same  moment.  In  this  way  a  tracing 
(fig.  253)  is  obtained,  which  strikingly  exhibits  the  effects  of 
section,  both  as  regards  the  rhythm  and  extent  of  the  thoracic 
movements. 

Another  method  consists  in  measuring  the  quantity  of  air 
inspired  in  a  given  time  with  the  aid  of  the  apparatus  shown 
in  fig.  251.  In  this  way  the  effect  of  section  on  the  respiratory 
exchange  can  be  estimated  with  much  greater  precision  than 
in  any  other,  but  obviously  no  information  is  obtained  as  to 
the  respiratory  movements. 

100.  The  most  important  results  are  as  follows:   1.  In  the 

1  The  tracing  so  obtained  is  shown  in  the  first  (normal)  part  of  fig. 
255. 


BY    DR.    BURDON-SANDERSON.  317 

adult  rabbit,  the  number  of  respirations  per  minute  diminishes 
from  120—140  to  40—50.     That  this  is  only  to  a  very  slight 
extent  dependent  on  the  narrowing  of  the  glottis  due  to  the 
relaxation  of  the  intrinsic  muscles  of  the  larynx,  is  proved  by 
the  fact  that  if  the  two  recurrents  are  divided,  the  retarding 
effect  of  the  operation   is  very  inconsiderable,  while  the   re- 
tarding effect  of  section  is  diminished  in  no  appreciable  degree 
by  previous  tracheotom}\     2.  The  mechanism  of  breathing  is 
completely  altered.     Each  respiration  is  about  five  times  as 
deep  as  it  was  before.    This  depends  partly  on  increased  action 
of  the  diaphragm,  partly  on  the  participation  of  the  accessory 
muscles  in  the  inspiratory  act.     The  belly  is  projected  and  the 
larynx  drawn  down  by  the  sternal  muscles  in  each  inspiration, 
while  the  upper  ribs,  which  before  were  motionless,  are  drawn 
upwards  and  outwards  by  the  external  intercostals  and  inter- 
cartilaginous    muscles.      The   inspiratoiy   expansion    of   the 
upper  part  of  the  thorax  lasts  for  several  seconds,  at  the  end 
of  which   it   suddenly  collapses,  expelling  the  air  with  such 
force  as  to  make  an  audible  sonorous  noise  in  the  air-passages, 
often  accompanied,  if  the  trachea  has  not  been  opened,  with 
a  coarse  rale.     This  sudden  collapse,  which  is  a  non-muscular 
act,  is  followed  by  a  long  pause,  the  existence  of  which  is 
characteristic.     At  the  end  of  it  there  usually  occurs  a  short 
expiratory  movement,  attended  with  hardening  of  the  muscles 
of  the  abdominal  wall,  which  is  the  immediate  precursor  of  the 
inspirator}7  act.     The  mode  of  breathing  just  described  is  that 
of  dyspnoea;  but  there  is  this  important  difference  between 
ordinary  dyspnoea  and  that  produced  by  section  of  the  vagi, 
that  whereas  in  the  former  the  frequency  of  the  respiratory 
movements  is  increased,  in   the  latter  it  is  diminished  ;  with 
this  exception,  all  the  characteristics  of  dyspnoea  are  present. 
3.  The  quantity  of  air  breathed  per  minute  is  as  great  after 
section  of  both  vagi  as  before,  the  diminished  frequency  of 
the  respirations  being  counterbalanced  Irv  the  increased  depth 
of   the   respiratory  act.      This  is  proved   by  measuring  the 
quantity  of  air  breathed  in  a  given  time  in  the  manner  above 
directed.      4.    These  facts  afford    ground  for  inferring    that 
although  section  of  both  vagi  does  not  materially  either  in- 
crease or  diminish  the  work  done  in  a  given  time  by  the  re- 
spiratory muscles,  it  interferes   very   considerably  with   the 
accomplishment  of  the  purpose  of  their  movements — the  ar- 
terialization  of  the  blood.     Notwithstanding  the  vigor  of  the 
respiratory  movements,  the  blood  becomes  more  or  less  venous. 
101.   Death  after  Section  of  both  Vagi. — Rabbits  in 
which  both  vagi  have  been  divided,  commonly  die  before  the 
end  of  the  first  day.     Dogs  live   longer — often   two  or  three 
days.     After  death,  the  lungs  are  found  in  an  altered  condi- 
tion, of  which  the   following  are  the   leading   features:    The 


318  RESPIRATION. 

mucous  lining  of  the  air-passages  is  reddened  (especially  in 
dogs),  the  color  being  due  to  the  injection  of  the  capillaries  of 
the  mucosa  with  blood.  The  lungs  collapse  much  less  than 
naturally  when  the  chest  is  opened.  The  pulmonary  paren- 
chyma is,  to  a  greater  or  less  extent,  devoid  of  air.  The  air- 
less parts  are  soaked  with  a  brownish-red  serous  liquid,  and 
here  and  there  choked  with  a  grayish-white  material,  which,  on 
microscopical  examination,  is  found  to  consist  of  young  cells 
(pus  corpuscles).  Similar  cells  are  seen  in  the  serous  liquid 
along  with  numerous  blood  corpuscles.  These  changes  may 
be  accounted  for  as  follows:  When  the  vagi  are  divided,  all 
the  parts  to  which  the  branches  below  the  point  xof  section  are 
distributed  are  affected,  e.  g.,  the  larynx,  air-passages,  lungs, 
oesophagus,  etc.  1.  The  glottis  is  partially  closed,  just  as  it  is 
after  death.  2.  The  mucous  lining  of  the  air-passages  is  de- 
prived of  sensibility,  so  that,  when  it  is  irritated,  no  cough  is 
produced.  3.  The  muscular  fibres  of  the  oesophagus  are  para- 
lyzed, so  that  regurgitation  of  food  from  the  stomach  is  apt 
to  take  place;  the  muscular  fibres  of  the  bronchial  tubes  are 
in  a  similar  condition.  With  reference  to  these  co-efficients  in 
the  production  of  the  lung  affection  we  have  the  following 
facts,  showing  that  the  first  two  are  at  all  events  the  only  ones 
which  are  of  importance:  (a)  A  lung  affection  of  the  same 
nature  as  that  induced  by  section  of  both  vagi,  though  of  in- 
ferior intensity,  follows  section  of  the  inferior  laryngeal 
nerves,  (b)  In  animals  with  divided  vagi,  life  is  prolonged 
by  tracheotomy,  the  degree  of  prolongation  depending  on  the 
efficiency  of  means  used  to  prevent  the  entrance  of  foreign 
bodies  into  the  air-passages,  (c)  In  animals  of  which  the  vagi 
are  intact,  a  lung  affection  is  produced  b}'  injecting  mucus 
from  the  pharynx  into  the  air-passages  which  is  of  the  same 
nature  with  that  now  under  consideration.  The  combination 
of  these  facts  leads  to  the  inference  that  the  inflammation  of 
the  lungs  of  which  animals  with  divided  vagi  die,  is  dependent 
on  the  intrusion  of  foreign  bodies  from  the  pharynx  into  the 
air  passages  and  lungs,  rather  than  to  an}'  direct  effect  of  the 
section  on  the  lung  tissue. 

102.  Demonstration  of  the  Respiratory  Functions 
of  Afferent  Fibres  of  the  Vagus,  by  Excitation  of  the 
Central  End  of  the  Divided  Nerve. — The  method  of 
preparing  the  nerve  has  been  already  described.  The  excitor, 
shown  in  fig.  225,  is  used.  It  is  better  to  employ  Helmholtz's 
side  wire  (see  next  paragraph),  but  not  necessary  ;  for  even 
when  strong  unmodified  induced  currents  are  used,  there  is 
little  danger  of  unipolar  effects,  the  extent  to  which  the  nerve 
can  be  separated  being  such,  that  there  is  no  difficulty  in  inter- 
posing a  considerable  air  space  between  it  and  the  surrounding 
parts. 


BY    DR.    BURDON-SANDERSON.  319 

The  phenomena  which  accompany  excitation  of  the  central 
end  of  the  divided  vagus  vary  according  to  the  state  of  the 
animal  and  the  state  of  the  nerve.  It  will  be  convenient  to 
describe  them  under  heads  corresponding  to  these  conditions: 
1.  Animal  breathing  naturally.  To  observe  what  may  be  re- 
garded as  the  normal  results  of  excitation,  care  must  be  taken 
that  the  subject  of  experiment  is  not  exhausted,  and  that,  in 
placing  it  on  the  support,  nothing  is  done  which  can  interfere 
with  its  breathing.  The  movements  of  the  diaphragm  must 
be  recorded1  either  with  the  aid  of  the  apparatus,  fig.  250,  or 
in  the  manner  described  in  the  preceding  paragraph  ;  but  for 
the  present  purpose,  by  far  the  best  method  is  to  introduce 
into  the  peritonaeal  cavity,  by  means  of  a  small  opening  in  the 
linea  alba  close  to  the  ensiform  cartilage,  a  small  flat  bag  of 
India-rubber,  of  such  size  that  it  can  be  conveniently  slipped 
between  the  diaphragm  and  liver.  If  this  bag  is  slightly  dis- 
tended with  air  and  connected  with  a  Marey's  tj'mpanum,  it 
gives  excellent  tracings  of  the  diaphragmatic  movements.  To 
the  student  who  witnesses  the  experiment  for  the  first  time,  a 
still  more  convincing  mode  of  appreciating  the  effect  of  ex- 
citing the  central  end  on  the  diaphragm  is  to  feel  the  con- 
traction of  the  muscle  with  the  finger  during  the  period  of  ex- 
citation. The  nerve  having  been  prepared,  and  the  excitor 
placed  under  it,  a  preliminary  tracing  must  be  taken  of  the 
normal  respiration.  In  a  tracing,  taken  by  the  method  de- 
scribed in  §  99,  it  is  seen  that  in  each  respiratory  act  three  parts 
may  be  distinguished,  one  of  which,  the  ascent,  expresses  in- 
spiration, or  active  contraction  of  the  diaphragm  ;  the  whole 
of  the  remainder  of  the  period  corresponds  to  relaxation  or 
that  muscle.  Sometimes  the  part  of  the  curve  which  imme- 
diately precedes  the  ascent  indicates  that  towards  the  close  of 
the  period  of  relaxation  air  neither  enters  nor  leaves  the  chest. 
If  a  straight  line  is  drawn  through  the  angle  formed  in  each 
curve  at  the  point  corresponding  to  the  commencement  of  in- 
spiration, it  ma}'  be  taken  as  indicating  the  position  of  the 
lever  when  the  diaphragm  is  at  rest  after  an  ordinary  expi- 
ration. So  long  as  air  is  passing  out  of  the  chest,  the  lever 
keeps  below  this  line,  but  as  soon  as  the  outflow  ceases,  pro- 
vided that  the  diaphragm  is  still  relaxed,  it  returns  to  it. 
Hence  the  line  corresponds  to  the  position  of  equilibrium. 
These  facts  are  well  seen  in  the  first  (normal)  part  of  tracing, 
fig.  255. 

The  tympanum  having  now  been  connected  with  the  bag 
between  the  diaphragm  and  liver,  as  above  described,  and  the 
secondary  coil  placed  at  a  considerable  distance  from  the  pri- 
mary, the  key  which  has  been  connected  with  the  telegraph  is 

1  See  fig.  254a. 


320  RESPIRATION. 

opened.  The  effect  cannot  be  predicted  with  certainty. 
Probably  the  respiratory  movements  will  be  quickened,  the 
lever  assuming  a  somewhat  higher  position  during  the  period 
of  excitation  than  it  did  before.  This  indicates  that  the  dia- 
phragm descends  further  in  each  inspiration,  and  does  not 
relax  quite  so  much  in  expiration. 

The  secondary  coil  must  now  be  gradually  brought  up 
nearer,  while  the  excitation  is  repeated  after  each  shifting, 
until  it  is  observed  that  the  lever  ascends  and  remains  station- 
ary each  time  the  key  is  opened,  drawing  a  nearly  horizontal 
line  at  a  much  higher  level  than  that  of  the  previous  part  of 
the  tracing.  (See  fig.  254  &.')  If  the  excitation  is  continued 
only  for  a  few  seconds,  the  elevation  of  the  lever  which  indi- 
cates contraction  of  the  diaphragm  not  only  continues  during 
the  whole  time,  but  lasts  a  second  or  two  after  it.  The  lever 
then  gradually  falls,  and  after  a  few  moments  resumes  its  up- 
and-down  movements,  always  beginning  with  a  descent.  In 
other  words,  the  diaphragm,  after  a  period  of  contraction, 
which  somewhat  exceeds  its  cause  in  duration,  is  for  a  moment 
relaxed  before  it  assumes  its  rhythmical  action.  The  conduct 
of  the  other  respiratoiy  muscles  should  be  carefully  watched 
(by  another  observer)  during  these  experiments.  It  will  be 
seen  that,  provided  that  the  animal  is  breathing  perfectly 
naturally  at  the  moment  that  the  key  is  opened,  the  descent 
of  the  diaphragm  determined  by  the  excitation  of  the  vagus 
is  not  attended  by  any  other  muscular  movement,  and  in  par- 
ticular, that  the  upper  ribs  remain  as  motionless  as  before, 
and  that  the  larynx  does  not  descend.2  2.  Animal  in  the 
state  of  apneea.  In  a  rabbit  of  which  the  blood  has  been  sur- 
charged with  oxygen  by  excessive  artificial  respiration,  the 
effect  of  exciting  the  central  end  of  the  vagus  is  negative. 
No  respiratory  movement  is  produced.  To  demonstrate  this, 
experiments  must  be  made  before,  during,  and  after  apnoea. 
It  is  found  that  the  same  current  which  tetanizes  the  dia- 
phragm in  the  normal  state,  has  no  effect  when  the  blood  is 
over-arterialized.  This  is  an  experiment  of  fundamental  im- 
portance, because  it  shows  that  the  relation  between  the  vagus 

1  Fig.  2545  shows  that  during  the  whole  period  of  excitation  (indi- 
cated by  the  horizontal  line  below)  the  diaphragm  remained  contracted  ; 
then  followed  a  few  irregular  movements,  after  which  the  rhythmical 
movements  were  resumed  with  a  slightly  increased  frequency.  The 
period  of  contraction  was  interrupted,  as  frequently  happens,  by  a 
momentary  relaxation. 

2  Fig.  254a  was  obtained  in  the  same  animal  as  2546  with  the  aid  of 
the  apparatus,  Fig.  250.  The  tracing  shows  that  the  rhythmical  move- 
ments were  not  resumed  until  a  second  or  two  after  excitation  had 
ceased.  They  were  at  first  somewhat  more  frequent  than  before,  and 
the  diaphragm  was  in  a  lower  position.  In  less  than  a  minute  the  pre- 
vious conditions  were  restored  in  both  respects. 


BY   DR.    BURBON-SANDERSON.  321 

and  the  motor  nerves  of  respiration  (and  particularly  the 
phrenic)  is  entirely  different  from  that  which  exists  between 
the  afferent  and  efferent  nerve  in  the  ordinary  case  of  reflex 
action.  3.  Animal  in  the  state  of  dysjmoea.  When  the  blood, 
instead  of  containing  too  much  oxygen,  contains  too  little,  the 
effect  of  excitation  of  the  central  end  extends  itself  to  all  the 
extra  muscles  which  are  at  the  time  in  action  ;  consequently, 
J;he  greater  the  dyspnoea,  the  greater  is  the  number  of  muscles 
which  respond  to  the  stimulus.  This  is  best  seen  in  an  animal 
in  which  after  perforation  of  one  side  of  the  chest,  respiration 
is  maintained  artificially  ;  the  same  rabbit  which  has  served 
for  the  other  experiments  may  be  used.  The  result  may  be 
varied  according  to  the  degree  of  dyspnoea  produced,  by  regu- 
lating the  frequency  and  quantity  of  the  injections  of  air.  If, 
for  example,  the  dj'spncea  is  sufficient  to  bring  into  action  the 
external  intercostals,  intercartilaginei,  and  scaleni,  all  these 
muscles  contract  simultaneously  with  the  diaphragm  when  the 
central  end  is  excited,  so  that  the  chest  remains  during  the 
time  that  the  key  is  open,  in  a  state  of  tetanic  expansion. 

103.  Excitation  of  the  Central  End  of  one  Vagus  after  Sec- 
tion of  both. — By  very  careful  graduation  of  the  induced  cur- 
rent (with  Helmholtz's  modification),  it  is  sometimes  possible 
to  supply  the  precise  degree  of  excitation  to  the  vagus  centre, 
which  is  required  to  make  up  for  the  loss  sustained  by  the  sec- 
tion of  its  afferent  fibres,  and  in  this  way  to  restore  the  normal 
respiratory  rhj'thm.  More  frequently  the  experiment  fails, 
and  effects  are  produced  which  correspond  to  those  described 
above. 

Exceptional  Cases. — It  very  frequently  happens,  particularly 
in  animals  under  the  influence  of  chloral,  that  effects  are  pro- 
duced by  excitation  of  the  central  end  which  are  just  the  oppo- 
site of  those  whic,h  we  regard  as  normal.  The  diaphragm,  in- 
stead of  contracting,  relaxes,  and  remains  relaxed  during  the 
whole  time  (see  Fig.  255')  that  the  key  is  open.  The  imme- 
diate cause  of  this  generally  is  that  the  nerve  is  exhausted. 
The  reason  why  it  happens  is  that  the  vagus  contains  (in  addi- 
tion to  the  fibres  which,  when  excited,  act  on  the  vagus  centre 
in  such  a  way  as  to  lessen  the  hypothetical  resistance  by  which 
it  is  normally  prevented  from  discharging  itself  in  muscular 
contractions)  other  fibres,  which  in  the  language  of  physiolo- 

1  The  tracing,  Fig.  2o.r>,  was  obtained  by  the  method  described  in 
U  90.  During  the  whole  period  of  excitation  the  diaphragm  remained 
stationary  in  the  position  of  ordinary  expiration  ;  almost  immediately 
after,  the  rhythmical  movements  were  resumed,  the  first  movement  be- 
ing an  ordinary  inspiration.  The  period  was  interrupted  by  a  single 
respiratory  movement,  caused  by  the  accidental  removal  of  the  elec- 
trodes from  the  nerve.  The  notches  in  the  horizontal  part  of  the  tracing 
express  cardiac  pulsations. 
21 


322  RESPIRATION. 

gists  arc  "inhibitory" — t. c,  tend  to  increase  the  resistance 
above  referred  to.  In  the  fresh  state  of  the  nerve,  the  influ- 
ence of  these  fibres  is  completely  overbalanced  by  that  of  the 
others.  In  the  exhausted  state,  this  relation  is  reversed,  so 
that  the  two  sets  of  afferent  fibres  are  as  much  distinguished 
from  each  other  by  their  difference  of  endurance  as  by  their 
differences  of  function.  Recent  experiments  (Burkhart)  make 
it  probable  that  the  "inhibitory"  fibres  come  mostly  from  the 
recurrents. 

104.  Excitation  of  the  Superior  Laryngeal  Nerve. — 
The  experimental  investigation  of  the  superior  laryngeal  is 
much  more  difficult  than  that  of  the  trunk  of  the  vagus,  partly 
because  the  nerve  is  difficult  to  reach  and  runs  a  short  course, 
partly  because  it  is  very  slender.  To  expose  it  in  the  rabbit, 
an  incision  should  be  made  extending  from  the  side  of  the  tra-. 
chea,  at  the  level  of  its  first  and  second  rings,  to  the  hollow 
between  the  angle  of  the  jaw  and  the  laiynx.  After  severing 
the  skin  in  the  usual  way,  the  fascia  which  extends  forwards 
from  the  edge  of  the  sterno-mastoid  muscle  must  be  carefully 
broken  through  with  the  aid  of  two  pairs  of  dissecting  forceps, 
so  as  to  expose  the  parts  seen  in  Fig.  227.  The  space  is  di- 
vided into  two  by  the  artery,  the  direction  of  which  coincides 
exactly  with  that  of  the  original  incision.  Near  its  lower  end 
the  arteiy  gives  off  its  thyroid  branch.  At  the  top  the  space 
is  limited  by  the  tendon  of  the  stylohyoid  muscle,  and  the  pos- 
terior cornu  of  the  hyoid  bone.  Immediately  below  the  muscle 
is  the  trunk  of  the  ninth  nerve,  which  arches  forwards  towards 
the  tongue.  The  descending  branch  of  that  nerve  passes  down- 
wards and  forwards  to  reach  the  muscles  which  cover  the  front 
of  the  trachea,  giving  communicating  branches  to  the  cervical 
plexus,  and  a  branch  which  arches  forwards  over  the  artery  to 
gain  the  muscles  which  draw  the  larynx  upwards.  Before  pro- 
ceeding to  expose  the  deeper  nerves,  it  is  well,  in  order  to  avoid 
confusion,  to  remove  the  descendens  noni;  the  next  step  is  to 
draw  the  larynx  well  to  the  side  opposite  to  that  chosen  for 
the  incision,  so  as  to  widen  the  space  between  it  and  the  caro- 
tid artery.  This  done,  the  exposure  of  the  superior  laryngeal 
becomes  eas}-.  Its  exact  position  is  indicated  in  the  figure  ;  its 
course  is  much  twisted,  so  as  to  allow  of  the  up-and-down 
movements  of  the  laiynx.  In  preparing  it,  no  cutting  instru- 
ments must  be  used.  It  must  be  freed  from  the  surrounding 
structures  with  the  aid  of  two  pairs  of  forceps,  any  veins  in 
the  way  having  been  divided  between  two  ligatures.  Care 
must  be  taken,  however,  to  leave  a  certain  quantity  of  cellular 
tissue  about  it  to  serve  as  a  kind  of  protective  sheath,  and 
make  it  somewhat  less  liable  to  get  dry.  The  nerve  having 
been  prepared,  a  ligature  must  be  tied  round  it  as  near  as  pos- 
sible to  the  thyrohyoid  membrane,  after  which  it  must  be  di- 


BY  DR.  BURDON-S ANDERSON.  323 

vided  beyond.  In  the  dog  or  cat  the  mode  of  preparation  is 
very  much  the  same  as  in  the  rabbit.  In  the  cat,  the  compara- 
tive thickness  of  the  nerve  facilitates  the  manipulation. 

In  exciting  the  superior  laryngeal,  the  great  source  of 
difficulty  is  the  proximity  of  the  vagus  and  the  consequent 
liability  of  that  nerve  to  be  acted  on  by  the  induced  current 
in  a  unipolar  way.  This  accident,  which  is  of  course  fatal  to 
the  success  of  the  investigation,  the  functions  of  the  two 
nerves  being  opposite,  is  to  be  avoided,  not  by  the  use  of 
complicated  arrangements  for  the  insulation  of  the  nerve,  but 
b}-  placing  it  in  such  a  way  on  the  ordinary  copper  points  that 
the  part  acted  on  is  separated  by  a  considerable  air  space  from 
the  surrounding  tissues.  Before  beginning  the  excitation,  the 
secondary  coil  must  be  shifted  to  a  distance  from  the  primary, 
and  the  primary  current  divided  by  means  of  Helmholtz's  side 
wire  into  two  branches,  one  of  which  only  passes  through  the 
breaker.  The  other  is  led  directly  from  the  battery  to  the  coil, 
so  that  the  primary  current  is  never  entirely  opened.  In  this 
way  the  opening  induction  shock,  which,  in  the  ordinary 
arrangement  of  the  induction  apparatus,  possesses  a  much 
greater  tension  than  that  of  the  closing  shock,  is  so  reduced 
that  the  two  become  nearly  equal  to  each  other.'  Conse- 
quently, as  the  risk  of  unipolar  action  varies  with  the  maxi- 
mum intensity  of  the  current,  it  is  very  much  diminished  by 
this  contrivance — so  much  so,  indeed,  that  if  care  is  taken  to 
prepare  the  nerve  properly,  even  nioderateby  strong  currents 
ma}'  be  used  without  any  effects  referable  to  unipolar  excita- 
tion of  the  vagus  manifesting  themselves.  Excitation  of  the 
central  end  of  the  superior  laryngeal  produces,  according  to 
the  strength  of  the  current  used,  either  diminution  of  fre- 
quency of  the  respiratory  movements  or  complete  relaxation 
of  the  muscles  of  inspiration.  The  most  advantageous  way 
of  judging  of  its  effect  on  the  diaphragm,  is  to  expose  that 
muscle  in  the  way  directed  in  §  91.  It  is  then  seen  that  that 
muscle  becomes  absolutely  flaccid  during  excitation  of  the 
nerve,  and  it  is  drawn  up  by  the  elastic  contraction  of  the 
lungs,  so  as  to  assume  its  highest  possible  position.  When 
the  excitation  is  discontinued,  the  relaxation  either  gives  way 
to  natural  breathing  or  is  immediately  succeeded  by  one  or 
two  vigorous  inspirations.  If  the  current  is  so  feeble  that  it 
merely  diminishes  the  frequency  of  the  respirations,  without 
arresting  them,  the  tracings  show  that  there  is  no  diminution 
of  the  duration  of  the  inspiratory  acts,  and  that  the  slowing 
is  entirely  due  to  a  prolongation  of  the  intervals,  i.  e.,  of  the 

1  For  a  fuller  explanation  of  the  difference  between  the  two  induced 
currents  and  of  the  effect  of  Helmholtz's  modification,  see  Rosenthal, 
"Electricitatslehre,"  p.  120. 


324  RESPIRATION. 

periods  during  which  the  diaphragm  remains  in  the  position 
assumed  by  it  at  the  elose  of  ordinary  expiration.  To  record 
the  effects  graphically,  any  of  the  methods  recommended  in 
the  preceding  paragraphs  may  be  used.  If  the  method  de- 
scribed in  §  99  is  employed,  a  tracing  is  obtained  which 
exactly  resembles  fig.  255.  The  tracing,  fig.  250, '  was  drawn 
by  inserting  a  bag  between  the  diaphragm  and  the  liver. 

Section  VI. — Influence  of  the  Respiration  on  TnE  Circulation. 

105.  If  the  stethoscope  is  applied  to  the  prsecordia  of  a  dog, 
it  is  easity  observed,  especially  if  the  animal  has  been  narco- 
tized, that  the  rate  at  which  the  contractions  of  the  heart 
succeed  each  other  is  subject  to  rhythmically  recurring  varia- 
tions, and  that  the  acceleration  follows  each  expansion  of  the 
chest,  lasting  during  the  first  part  of  the  succeeding  expiration  ; 
while  during  the  latter  part  of  the  expiratory  period — the 
period  during  which,  as  we  have  seen,  air  is  expelled  very 
slowl}r — the  diastolic  intervals  become  longer.  These  facts 
admit  of  much  more  precise  demonstration  by  the  graphic 
method.  For  this  purpose  the  most  convenient  instrument  is 
that  shown  in  fig.  257. 

It  is  a  kymograph  so  constructed  as  to  record  the  arterial 
pressure  and  respiratory  movements  simultaneously.  The 
mercurial  manometer  consists  of  two  limbs  of  equal  length, 
one  of  which,  the  distal  (A),  is  much  wider  than  the  other 
near  the  top,  the  relation  between  the  lumen  of  the  one  and 
that  of  the  other  being  1 :  10.  The  float  wdiich  rests  on  the 
distal  column  is  of  boxwood.  Its  under  surface  is  concave,  so 
as  to  fit  the  convex  surface  of  the  mercury.  By  the  vertical 
rod  it  is  connected  with  a  light  lever,  d,  about  two  feet  in 
length,  which  is  counterpoised  by  a  weight  suspended  to  it  on 
the  other  side  of  the  brass  bearing,  e.  At  its  thin  end,  the 
lever  carries  a  pen,  the  distance  of  which  from  d  is  such,  that 
for  every  inch  of  variation  of  difference  between  the  two  col- 
umns of  the  manometer,  it  rises  or  falls  three-tenths  of  an 
inch.  It  will  be  readily  understood  that  the  movement  of  the 
pen,  instead  of  being  rectilinear,  is  circular;  consequently,  it 
is  vertical  only  when  the  lever  is  horizontal ;  for  which  reason 
the  fulcrum,  e,  which  is  so  constructed  as  to  slide  up  and  down 
on  the  brass  uprights,  must  alwa}^  be  placed  in  such  a  posi- 
tion that  the  lever  is  horizontal.     The  height  of  the  mercurial 

1  The  tracing,  fig.  256,  shows  that  during  the  whole  period  of  excita- 
tion the  diaphragm  remained  motionless  in  the  position  of  expiration, 
with  the  exception  that  at  gradually  lengthening  intervals  it  executed 
momentary  contractions.  When,  after  the  cessation  of  excitation,  the 
respiratory  movements  were  resumed,  they  were  slower  hut  more  ex- 
tensive than  before. 


BY   DR.    BURDON-SANDERSON.  325 

column  corresponds  to  the  average  arterial  pressure.  That 
part  of  the  instrument  which  is  intended  for  recording  the  re- 
spiratory movements,  consists  of  a  Marey's  tympanum,  c,  and 
a  lever,  F,  similar  to  D,  and  of  the  same  length,  with  which  it 
is  connected.  The  tube,  H,  of  the  tympanum  may  be  either 
brought  into  communication  with  one  arm  of  a  glass  T  tube, 
the  stem  of  which  is  inserted  in  the  trachea,  or  with  a  stetho- 
meter  applied  to  the  chest.  The  lever  of  the  tympanum  is 
connected  with  the  recording  lever  by  a  vertical  rod  seen  in 
the  drawing.  In  this  way  two  tracings  are  obtained  simul- 
taneously, of  which  fig.  258  is  an  example.  The  arterial  trac- 
ing is  marked  A  p,  the  respiratory  r.  In  the  latter,  the  begin- 
ning of  inspiration  is  indicated  by  the  vertical  stroke  a;  of 
expiration  by  b;  of  the  pause  b}'  c.  The  coincident  points  in 
A  P  are  indicated  by  similar  strokes.  The  break  is  made  by 
removing  both  pens  from  the  paper  by  the  same  act.  In  man, 
the  variations  of  frequenc}'  (which,  of  course,  can  alone  be  in- 
vestigated) are  absent  in  most  healthy  persons,  although  very 
obvious  in  certain  conditions  of  disease.  In  the  rabbit  they 
are  much  less  marked  than  in  the  dog.  They  are  regarded  by 
most  physiologists  as  dependent  on  variations  of  activity  of 
the  intracranial  centre  of  the  cardiac  vagus:  until  very  re- 
cently it  has  been  assumed,  by  way  of  explanation,  that  the 
respiratory  movements  affect  the  cerebral  circulation  in  such  a 
way  that  during  the  period  of  relaxation  of  the  muscles  of 
respiration,  the  supply  of  blood  to  the  medulla  oblongata  is 
diminished,  and  increased  during  their  contraction — and  that 
the  inhibitory  nervous  system  of  the  heart  is  affected  by  these 
changes.  This  explanation  has  always  appeared  unsatisfactory, 
and  could  only  be  accepted  provisionally;  for  it  seemed  ex- 
tremely improbable  that  there  was  any  appreciable  difference 
in  the  supply  of  blood  between  the  inspiratory  and  expiratory 
periods.  We  now  know  that  the  respiratory  variations  in  the 
arterial  pressure  and  in  the  frequency  of  the  contractions  of 
the  heart,  are  not  necessarily  dependent  on  the  mechanical 
effect  of  the  respiratory  movements  on  the  heart,  inasmuch  as 
they  persist  when  these  movements  are  abolished;  and  that 
they  have  their  primary  source  in  the  vasomotor  and  cardiac- 
inhibitory  centres,  which  act  rhythmically,  not  because  they 
are  subject  to  any  rhythmical  excitation,  but  because  they 
have  periods  of  waxing  and  waning  activity  which  correspond 
to  those  of  the  respiratory  centre.  A  very  little  consideration 
■hows  that  this  inference  carries  the  admission  that  the  cardiac- 
inhibitory  centre  and  the  vasomotor  centre  act  alternately,  for 
it  can  lie  seen  in  every  tracing  that  the  increase  of  arterial 
tension  determined  by  increased  vascular  tonus,  alternates 
with  the  retarded  pulse  and  diminished  tension  produced  by 
"  vagus  excitation."     In  other  words,  the  phase  of  maximum 


326  RESPIRATION. 

activity  of  the  inhibitory  centre  always  coincides  with  that  of 
minimum  activity  of  the  vasomotor  centre.  The  experiment 
by  which  it  is  proved  that  the  respiratory  phases  of  arterial 
pressure  and  pulse  frequency  are  independent  of  the  thoracic 
movement,  consists  in  curarizing  a  dog  by  the  injection  into 
the  venous  system  of  a  dose  of  curare  only  just  sufficient  to 
paralyze  the  respiratory  muscles  (5  to  10  millig.  for  a  dog  of 
10  lbs.  weight),  and  observing  graphically  the  changes  of  ar- 
terial pressure  which  occur  during  the  gradual  extinction  of 
the  respiratory  movements,  with  the  aid  of  the  apparatus  de- 
scribed above.  The  tracings,  figs.  259-261,  show  what  is  ob- 
served at  three  different  stages  of  curarization.  Curve  259 
was  drawn  when  the  animal's  muscles  were  still  active.  It 
may  be  regarded  as  normal.  Curve  2601  corresponds  to  a 
period  at  which  each  inspiration  and  expiration  is  represented 
by  a  scarcel}'  perceptible  contraction  and  dilatation  of  the 
chest.  Curve  261  to  a  still  later  condition,  in  which  the  inspi- 
ratory movements  are  indicated  by  a  mere  vibration  of  the 
lever,  produced  (as  was  observed  at  the  time)  by  momentary 
contraction  of  certain  inspiratory  muscles  which  were  not  yet 
completely  parabyzed.  We  learn  from  these  observations,  that 
during  the  gradual  extinction  of  the  respiratory  movements, 
the  intervals  between  them  correspondingly  lengthen ;  and 
that  at  first  the  variations  of  arterial  pressure  and  pulse  fre- 
quency exhibit  the  characters  which  closely  correspond  to 
those  they  exhibit  normally.  Subsequently,  the  ascents  and 
descents  of  the  mercurial  column  become  much  more  gradual, 
and  the  changes  of  frequency  less  abrupt.  Finally  they  as- 
sume, so  far  as  relates  to  arterial  tension,  the  characters  of  the 
variations  known  as  Traube's  curves,  to  be  described  in  the 
next  paragraph. 

106.  Traube's  Curves. — This  term  is  applied  by  physio- 
logists to  the  rhythmical  variations  of  arterial  pressure  which 
occur  in  curarized  animals,  after  complete  cessation  of  the  re- 
spiratory movements,  and  section  of  both  vagi.  They  can  be 
demonstrated  in  the  rabbit,  cat,  or  dog,  but  most  readily  in 
the  last.  Traube  described  them  as  the}'  occur  in  the  absence 
of  artificial  respiration,  i.  e.,  when  the  inflations  are  for  a  time 
discontinued.  During  the  gradual  rise  of  arterial  pressure 
which,  as  we  have  already  seen,  takes  place  under  those  cir- 

1  In  fig.  260  the  notches  in  the  lower  tracing  represent  rudimentary 
inspirations  and  expirations.  The  expiratory  movements,  e  e  e,  are 
only  traceable,  however,  in  the  last  half  of  the  tracing  ;  they  follow  the 
inspiratory,  i  i  i,  at  an  interval  of  about  five  mill.  =  1£  sec.  In  fig. 
201.  the  expiratory  movements  are  wholly  indistinguishable.  All  the 
tracings  of  this  series  are  reduced  one-half  to  save  space.  The  distance 
between  the  respiratory  and  arterial  tracing  is  also  diminished  for  the 
same  reason. 


BY   DR.    BURDON-SANDERSOST.  327 

cnrastances,  the  arterial  pressure-curve  exhibits  the  undula- 
tions in  question.  It  has,  however,  been  lately  shown  by 
Hering,  that  the  state  of  asphyxia  is  far  from  being  essential, 
and  that  the  most  certain  way  of  producing  the  phenomenon 
is  to  bring  the  blood  of  the  animal  into  a  state  which  corre- 
sponds to  dyspnoea,  not  b}r  stopping  the  artificial  respiration 
altogether,  but  by  gradually  diminishing  the  quantity  injected 
at  each  stroke.  In  the  arterial  tracings  so  obtained  it  is  seen 
that  the  cardiac  intervals  are  of  uniform  duration — in  other 
words,  that  there  are  no  variations  of  pulse-frequency,  the  vagi 
having  been  divided.  When  these  nerves  are  left  intact,  curves 
are  obtained  (fig.  2621)  in  which  the  variations  of  the  pulse 
intervals  exhibit  the  same  relation  to  those  of  the  arterial 
tension  as  in  the  normal  condition — the  pulse-frequency  being 
greater  in  the  ascending  limb  of  each  respiratory  wave  than 
in  the  descending.  From  this  we  learn  that  the  variations  of 
frequency  are  dependent  on  the  integrity  of  the  vagi.  The 
proof  that  the  variations  of  pressure  are  vascular  in  their 
origin,  and  depend  on  corresponding  changes  of  arterial  tonus, 
is  shown  by  two  experimental  results,  viz. :  (a)  that  although 
after  section  of  the  spinal  cord,  arterial  pressure  is  still  sub- 
ject to  variations  which  are  no  doubt  dependent  on  changes 
of  arterial  tonus,  these  are  very  irregular ;  and  (6)  that  the 
rhythmical  variations  of  pressure  persist  after  the  influence  of 
the  heart  has  been  eliminated.  The  latter  fact  has  been  de- 
monstrated b)r  Hering,  who  has  shown  that  if  circulation  is 
maintained  artificially,  independently  of  the  heart,  in  an  ani- 
mal which  is  placed  in  other  respects  in  conditions  favorable 
to  the  production  of  "  Traube's  curves,"  they  exhibit  them- 
selves with  the  same  distinctness  as  when  the  heart  is  in  action. 
The  conclusion  to  be  derived  from  the  preceding  experiments 
may  be  expressed  as  follows:  The  rhythmical  variations  of 
arterial  pressure  which  are  associated  with  the  respiratory 
movements,  are  dependent  on  corresponding  variations  of 
arterial  tonus,  but  the  variations  of  the  frequency  of  the  con- 
traction of  th£  heart  are  governed  by  the  inhibitor}'  nervous 
sj-stem  of  that  organ.  In  accepting  this  proposition,  it  must 
not  be  forgotten  that  under  normal  conditions  the  thoracic 

1  The  tracings,  fig.  2G2,  are  those  of  a  curarized  dog  with  undivided 
vagi,  in  which  air  is  injected  into  the  lungs  at  regular  intervals,  but  in 
insufficient  quantity.  The  arterial  curve  differs  from  "Taube's"  only 
in  this  respect — that  in  the  ascending  limb  of  each  wave,  the  wavelets 
which  express  the  arterial  pulsations  are  more  frequent  than  in  the 
descending.  In  the  lower  tracing  the  ascents  mark  the  strokes  of  the 
artificial  respiration  apparatus,  which  was  working  at  intervals  of  five 
seconds  ;  the  variations  of  arterial  pressure  shown  in  the  upper  tracing 
follow  the  rhythm  of  the  natural  respiratory  movements,  and  conse- 
quently do  not  correspond  with  the  inflations. 


328  RESPIRATION. 

movements  co-operate  in  the  most  powerful  manner  in  the  pro- 
duction of  the  result;  for  in  every  inspiration,  so  long  as  the 
pleural  cavities  remain  closed,  the  diastolic  impletion  of  the 
heart  is  favored  by  the  filling  of  the  venie  cavae,  and  thereby 
the  vigor  of  the  succeeding  contractions  of  the  heart  is  in- 
creased. This  is  particularly  the  case  in  animals  which  (like 
the  dog  and  cat)  breathe  thoracically. 

Section  VII. — Apncea,  Dyspncea,  and  Asphyxia. 

The  terms  apncea,  dyspnoea,  and  asphyxia,  are  applied  in 
physiology  to  the  states  of  functional  disorder  which  are 
produced  by  excess  and  defect  of  oxygen  in  the  blood,  the 
differences  between  them  being — in  accordance  with  a  gene- 
ralization so  well  established  that  it  may  be  regarded  as  a  law 
— that  the  activity  of  the  respiratory  movements  varies  in- 
versely as  their  effect  on  the  blood. 

107.  Apncea. — When  the  blood  is  saturated  with  ox3rgen, 
respiratory  movements  cease,  and  the  animal  is  said  to  be  in  a 
state  of  apncea.  The  fact  can  be  demonstrated  with  great 
ease  in  the  rabbit  by  the  ordinary  method  of  artificial  respira- 
tion. If  the  intervals  between  the  inflations  of  the  lungs 
are  gradually  shortened,  the  inspiratory  movements  become 
shallower  and  shallower,  and  finally  cease.  The  heart  con- 
tinues to  beat  vigorously  and  somewhat  more  frecpaently  than 
before.  The  visible  mucous  membranes  present  a  perfectly 
natural  appearance.  The  eye  closes  instantly  when  the  con- 
junctiva is  touched,  and  the  state  of  the  pupil  is  normal.  In 
short,  all  the  functions  excepting  the  respiratory  movements 
go  on  as  before.1 

108.  Dyspncea. — We  have  already  studied  the  phenomena 
of  dj'spncea  so  far  as  relates  to  the  muscular  movements.  We 
have  seen  that  in  the  rabbit,  when  the  access  of  air  to  the  cir- 
culating blood  is  gradually  diminished,  other  muscles  begin  to 
co-operate  wdth  the  diaphragm  in  the  inspiratory  act,  in  an 
order  which,  as  a  rule,  is  a  follows:  Inter costale$  externi,  leva- 
tores  costarum  breves, intercartilaginei, scaleni,  serrati  jyostici. 
As  external  signs  of  dyspncea,  the  drawing  down  of  the  larynx 
in  inspiration  by  the  muscles  which  cover  the  trachea,  and  the 
expansion  of  the  upper  part  of  the  chest  by  the  intercartilagi- 

1  The  fact  of  apncea  was  first  demonstrated  by  Hook,  before  the 
Royal  Society  in  October,  16G7.  His  experiment  consists  in  opening 
the  chest  of  a  dog,  distending  the  lungs  witli  bellows,  and  keeping  up 
a  constant  stream  of  air  through  the  organ  through  punctures  made  in 
its  surface  for  the  purpose.  He  found  that,  although  "the  eyes  were 
all  the  time  very  quick,  and  the  heart  beating  regularly,"  there  were 
no  respiratory  movements.  The  term  "apncea"  was  first  applied  to 
this  condition  by  Rosenthal,  in  1864. 


BY   DR.    BURDON-SANDERSON.  329 

nous  muscles  and  external  intercostals,  are  the  most  important, 
as  indicating  successive  stages.  For  a  comprehensive  study 
of  dyspnoea,  as  it  affects  not  merely  the  respiratory  movements, 
but  the  circulation  and  the  functions  of  the  nervous  system, 
those  experiments  are  best  in  which  the  disorder  can  be  watched 
from  its  beginnings  in  mere  increase  of  functional  activity  (hy- 
perpncea),  to  its  issue  in  asphyxia  or  suffocation.  These  may 
consist,  either  in  complete  obstruction  of  the  air-passages,  in 
which  case  death  occurs  very  rapidly  (in  4-5  minutes  in  the 
dog,  a  shorter  time  in  the  rabbit),  in  allowing  the  animal  to 
breathe  out  of  a  bag  with  which  its  respiratory  cavitj-  is  in 
air-tight  communication,  or  from  a  gasometer  (the  instrument 
represented  in  Fig.  251),  into  which  definite  mixtures  of  gases 
can  be  continuously  introduced. 

109.  Asphyxia  by  Complete  Occlusion  of  the  Tra- 
chea.— For  this  purpose,  a  canula  must  be  fixed  air-tight  in 
the  trachea,  the  mouth  of  which  is  of  such  form  that  it  can  be 
plugged  with  a  cork.  If  it  is  desired  to  obtain  a  tracing  of  the 
variations  of  tension  which  the  air  so  inclosed  in  the  respira- 
tory cavity  undergoes,  the  cork  must  be  perforated  and  fitted 
with  a  tube  which  communicates  with  a  mercurial  manometer, 
the  movements  of  which  are  recorded  on  the  cylinder  of  the 
kymograph,  simultaneously  with  the  variations  of  pressure 
in  the  crural  artery.  The  tube  must  be  of  small  bore  and  have 
thick  walls.  The  phenomena,  as  they  present  themselves  in 
the  dog,  may  be  enumerated  as  follows:  First  minute. — Ex- 
cessive respiratory  movements,  in  which  at  first  the  expansive 
efforts  of  the  thoracic  muscles,  afterwards  the  expulsive  efforts 
of  the  muscles  of  the  abdominal  wall,  are  most  violent.  During 
this  period  the  arterial  pressure  increases,  but  it  is  extremely 
difficult  to  measure  it,  on  account  of  the  modifying  influence 
of  the  thoracic  movements.  Towards  the  close  of  the  first 
minute  the  animal  becomes  convulsed.  These  convulsions  must 
be  attentively  studied,  because  they  are  the  type,  by  compari- 
son with  which  all  other  convulsions  of  the  same  order  are  de- 
scribed or  defined.  The  prominent  fact  with  respect  to  these 
convulsions  is  that  they  are  expiratory.  At  first,  indeed,  they 
seem  to  be  nothing  more  than  exaggerations  of  the  previous 
expulsive  efforts.  Afterwards,  the  contractions  of  the  proper 
expiratory  muscles  are  accompanied  by  more  or  less  irregular 
spasms  of  the  muscles  of  the  limbs,  particularly  of  the  flexors. 
Second  minute. — Early  in  the  second  minute  the  convulsions 
cease,  often  suddenly;  simultaneously  with  their  cessation,  the 
expiratory  efforts  become  indistinguishable.  The  iris  is  now 
dilated  to  a  rim  ;  the  eye  does  not  close  when  the  corneals 
touched,  nor  does  the  pupil  react  to  light ;  all  reflex  reaction 
to  stimuli  has  ceased.  All  the  muscles,  except  those  of  inspi- 
ration, are  flaccid,  and  the  animal  lies  in  a  state  of  tranquil- 


830  RESPIRATION. 

lity,  which  contrasts  in  the  most  striking  way  with  the  storm 
which  preceded  it.  The  condition  of  the  circulation  at  this 
stage  can  be  best  judged  of  by  the  tracing,  Fig.  2036. '  Inspi- 
rations occur  at  long  but  tolerably  regular  intervals,  and  eacli 
inspiratory  act  is  accompanied,  not,  as  in  normal  inspiration, 
by  an  increase  of  arterial  pressure,  but  by  a  marked  diminu- 
tion. The  mean  arterial  pressure,  which  at  the  beginning  of 
the  second  minute  is  far  above  the  normal,  sinks  considerably 
below  it  towards  the  end.  Third  and  fourth  minutes. — As 
death  approaches,  the  thoracic  and  abdominal  movements, 
which  are  entirely  inspirator}',  become  slower  and  slower  as 
well  as  shallower.  The  diminution  of  frequenc}'  is,  however, 
never  uniform,  the  inspirations  occurring,  for  the  most  part, 
in  successions  of  two  or  three  efforts,  with  long  pauses  between 
them.  In  each  act  the  accessory  muscles  of  inspiration  co- 
operate with  the  diaphragm  in  the  production  of  the  result, 
and  towards  the  close  other  muscles  come  into  spasmodic 
action  which  are  not  usually  regarded  as  inspiratory  muscles 
at  all,  although,  in  all  probability,  they  act  by  virtue  of  motor 
impulses  originating  in  the  inspiratory  centre.  In  these 
spasms,  which  accompany  the  final  gasps  of  an  asphyxiated 
animal,  the  head  is  thrown  back,  the  trunk  straightened  or 
arched  backwards,  and  the  limbs  are  extended,  while  the  mouth 
gapes  and  the  nostrils  dilate.  They  are  called  by  pli3rsiologists 
stretching  convulsions,  and  must  be  carefully  distinguished 
by  the  student  from  the  expiratory  convulsions  previously 
described. 

110.  Asphyxia  by  Slow  Suffocation. — When  an  animal 
is  allowed  to  breathe  the  same  quantity  of  air  repeatedly 
and  continuously  out  of  a  bag,  the  process  being  of  much 
longer  duration,  the  phenomena  can  be  studied  with  greater 
facility.  As,  however,  its  duration  depends  on  two  variable 
conditions,  viz.,  the  respiratory  capacity  of  the  animal  and  the 
capacity  of  the  receptacle  from  which  it  breathes,  it  is  not  pos- 
sible to  describe  the  phenomena  with  reference  to  periods  of 
fixed  duration.  It  is  sufficient  to  divide  the  process  into  two 
stages,  the  limits  of  which  will  be  readily  understood  from  the 
preceding  paragraph.  The  first  may  be  called  that  of  hyper- 
pnoea.  The  respiratory  movements,  at  first  natural,  are  gradu- 
ally exaggerated,  both  as  regards  their  extent  and  frequency, 
while  the  arterial  pressure  rises.  Towards  the  end  of  the 
period,  as  in  the  former  case,  the  expiratory  movements  gain 
in  vigor,  both  absolutely  and  relatively  to  those  of  inspiration, 
so  that  each  inspiratory  act  is  immediately  followed  by  a  sud- 

1  Fig.  2636  is  taken  toward  the  end  of  the  second  minute  of  asphyxia 
by  occlusion.  The  mean  arterial  pressure  is  gradually  sinking;  each  in- 
spiration is  accompanied  by  a  depression  of  arterial  pressure. 


BY   DR.    BURDON-SANDERSON.  331 

den  tightening  of  the  anterior  abdominal  wall,  accompanied  by 
convulsive  twitchings  of  the  limbs.  The  second  stage  begins 
by  a  change  in  the  phenomena  quite  as  marked  as  when  the 
exclusion  of  air  is  complete.  Suddenly,  the  violent  expulsive 
efforts  cease,  and  the  inspiratory  movements  assume  the  charac- 
ter already  described,  consisting  in  spasmodic  contractions  of 
the  diaphragm,  accompanied  by  gasping  movements  of  the 
head  and  neck,  the  most  marked  difference  being  that  the  arte- 
rial pressure,  instead  of  sinking  with  each  inspiratory  effort, 
rises,  the  rise  being  accompanied  by  an  equally  considerable 
acceleration  (see  Fig.  263a1).  In  the  dog  this  phenomenon  is  so 
obvious  that  it  can  be  judged  of  quite  as  well  by  watching  the 
mercurial  column  of  the  manometer  as  by  the  tracing.  As  re- 
gards the  gradual  diminution  of  the  frequency  of  the  contrac- 
tions of  the  heart  during  the  first  part  of  the  period  of  collapse, 
and  their  gradual  acceleration  as  extinction  approaches,  the 
phenomena  are  the  same  whatever  be  the  mode  in  which 
asphyxia  is  produced.  As  regards  the  final  respiratory  move- 
ments, and  the  stretching  convulsions  which  are  associated 
with  them,  nothing  need  be  added  to  the  description  previously 
given. 

The  preceding  facts  may  be  summed  up  as  follows:  In  the 
first  stage  of  asphyxia  (understanding  by  the  term,  that  part 
of  the  process  which  culminates  in  the  struggle),  the  phenomena 
are  of  two  kinds.  At  first,  we  have  merely  over-activity  of  the 
respiratory  apparatus  (hyperpncea) ;  at  the  end,  expiratory 
convulsion.  The  convulsive  movements  are  so  distinct  from 
those  proper  to  expiration,  that  we  are  compelled  to  assign 
their  origin  to  a  special  centre.  This  centre  is  often  called  the 
''convulsion  centre."  It  is  probably  identical  with  that  from 
which  the  co-ordinated  expiratory  movements  of  dyspnoea  (hy- 
perpncea) spring;  for  in  asphyxia  we  see  that  these  last  pass 
into  convulsions  by  insensible  gradations.3  When  the  struggle 
with  which  the  first  stage  closes  is  succeeded  by  the  calm  of 
the  second,  all  voluntary  muscles,  excepting  those  which  are 

1  Fig.  2G3«  is  taken  at  the  beginning  of  the  second  stage  of  slow 
asphyxia.  Almost  every  inspiration  is  immediately  followed  by  two  or 
three  cardiac  contractions,  succeeding  each  other  at  very  short  in- 
tervals. 

2  It  is  important  to  notice  that  the  convulsion  of  asphyxia  is  identical 
with  that  produced  in  Kussmaul  and  Tenner's  experiment,  both  having 
the  expiratory  character.  If  that  experiment  is  performed  in  an  animal 
in  the  state  of  apncea,  the  arrest  of  the  arterial  circulation  in  the  intra- 
cranial nervous  centres  at  once  induces  respiratory  movements;  and  if 
the  closure  of  the  arteries  continues,  the  animal  passes  through  the  suc- 
cessive stages  of  dyspnrea,  and  finally  becomes  convulsed  just  as  in  as- 
phyxia. If  at  this  point  the  arteries  are  released,  the  animal  relapses 
gradually,  after  one  or  two  vigorous  inspirations,  into  the  condition  of 
apncea. 


332      ,  RESPIRATION. 

either  inspiratory  or  associated  in  their  action  with  inspiration, 
become  relaxed.  The  inspiratory  muscles,  on  the  contrary,  act 
with  great  vigor. 

111.  State  of  the  Circulation  in  Asphyxia. — This  may 
be  best  studied  by  actually  observing  the  condition  of  the  heart 
and  great  vessels  in  a  narcotized  animal,  of  which  the  chest  has 
been  opened  while  respiration  is  maintained  artificially.  In  a 
perfectly  chloralized  animal,  the  heart  may  be  exposed  very 
rapidly,  as  follows:  The  integument  covering  the  left  side  of 
the  chest  having  been  turned  hack,  a  series  of  strong  ligatures 
are  passed  round  the  costal  cartilages,  close  to  the  left  edge  of 
the  sternum,  in  such  a  way  that  each  ligature  enters  the  thoracic 
cavity  by  one  intercostal  space  and  passes  out  by  the  next;  a 
second  set  of  ligatures  are  passed  in  a  similar  manner  round  the 
ribs  in  a  vertical  line  outside  of  the  prsecordia.  The  ligatures 
having  been  tightened,  the  quadrangular  space  between  them 
can  be  cut  away  without  any  bleeding.  The  pericardium  having 
then  been  opened,  the  thoracic  organs  can  be  perfectly  well  seen. 
If  now  after  continuing  the  artificial  respiration  till  apnoea  is 
produced,  it  is  suspended,  all  the  degrees  of  respiratory  activity, 
viz.,  apncea,  natural  breathing,  hyperpnoea,  dyspnoea,  convul- 
sion, asphyxia,  will  be  witnessed  in  the  order  in  which  they  have 
been  mentioned,  and  it  will  be  seen  that  no  very  obvious  change 
in  the  condition  of  the  heart  and  great  vessels  will  occur  until 
the  last  stage  (corresponding  to  what  I  have  called  the  second 
stage  of  asphyxia)  is  approached.  During  the  convulsive  strug- 
gle, and  particularly  towards  its  close,  the  heart  enlarges  to 
something  like  the  double  of  its  former  dimension,  this  enlarge- 
ment being  due  (as  the  attentive  observer  will  have  no  difficult}' 
in  satisfying  himself)  to  the  lengthening  of  the  diastolic  inter- 
val and  to  the  quantity  of  blood  contained  in  the  great  veins, 
which  in  fact  are  so  distended,  that  if  cut  into  they  spirt  like 
arteries.  If  at  this  point  air  is  again  injected,  the  heart  begins 
after  a  few  seconds  to  contract  more  rapidly,  and  in  a  moment 
or  two,  emptying  itself  of  its  overcharge  of  blood,  resumes  its 
former  size.  The  effect  of  these  changes  on  the  arterial  pres- 
sure can  be  best  studied  in  a  curarized  animal,  of  which  the 
crural  or  carotid  has  been  connected  with  the  kymograph.  If, 
in  such  an  animal,  artificial  respiration  is  discontinued  till  the 
arterial  pressure,  after  first  increasing,  sinks  as  low  as  20  to  40 
millimetres,  the  tracing  shows  that  the  diastolic  intervals  are 
much  lengthened.  If  then  air  is  injected,  the  arterial  pressure 
after  an  interval  of  5  or  6  seconds  suddenly  rises,  while  the 
curve  expressing  the  rise  indicates  the  extreme  frequency  of 
the  contractions  by  which  the  heart  empties  itself  of  its  con- 
tents, or  rather  pumps  on  the  blood  contained  in  the  over-full 
veins  to  the  arterial  system.  (See  fig.  2G4,  in  which  i  indicates 
the  moment  of  injection  of  air.)     During  this  effort,  the  mer- 


BY   DR.    BURDON-SANDERSON.  333 

curial  column  usually  rises  above  the  normal,  but  after  it  is 
over,  subsides  to  a  height  which  is  nearly  the  same  as  that 
about  which  it  oscillated  before  artificial  respiration  was  sus- 
pended. The  explanation  of  these  phenemena  may  be  given  in 
a  few  words.  One  of  the  effects  of  diminishing  the  proportion 
of  oxygen  in  the  circulating  blood  is  to  excite  the  vasomotor 
centre,  and  thus  determine  general  contraction  of  the  small 
arteries.  The  immediate  consequence  of  this  contraction  is  to 
fill  the  venous  S3rstem,  in  the  production  of  which  result  the 
contraction  of  the  expiratory  muscles  of  the  trunk  and  extremi- 
ties powerfully  co-operates.  The  heart  being  abundantly  sup- 
plied with  blood,  fills  rapidly  during  diastole  and  contracts 
vigorously,  in  consequence  of  which  and  of  the  increased  resist- 
ance in  front,  the  arterial  pressure  rises.  This  last  effect  is 
however  temporary ;  the  diastolic  intervals  being  lengthened 
by  the  excitation  of  the  inhibitory  nervous  system,  and  the 
heart  itself  weakened  by  defect  of  oxygen,  the  organ  soon 
passes  into  the  state  of  diastolic  relaxation  already  described. 
Its  contractions  become  more  and  more  ineffectual  till  they 
finall}'  cease,  leaving  the  arteries  empty,  the  veins  distended, 
its  own  cavities  relaxed  and  full  of  blood.  That  the  small  arte- 
ries are  contracted  in  asphyxia  we  learn  by  inspecting  them 
(see  §  49).  The  narrowing  is  as  marked  as  it  is  during  elec- 
trical excitation  of  the  medulla  oblongata.  In  both  cases  the 
contraction  induces  increased  arterial  pressure,  but  there  is 
this  difference,  that  whereas  in  the  latter  case  the  heart  is  not 
interfered  with,  in  the  former  its  functional  activity  is  much  im- 
paired by  the  condition  of  the  blood.  Consequently,  the  rise 
of  the  arterial  pressure  is  much  greater  in  proportion  to  the 
degree  of  contraction  of  the  arteries  during  excitation  of  the 
medulla  than  in  asphyxia. 

112.  Examination  of  the  Heart  after  Death  by- 
Asphyxia. — If  the  heart  is  rapidly  exposed  immediately 
after  death  by  asphyxia,  and  a  strong  ligature  tightened  round 
the  roots  of  the  great  vessels,  the  organ  may  be  readily  cut 
out  without  allowing  any  blood  to  escape  from  its  cavities. 
The  quantity  of  blood  contained  in  the  right  and  left  side  re- 
spectively may  be  measured  by  carefully  opening  the  ventri- 
cles and  allowing  their  contents  to  flow  into  separate  measure 
glasses.  It  is  always  found  that  all  the  cavities  of  the  heart 
are  filled  to  distension,  the  quantities  in  the  right  and  left 
cavities  respectively,  usually  being  to  each  other  about  in  the 
proportion  of  2  to  3.  The  lungs  are  always  pale;  if,  however, 
the  body  is  kept  for  a  few  hours,  those  parts  of  the  organs 
which  are  lowest  becomes  airless  and  soaked  with  sanguino- 
lent  liquid. 

113.  Demonstration  of  the  Chemical  Changes  -which 
occur  in  the  Blood  in  Dyspnoea  and  Asphyxia. — It 


334  RESPIRATION. 

being  known  that  in  suffocation  two  changes  take  place  in  the 
chemical  condition  of  the  blood — diminution  of  oxygen  and 
increase  of  carbonic  acid  gas — it  is  obviously  not  unreasonable 
to  attribute  the  phenomena  either  to  the  one  or  the  other  of 
these  changes,  or  to  the  combination  of  both.  In  the  preced- 
ing pages  it  has  been  assumed  that  the}'  are  due  to  the  dimi- 
nution of  oxygen.  The  chief  proofs  that  this  is  so  are  as  fol- 
lows:  In  order  to  demonstrate  in  a  striking  way  and  in  one 
experiment  that  diminution  of  ox}-gen  in  the  air  breathed 
does,  and  that  excess  of  carbonic  acid  gas  does  not,  produce 
the  phenomena  of  dj'spncea,  the  following  method,  devised  by 
Rosenthal,  may  be  employed.  The  mercurial  gosometer  (fig. 
251)  is  filled  with  oxj-gen.  The  animal  is  then  allowed  to 
breathe  the  gas  in  the  way  described  (§  95)  until  it  ma}'  be 
reasonably  supposed  that  the  air  contained  in  the  air-passages 
is  displaced  by  it.  This  occurs  in  the  rabbit  in  about  ten 
respirations.  The  communication  is  then  opened  between  the 
valve  B  and  the  receiver,  while  the  exit  tube  is  clipped  so  that 
the  animal  both  inspires  from  the  gasometer  and  expires  into 
it.  As  the  experiment  goes  on,  it  is  obvious  that  the  propor- 
tion of  carbonic  acid  increases  and  must  continue  to  increase, 
until  that  gas  attains  such  a  tension  in  the  gasometer  that  no 
further  escape  from  the  blood  is  possible.  At  first  the  volume 
of  gas  in  the  gasometer  undergoes  no  sensible  diminution, 
for  the  animal  expires  nearly  as  much  of  carbonic  acid  as  it 
inspires  of  oxygen  ;  afterwards,  as  the  quantity  of  carbonic 
acid  gas  given  off  becomes  less  and  less,  the  cylinder  sinks  in 
each  inspiration  more  and  more.  As  soon  as  this  is  the  case 
it  is  of  course  absolutely  certain  that  the  animal  is  breathing 
an  atmosphere  containing  a  large  excess  of  carbonic  acid  gas, 
yet  notwithstanding,  there  is  no  sign  of  asphyxia,  the  reason 
being  that  the  oxygen  still  exists  in  the  mixture  in  a  propor- 
tion exceeding  that  in  which  it  exists  in  the  atmosphere,  or  at 
all  events,  not  falling  far  short  of  it.  When  at  a  still  later 
period  the  breathing  begins  to  be  excessive,  the  dyspnoea  can 
at  first  be  relieved  by  increasing  the  pressure  to  which  the 
gases  contained  in  the  gasometer  are  exposed.  This,  of  course, 
while  it  favors  the  absorption  of  oxygen,  equally  favors  that  of 
carbonic  acid  gas ;  that  the  latter  has  no  physiological  effect 
cannot  be  maintained,  but  the  experiment  proves  that  its 
effect  is  very  inconsiderable. 

The  direct  proof  that  dyspnoea  is  dependent  on  defect  of 
oxygen,  is  obtained  by  the  analysis  of  the  gases  of  the  blood 
in  an  animal  which  has  been  asphyxiated  by  the  inhalation  of 
pure  nitrogen.  Pfluger  has  found  that  an  animal  (dog)  breath- 
ing nitrogen  becomes  hyperpnoeic  in  15  seconds.  In  20  seconds 
the  struggle  is  at  its  height,  the  blood  being  already  very  dark. 
In  Pfluger's  experiments,  blood  was  allowed  to  flow  from  an 


BY    DR.    BURDON-SANDERSON.  335 

artery  into  a  recipient  for  the  analysis  of  its  gases,  at  from  half 
a  minute  to  a  minute  after  the  beginning  of  the  inhalation  of 
nitrogen,  the  animal  being  already  in  the  second  stage  of  as- 
phyxia. It  was  found,  for  example,'  that  the  blood  of  an  animal 
which  before  breathing  nitrogen  contained  18.8  per  cent,  per 
vol.  of  ox}rgen  (at  760  millim.  and  0°  C),  contained  after  breath- 
ing nitrogen  for  one  minute  a  mere  trace  of  oxygen  (0.3  per 
cent.) ;  during  the  same  period  the  carbonic  acid  gas  had  dimin- 
ished from  47.2  per  cent,  to  39.4  per  cent.  These  experiments 
are  referred  to  here  on  account  of  their  fundamental  importance. 
The}^  are  much  too  difficult  for  repetition. 

114.  Demonstration  that  the  Pulmonary  Termina- 
tions of  the  Vagus  Nerves  are  Excited  by  Distension 
of  the  Lungs. — It  was  long  ago  surmised  by  physiologists 
(particularly  by  Rosenthal)  that  the  pulmonary  branches  of 
the  vagus  nerves  contain  afferent  fibres,  which  are  excited  by 
the  expansion  of  that  organ,  and  that  these  fibres  take  part  in 
the  regulation  both  of  the  movements  of  the  heart  and  those  of 
respiration.  The  proof  of  this  has  been  lately  given  by  Hering. 
A  dog  having  been  narcotized  with  morphia  or  opium,  one  arm 
of  a  T-shaped  canula  is  secured  in  the  trachea,  the  other  being- 
connected  with  a  mercurial  manometer.  To  the  stem  an  India- 
rubber  connector  is  fitted,  which  is  guarded  by  a  screw  clip, 
and  ends  in  a  blowing  tube:  a  canula  is  placed  in  the  carotid 
and  connected  with  the  kymograph.  These  preparations  having 
been  made,  an  observation  of  arterial  pressure  is  taken.  The 
clockwork  being  still  in  motion,  the  experimenter  distends  the 
lungs  of  the  animal  until  the  distal  column  of  the  manometer 
stands  about  30  or  40  millimetres  above  the  other,  and  then 
closes  the  clip.  Two  important  results  are  produced.  In  the 
first  place,  the  inspiratory  muscles  are  thrown  out  of  action, 
and  remain  relaxed  so  long  as  the  distension  lasts,  while  those 
of  expiration  are  brought  into  continuous  and  energetic  con- 
traction ;  and  secondly,  the  frequency  of  the  contractions  of 
the  heart  is  more  than  doubled.  In  the  preceding  experiment 
the  circulation  is  considerably  affected  by  the  increased  pres- 
sure exercised  by  the  distended  lungs  on  the  heart  and  great 
veins  ;  consequently,  the  increased  frequency  of  the  pulse  might 
be  attributed  in  whole  or  in  part  to  this  circumstance  rather 
than  to  the  pulmonary  distension.  To  meet  this  objection,  the 
experiment  may  be  modified  as  follows:  A  dog  is  narcotized 
and  respiration  maintained  artificially,  the  apparatus  being  so 
arranged  that  at  any  moment  the  lungs  may  be  distended  as 
in  the  last  case.  This  done,  the  thoracic  organs  are  completely 
exposed  by  removing  the  anterior  wall  of  the  chest  in  the  man- 
ner described  in  §  49  :  it  is  then  seen  that  the  effect  of  inflation 

1  Pfliiger's  Archiv.,  vol.  I.  p.  94. 


336  ANIMAL    HEAT. 

on  the  heart  is  just  the  same  as  when  the  thorax  is  closed. 
These  results  are  sufficient  to  show  the  pulmonary  distension 
and  acceleration  of  the  contraction  of  the  heart,  stand  in  the 
relation  to  each  other  of  cause  to  effect.  That  the  influence  of 
the  former  on  the  latter  is  exercised  through  the  nervous  sys- 
tem, and  consequently  through  the  vagi  (these  being  the  only 
known  channel  by  which  the  lungs  are  in  communication  with 
the  nervous  centres)  is  sufficiently  obvious.  Accordingly,  we 
should  expect  that  if  this  channel  were  interrupted  the  effect 
would  be  annulled,  and  experiment  proves  that  it  is  so.  The 
demonstration  is,  however,  very  difficult,  for  in  the  dog  the 
pulsations  of  the  heart  are  already  so  rapid  after  section  of  the 
vagi  that  no  further  acceleration  is  possible  ;  a  negative  result, 
therefore,  would  mean  nothing.  Hering  has  met  this  difficulty 
by  carefully  exciting  the  peripheral  end  of  one  of  the  divided 
nerves  after  section  of  both  (using  Ilelraholtz's  modification), 
so  as  to  reduce  the  frequency  of  the  heart's  action,  and  repeat- 
ing the  pulmonary  distension  under  these  altered  conditions  ; 
the  result  was  still  negative.  These  experiments  teach  us  two 
important  facts  relating  to  the  innervation  of  the  lungs,  viz., 
that  the  pulmonary  branches  of  the  vagus  contain  afferent 
fibres,  the  excitation  of  which  by  pulmonary  distension  tends 
to  weaken  or  paralyze  both  the  inspiratory  and  cardiac  centres 
in  the  medulla  oblongata ;  the  one  action  showing  itself  in  the 
complete  cessation  of  the  rhythmical  efforts  of  the  inspiratory 
muscles,  the  other  in  the  shortening  of  the  diastolic  intervals 
of  the  heart.  The  subject  requires  much  fuller  investigation 
than  it  has  yet  received. 


CHAPTER  XVIII. 

ANIMAL  HEAT. 

The  temperature  of  the  body  is  dependent  on  the  relative 
activit}T  of  two  sets  of  processes,  viz. :  those  by  which  heat  is 
produced  or  generated,  and  those  by  which  it  is  destroyed  or 
lost.  The  subject  admits  of  being  correspondingly  divided 
into  two  parts — the  study  of  the  processes,  and  the  stud}'  of 
the  resulting  state.  The  former  is  based  on  the  measurement 
of  the  quantity  of  heat  set  free  at  the  surface  during  a  given 
period  (Calorimetry) ;  the  second  on  the  measurement  of  the 
temperature  existing  in  the  circulating  blood  and  the  tissues 
at  the  moment  of  observation  (Thermometry). 


BY   DR.    BURDON-SANDERSON.  337 


Section  I. — Calorimetry. 


The  production  of  heat  is  one  of  the  essential  functions,  of 
living  tissue ;  consequently,  wherever  there  are  living  cells, 
heat  is  generated  at  all  times.  We  assume,  at  the  outset,  that 
the  source  of  production  is  the  sum  of  the  chemical  processes 
which  take  place  in  the  body ;  and  that  under  all  circum- 
stances, so  long  as  the  tissues  are  neither  growing  nor  wasting, 
the  quantity  of  heat  produced  by  the  oxidation  of  the  food 
consumed  is  equal  to  the  quantity  which  would  have  been 
produced  had  the  same  quantity  of  oxidizable  substance  been 
converted  into  similar  more  or  less  oxidized  products  out  of 
the  bod}7. 

115.  There  are  two  distinct  methods  by  which  a  theoretically 
complete  determination  of  the  quantity  of  heat  products  in 
the  body  in  a  given  time  can  be  arrived  at.  The  first  consists 
in  deducting  the  heat-producing  power  (heat  value)  of  the 
substances  discharged  from  the  body  in  a  given  time,  from  the 
heat  value  of  the  substances  consumed.  The  second  is  based 
on  the  actual  measurement  of  the  quantity  of  heat  discharged 
in  a  given  time.  In  the  former  case  the  difference  obtained 
expresses  the  amount  of  heat  produced  in  the  period,  'provided 
that  the  animal  is  in  a  state  of  nutritive  equilibrium — i.  e., 
that  its  tissues  are  neither  growing  nor  wasting.  In  the  latter, 
the  measurement  gives  the  desired  result,  provided  that  the 
discharge  is  exactly  equal  to  the  production  of  heat — i.  e.,  that 
the  temperature  of  the  body  remains  the  same. 

With  reference  to  the  first  method,  as  it  reposes  entirely  on 
chemical  and  .physical  operations,  some  of  which  do  not  fall 
within  the  scope  of  this  work,  while  others  will  be  described 
under  other  heads,  all  that  is  necessary  is  to  make  clear  the 
principles  of  its  application.  So  long  as  an  animal  is  in 
nutritive  equilibrium  (see  above)  the  combustible  material 
actually  consumed,  i.  <?.,  oxidized  in  its  body  in  a  given  time, 
may  be  known  by  deducting,  from  the  quantity  of  such 
material  actually  swallowed,  the  quantity  discharged  in  the 
fieces.  This  determination  is,  therefore,  purely  a  question  of 
chemical  analysis. 

The  heat-producing  powers  of  the  chief  constituents  of  food 
have  been  determined  approximative^  by  Frankland,  who 
finds,  for  example,  that  one  gramme  of  albumin;  in  under- 
going complete  combustion  into  water,  carbonic  acid,  and 
ammonia,  produces  heat  enough  to  raise  4998  grammes  of 
water  one  degree  centigrade.  This  fact  we  express  by  stating 
that  4998  is  the  heat  value  of  albumen.  In  like  manner 
Frankland  has  found  the  heat  value  of  lean  beef  to  be  5103, 
and  of  the  fat  9069.  If,  therefore,  it  were  possible  to 
determine  how  much  of  any  of  these  substances  is  consumed, 
22 


338  ANIMAL    HEAT. 

say  per  diem,  it  is  clear  that  we  could  readily  calculate  how 
much  heat  would  be  produced,  provided  that  the  consumption, 
i,  e.,  oxidation,  were  complete.  As  regards  the  albuminous 
elements  of  food,  no  such  complete  oxidation  takes  place,  for 
the  elements  of  these  compounds  do  not  leave  the  organism  in 
the  form  of  ultimate  products  of  oxidation,  but  in  great  part 
in  the  form  of  urea  and  other  imperfectly  oxidized  organic 
constituents  of  urine.  The  quantity  of  heat  actually  pro- 
duced by  a  given  weight  of  albumin,  therefore,  falls  consider- 
ably short  of  its  heat  value.  In  order  to  arrive  at  this 
quantity,  the  deduction  previous!}'  referred  to  must  be  made: 
i.  e.,  from  the  heat  value  of  the  albumin  consumed,  the  heat 
value  of  the  nitrogenous  excreted  substances  into  which  it  is 
transformed  must  be  taken:  the  difference  expresses  theoreti- 
cally the  exact  number  of  heat  units  actually  generated  by  its 
elements  in  their  passage  through  the  body.  As  regards  the 
hj'dro-carbons,  no  such  deduction  is  necessar}',  so  that  in  the 
case  of  animals  which  feed  exclusiveljr  on  these  compounds — 
e.  g.,  bees — the  quantity  of  heat  produced  is  at  once  obtained 
by  estimating  the  heat  value  of  the  food  consumed.1 

Another  chemical  method  of  estimating  the  rate  of  produc- 
tion of  heat  in  the  body  of  an  animal,  is  founded  on  the  esti- 
mation of  the  discharge  of  carbonic  acid  from  the  lungs  and 
skin.  In  carnivorous  animals  this  method  is  of  little  value, 
for,  as  we  have  seen,  so  much  of  the  food  consumed  as  consists 
of  albuminous  compounds  is  incompletely  oxidized,  so  that 
there  is  no  definite  relation  between  the  consumption  of  albu- 
minous products  and  the  amount  of  oxidation.  In  such  ani- 
mals, however,  as  can  be  fed  entirely  on  hydro-carbons  of 
known  composition,  the  carbonic  acid  gas  discharged  ma}'  be 
taken  as  an  exact  index  of  the  heat  production — not  because 
the  quantity  of  heat  produced,  as  was  at  first  erroneously  as- 
sumed, is  equal  to  the  heat  which  would  be  disengaged  by  the 
oxidation  of  the  quantity  of  carbon  actually  contained  in  the 
carbonic  acid,  and  of  the  quantity  of  hydrogen  contained  in 
the  corresponding  quantity  of  water — but  because  in  such  an 
animal  the  whole  of  the  material  consumed  is  completely  oxi- 
dized ;  so  that  the  quantity  of  carbon  discharged  as  carbonic 
acid  is  always  equal  to  the  total  quantity  of  the  same  element 
oxidized.     On  this  account  bees,  which  can  be  fed  exclusively 

1  No  results  can  be  obtained  by  this  method  unless  the  animal  is  in  a 
state  of  perfect  nutritive  equilibrium.  For  this  reason,  it  can  be  seldom 
applicable  in  the  investigation  of  physiological  or  pathological  questions 
relating  to  heat ;  for,  on  account  of  the  length  of  the  periods  over  which 
the  determinations  must  necessarily  extend,  it  gives  little  or  no  informa- 
tion as  to  the  variations  in  the  production  of  heat,  the  appreciation  of 
Which  is  practically  more  important  than  the  determination  of  the  means 
of  the  quantities  produced  per  hour  or  day. 


BY    DR.    BURDON-SANDERSON.  339 

on  hydro-carbons,  and  have  the  additional  advantage  that, 
although  they  are  of  variable  temperature,  their  heat  produc- 
tion is  as  active  as  that  of  warm-blooded  animals,  are  specially 
adapted  for  the  investigation  of  the  relation  between  heat  pro- 
duction and  oxidation. 

Under  many  circumstances  which  preclude  the  use  of  this 
method  alone,  it  is  of  value  in  combination  with  that  of  direct 
measurement,  to  be  immediately  described ;  for  the  informa- 
tion it  affords,  even  when  the  nutritive  substances  consumed 
are  parti}'  nitrogenous,  is  trustworthy.  If  the  ingestion  of 
nutritive  material  is  regular  and  uniform,  it  affords  a  rough, 
but  otherwise  reliable,  indication  of  whatever  variations  may 
occur  in  the  activity  of  the  chemical  vital  processes. 

It  will  be  readily  understood,  that  these  indications  occur 
later  than  the  causes  which  produce  them  ;  so  that  it  is  not 
until  some  time  after  any  increase  or  diminution  of  oxidation, 
that  the  corresponding  increase  or  diminution  of  the  discharge 
of  carbonic  acid  manifests  itself.  The  mode  of  gauging  the 
discharge  of  carbonic  acid  in  the  animal  bod}-  has  been  de- 
scribed in  the  previous  chapter.  In  the  application  of  the  re- 
sults of  such  determinations,  it  must  not  be  forgotten  that  the 
absolute  values  obtained  are  meaningless.  Their  use  is  limited 
to  the  interpretation  of  direct  calorimetrical  measurements. 

116.  Direct  Estimation  of  the  Quantity  of  Heat 
produced  by  an  Animal  in  a  given  Time. — The  second 
method  (to  which  alone  the  term  Calorimetry  is  strictly  appli- 
cable), consists  in  the  direct  estimation  of  the  quantity  of 
heat  (heat  units)  given  off  by  an  animal  in  a  given  time.  The 
subject  of  observation  is  placed  for  a  measured  period  in  a 
chamber,  which  is  so  constructed  that  while  it  is  continuously 
supplied  with  air  for  respiration,  it  is  surrounded  on  all  sides 
by  a  mass  of  water,  the  weight  and  temperature  of  which  are 
known.  The  construction  of  such  a  chamber  (Calorimeter) 
can  be  readily  understood  from  the  diagram,  fig.  265. 

A,  is  a  box  of  zinc  plate,  in  which  the  animal  is  placed,  the 
size  varying  according  to  the  animal  it  is  intended  to  receive. 
If  for  rabbit  or  small  dog,  it  is  15^  inches  long  by  12  inches 
wide,  and  13  inches  high.  It  possesses  two  openings,  one  of 
which  is  in  the  lid  and  communicates  with  a  large  gasometer, 
into  which  air  is  constantly  injected  by  a  Bunsen's  water  air- 
pump.  The  other  is  in  one  end,  and  opens  into  an  exit  tube 
(D;,  which  after  surrounding  the  box  twice,  terminates  in  a 
flexible  connector,  by  which  the  air  which  has  passed  through 
the  chamber  escapes.  The  section  of  this  tube,  the  purpose  of 
which  is  to  secure  the  condensation  of  the  aqueous  vapor  dis- 
charged from  the  lungs  and  skin,  is  oblong  and  rectangular; 
in  order  that  it  may  present  to  the  water  by  which  it  is  sur- 
rounded as  large  a  surface  as  possible.     The  inner  box  (A)  is 


340  ANIMAL    HEAT. 

surrounded  by  another,  which  is  of  such  dimensions  that  the 
external  surface  of  the  former  is  separated  from  the  internal 
surface  of  the  latter  by  a  space  of  an  inch  and  a  half  in  every 
direction.  This  space  contains  water  the  weight  of  which  can 
be  readily  known.  The  inner  box  can  be  fixed  into  its  place 
by  a  simple  mechanical  arrangement.  The  water-chamber  (B) 
is  contained  in  a  wooden  case  (C),  which  however  is  so  large 
that  a  considerable  space  intervenes,  which  is  closely  packed 
with  tow,  the  purpose  of  which  is  to  prevent  loss  or  gain  of 
heat  by  radiation  or  conduction,  and  thus  to  render  the  tem- 
perature of  the  interior  of  the  apparatus  entirely  independent 
of  that  of  the  surrounding  media.  For  the  same  reason  the 
external  surface  of  the  water-chamber  is  of  bright  tinplate. 
The  interior  of  the  water-chamber  is  japanned.  The  zinc  inner 
chamber  for  the  reception  of  the  animal  is  left  as  it  is. 

The  temperature  of  the  animal  having  been  measured  by 
passing  a  thermometer  an  inch  and  a  half  into  the  rectum,  it 
is  placed  in  the  box,  the  exit  tube  of  which  has  been  previously 
brought  into  communication  with  an  aspirator.  The  lid  is  then 
rapidly  but  carefully  closed  with  putty,  and  the  whole  placed 
without  loss  of  time  in  the  water-chamber.  The  water-chamber 
is  then  closed  and  immediately  covered  with  a  layer  of  tow. 
In  its  lid  there  are  two  oblong  openings  for  the  introduction 
of  stirrers.1  The  water  having  been  agitated  immediately 
after  the  introduction  of  the  box  containing  the  animal,  a 
thermometer  is  introduced  by  one  of  the  openings  already 
mentioned,  which  after  three  minutes  is  read.  The  time  having 
been  noted,  the  apparatus  is  left  to  itself  for  fifteen  minutes, 
half  an  hour,  or  an  hour,  and  the  temperature  is  again  ob- 
served after  agitation  of  the  water.  The  results  having  been 
noted,  the  animal  is  withdrawn  with  as  little  delay  as  possible 
from  the  case  containing  it,  and  the  thermometer  is  introduced 
into  the  rectum  to  the  same  distance  as  before,  and  read  after 
the  same  interval  of  time. 

In  this  way  obviously  four  readings  are  obtained — those  of 
the  animal  and  of  the  calorimeter  at  the  beginning  and  end  of 
the  given  period.  To  interpret  them  we  must  take  into  ac- 
count, not  only  the  relative  weights  of  the  animal  and  of  the 
calorimeter,  but  their  several  capacities  for  heat.  In  the  case 
in  which  the  temperature  of  the  animal  remains  the  same,  the 
amount  of  production  being  equal  to  that  of  discharge,  all 
that  is  required  is  to  know  how  much  heat  has  been  communi- 
cated during  the  period  of  observation  to  the  calorimeter.  In 
the  opposite  case  we  must,  in  order  to  judge  of  the  quantity 

1  I  have  lately  adopted  a  better  method  of  agitation,  consisting  in  the 
injection  of  air  into  the  space  below  the  chamber  A.  The  construction 
is  such  that  the  whole  of  the  air  so  used  finds  its  way  into  the  chamber. 


BY   DR.    BURDON-SANDERSON.  341 

of  heat  produced,  add  to  or  deduct  from  the  quantity  commu- 
nicated the  quantity  it  has  borrowed  or  given  off  from  its  own 
body.  If  the  animal  loses  heat  while  it  is  in  the  chamber, 
the  "heat  it  gives  off  is  only  partially  generated,  the  remainder 
being  abstracted  from  its  own  body.  If  it  gains,  the  quantity 
of  heat  generated  is  only  partially  given  off;  the  remainder  is 
added  to  its  own  temperature.  To  make  this  deduction  or 
addition,  as  the  case  may  be,  two  questions  must  be  answered. 

1.  How  much  heat  does  the  calorimeter  require  in  order  that 
its  temperature  may  be  raised  one  degree? 

2.  How  much  does  the  bodjr  of  the  animal  require  for  the 
same  purpose  ? 

In  both  cases  the  quantity  required  is  equal  to  the  specific 
heat  multiplied  by  the  weight.  The  mean  specific  heat  of  the 
calorimeter  is  obtained  by  adding  together  the  products  of  the 
specific  heat  and  weight  of  the  parts  of  which  it  is  composed 
— i.  <?.,  the  iron  case  and  the  water. 

Supposing,  e.  g.,  the  iron  to  weigh  3800  grammes  and  the 
*water  8600  grammes,  the  specific  heat  of  iron  being  0.114,  the 
product  in  question  is  for  the  iron  casing  419.5,  while  that  for 
the  water  is  8600.0.  Consequently  9019.5  gramme-units'  of 
heat  are  required  to  raise  the  whole  one  degree  of  temperature. 
Apptying  the  same  method  to  the  animal  body,  the  specific 
heat  of  which  is  estimated  to  be  0.83,  we  have  of  course  0.83 
gramme-units  as  the  quantity  to  be  added  or  deducted  for  each 
gramme  of  weight  and  degree  of  variation  of  temperature. 

The  whole  process  will  be  readily  understood  from  an  ex- 
ample, the  weight  of  the  calorimeter  being  that  given  above. 

Temperature  of  calorimeter — at  beginning  9°.l  C,  at  end 
9C.7  C. 

Temperature  of  animal — at  beginning  39°.2  C,  at  end 
38°.3  C. 

Weight  of  animal,  3200  grammes. 

From  these  results  we  obtain  : — 

1.  Units  of  heat  communicated  to  the  calorimeter  9019.5  x 

1.6  =  14431. 

2.  Units  of  heat  borrowed  from  the  body  of  the  animal 

3200  x  0.83  x  0.9  =  2390. 
Result  14431  —2390  =  12041. 

That  is  to  say,  the  animal,  during  the  period  of  observation 
gave  off  12,041  gramme-units  of  heat. 

In  calorimetrical  experiments,  the  temperature  of  the  water 

1  The  absolute  amount  of  heat  (in  gramme-units)  required  to  raise 
the  calorimeter  1°  C.  of  temperature  may  be  ascertained  empirically  by 
introducing  into  the  calorimeter  (in  place  of  the  animal)  a  metal  vessel 
containing  a  known  weight  of  water  at  a  known  temperature — say  40° 
C. — and  determining  on  the  one  hand  the  loss  of  heat  sustained  by  the 
water,  and  on  the  other,  the  gain  by  the  calorimeter  in  a  given  time. 


342  ANIMAL    HEAT. 

should,  as  a  rule,  be  a  little  higher  than  that  of  the  surround- 
ing atmosphere.  Not  only  is  this  the  condition  most  favour- 
able to  the  accuracy  of  the  observations,  but  it  is  most  advan- 
tageous as  regards  the  state  of  the  animal  observed.  If  the 
temperature  is  too  high,  the  disengagement  of  heat  from  the 
surface  is  relatively  lessened,  so  that  unless  completely  com- 
pensated for  b}-  increased  evaporation,  the  bodily  temperature 
of  the  animal  will  rise.  If,  on  the  other  hand,  the  tempera- 
ture of  the  calorimeter  is  lower  than  that  of  the  surrounding 
air,  that  of  the  animal  sinks  so  quickly  that  its  condition  is 
no  longer  normal.  It  is  obviously  of  great  importance  that 
the  observations  should  be  made  in  a  room  of  even  tempera- 
ture, and  it  is  desirable  that  it  should  not  be  too  cold. 

The  method  above  described  may  be  applied  not  only  to  the 
investigation  of  periodical  and  other  physiological  variations 
of  the  process  of  nutrition,  but  to  the  investigation  of  many 
abnormal  states  and  alterations,  such  for  example  as  those  of 
fever  changes  affecting  the  condition  of  the  surface  of  the 
body,  changes  affecting  the  circulation,  respiration  or  nervous" 
system,  and  changes  produced  by  the  action  of  various  drugs.1 
— For  the  investigation  of  fever,  the  pyrexial  state  may  be  pro- 
duced experimentally,  either  by  injecting  into  the  venous  sys- 
tem small  quantities  (5  to  15  minims)  of  the  exudation  liquids 
of  certain  acute  inflammations;  or  by  producing  a  local  in- 
flammation, e.  (/.,  by  applying  croton  oil  to  the  surface.  Al- 
though the  increase  of  temperature  produced  bj*  these  methods 
has  been  carefully  investigated  by  the  thermometer,  no  suffi- 
cient investigations  have  as  yet  been  made  as  to  the  quantit}' 
of  heat  produced  in  a  given  time.  Among  other  subjects 
which  admit  of  calorimetrical  investigation,  that  of  the  remark- 
able effects  produced  in  rabbits  by  the  process  of  "  varnish- 
ing" may  be  referred  to. 

111.  Increased  Discharge  of  Heat  of  "Varnished" 
Rabbits. — It  is  well  known  that  rabbits  when  smeared  over 
the  clipped  surface  with  gelatin  or  any  other  similar  material, 

1  Considering  that  it  is  not  possible,  even  with  the  utmost  care,  to 
keep  the  animal  in  a  perfectly  natural  condition  during  a  calorimetrical 
observation,  and  that  there  are  certain  sources  of  error  inseparable  from 
the  method  itself,  which  do  not  admit  of  being  corrected  for,  it  is  advi- 
sable in  employing  the  calorimeter  for  physiological  investigations  to 
estimate  the  value  of  the  results  obtained  not  by  calculation  but  by 
comparative  experiments,  e.  g.,  (1)  by  comparing  the  result  obtained 
under  the  condition  to  be  investigated  with  the  result  obtained  in  the 
normal  state  of  the  same  animal  ;  (2)  by  employing  in  each  observation 
two  calorimeters,  in  one  of  which  the  animal  is  placed,  while  the  other 
remains  unoccupied,  but  in  all  other  respects  under  the  same  conditions. 
In  this  case,  the  loss  of  heat,  if  any,  during  the  period  of  observation 
in  the  empty  calorimeter  is  to  be  added  to  the  gain  in  the  one  in  which 
the  animal  is  contained. 


X 

BY    DR.    BURDON-S ANDERSON.  343 

die  ;  the  pulse  and  respiration  being  first  accelerated  and  then 
diminishing.  Associated  with  this  last  change  is  a  veiy  rapid 
loss  of  temperature,  while  the  urine  becomes  albuminous. 
Formerly  it  was  supposed' that  these  changes  were  dependent 
on  the  suspension  of  respiration.  It  is  easy,  however,  to  prove 
experimentally  that  it  is  not  so  by  placing  the  animal  in  a 
chamber  at  a  temperature  of  about  30°  C,  when  it  is  seen 
that  as  the  temperature  of  the  body  rises  the  other  symptoms 
disappear.  Even  if  the  animal  has  been  allowed  to  cool  as 
low  as  21°.l  C.  it  can  be  restored  by  warmth.  By  placing  a 
varnished  rabbit  in  the  calorimeter,  it  can  be  shown  that  al- 
though its  temperature  is  actually  10°  or  more  below  that  of 
the  surrounding  air,  it  gives  off  a  great  deal  more  heat  than  a 
normal  rabbit.  Thus  I  find  that  a  rabbit,  which  in  the  normal 
state  gives  off  only  3000  heat  units  in  ten  minutes,  gives  off 
about  20,000  after  varnishing,  notwithstanding  that  in  the 
former  case  its  temperature  was  constant  at  39.5°  C,  while  in 
the  other  it  sank  from  36 c  to  25°. 

Section  II. — Thermometry. 

The  temperature  of  the  animal  body  is  measured  either  by 
the  mercurial  thermometer  or  thermo-electrically  : — 

118.  Measurement  of  Temperature  by  the  Mercu- 
rial Thermometer. — The  mercurial  thermometer  used  for 
ph}-siological  (as  well  as  for  pathological)  purposes  should 
have  the  following  characters.  The  proportion  between  the 
quantity  of  mercury  contained  in  the  bulb  and  the  lumen  of 
the  tube  must  be  such  that  the  difference  of  length  of  the 
column  produced  by  any  given  increase  of  temperature  shall 
be  as  great  as  possible.  One  degree  of  the  centigrade  scale 
should  be  sufficiently  distant  from  another  to  render  it  possi- 
ble to  read  easily  to  a  tenth.  On  this  account  the  range  of 
graduation  is  necessarily  limited.  It  is  sufficient  if  it  extends 
from  30°  to  45°  C.  The  bulb  must  expose  a  large  surface  in 
proportion  to  the  volume  of  mercury  it  contains  ;  for  which 
reason  it  is  made  cylindrical.  The  most  celebrated  thermo- 
meters are  those  of  Dr.  Geissler,  Of  Bonn.  They  are  32  centi- 
metres (  =  12  inches)  long,  and  relatively  exceedingly  narrow 
— only  a  line  and  a  half  in  diameter.  The  cistern  is  no  wider 
than  the  stem,  and  is  eight-tenths  of  an  inch  long.  Mr.  Hawks- 
ley,  of  Blenheim  Street,  has  recently  constructed  for  me  in- 
struments which  are  very  similar  and  comparable  in  quality 
to  those  of  (Teissier.  The  bulbs  and  stems  are  of  equal  diame- 
ter throughout,  not  exceeding  three  millimetres.  They  are 
extremely  sensitive,  and  the  graduation  is  so  fine  that  to  the 
practised  observer  it  is  easy  to  read  accurately  to  the  50th  of 
a  degree  of  Celsius. 


344  ANIMAL    HEAT. 

For  many  purposes,  it  is  desirable  to  employ  maximum  ther- 
mometers, ?.  e.,  thermometers  in  which  the  capillary  tube  pos- 
sesses a  narrowing  at  one  part,  which,  while  it  allows  the  mer- 
cury to  ascend,  prevents  its  return  to  the  cistern  ;  so  that  the 
instrument,  wdien  removed  from  the  part,  still  shows  the  tem- 
perature to  which  the  bulb  has  been  exposed.  Maximum 
thermometers  are  constant^  used  for  clinical  purposes  in  this 
country,  and  are  also  valuable  to  the  physiologist. 

If  it  is  intended  to  observe  the  temperature  in  the  interior 
of  the  heart,  or  in  any  of  the  great  cavities  of  the  bod}-,  the 
animal  must  be  of  large  size,  and  must  be  curarized.  To  ob- 
serve the  temperature  in  the  right  ventricle,  the  bulb  of  a  long 
stemmed  thermometer  must  be  introduced  through  the  exter- 
nal jugular.  To  observe  that  of  the  aorta,  or  left  ventricle, 
the  carotid  must  be  opened.  If  a  large  dog  is  used,  a  thermo- 
meter introduced  into  the  right  side  of  the  heart  ma}-,  if  the 
tube  be  long  enough,  be  easily  pushed  onwards  into  the  vena 
cava.  In  the  rabbit  it  is  scarcely  possible  to  do  this,  but  it  is 
easy  with  one  of  the  thermometers  mentioned  above  to  mea- 
sure the  temperature  of  the  heart  in  this  animal. 

119.  Electrical  Measurement  of  Temperature. — If 
a  magnetic  needle  is  set  in  an  oblong  quadrangular  frame,  of 
which  one  of  the  long  sides  is  of  bismuth  and  the  other  three 
sides  are  of  copper,  the  two  metals  being  soldered  together  at 
the  two  junctions  in  such  a  manner  that  the  needle  can  swing 
freely  in  a  plane  at  right  angles  to  that  of  the  frame,  and  so 
placed  that  the  frame  is  in  the  magnetic  meridian,  it  can  then 
be  observed  that  if  one  of  the  junctions  is  warmed,  the  magnet 
is  made  to  decline  from  its  normal  position — the  degree  of 
deflection  varying  with  the  difference  of  temperature  of  the  two 
junctions,  and  continuing  until  they  again  resume  the  same 
temperature.  The  deflection  of  the  magnet  indicates  that  in 
the  quadrangle  a  current  exists,  and  the  direction  of  the  de- 
flection shows  that  the  current  flows  from  the  bismuth  to  the 
copper,  beginning  at  the  warmer  of  the  two  junctions.  Similar 
results  are  obtained  when  other  combinations  of  two  metals 
are  substituted  for  bismuth  and  copper.  According  to  the 
electro-motive  force  yielded  by  each,  the  metals  may  be  ar- 
ranged in  what  is  called  the  thermo-electrical  series  ;  in  which 
series  those  metals  are  placed  furthest  apart  which  3'ield  the 
greatest  quantity  of  electricity  at  their  junctions.  Bismuth  is 
at  one  end,  antimony  at  the  other  ;  close  to  bismuth  comes 
German  silver,  and  close  to  antimoii}7  iron.  Iron  and  German 
silver  yield,  therefore,  nearly  as  much  electro-motive  force  per 
degree  of  difference  of  temperature  as  antimony  and  bismuth, 
and  are  much  more  workable.  Being  further  apart  in  the 
thermo-electrical  series  than  bismuth  and  copper,  they  are 
preferable  to  those  metals  on  that  ground  also. 


BY    DR.    BURDON-SANDERSON.  345 

On  these  facts  are  based  the  electrical  method  of  measuring 
temperature.  Instead  of  the  quadrangle,  we  give  to  our  junc- 
tions a  convenient  form  for  introducing  them  into  the  situa- 
tions at  which  we  desire  to  make  our  measurements.  Instead 
of  the  magnet,  we  use  the  instrument  known  as  a  multiplier. 
This  consists  essentially  of  a  magnet,  surrounded  by  numerous 
coils  of  copper  wire,  in  which  the  current  due  to  difference  of 
temperature  between,  the  two  junctions  flows.  We  have  to  de- 
scribe first  the  junctions,  then  the  multiplier.  As  one  of  the 
reasons  for  preferring  the  electrical  to  the  ordinary  method  of 
measurement  is  that  the  measuring  instrument  can  be  intro- 
duced with  exactitude  into  spaces  which  are  too  small  for  a 
thermometer  bulb,  the  form  usually  given  to  the  junctions  is 
that  of  a  needle.  These  needles  are  generally  made  of  iron  and 
German  silver,  i.  e.,  each  needle  consists  of  two  wires  of  iron 
and  German  silver  respectively,  which  are  soldered  together  at 
and  near  their  points,  so  that  the  junction  may  be  completely 
buried  in  any  tissue  into  which  the  needle  is  thrust.  The  two 
needles  forming  one  element  are  connected  together,  metal  to 
metal — the  iron  wire  forming  part  of  both,  while  the  two  Ger- 
man silver  wires  communicate  each  with  the  two  ends  of  the 
coil  of  the  multiplier,  thus  completing  the  circuit.  As  the 
needles  require  to  be  handled  by  the  experimenter,  it  is  neces- 
sar}'  to  protect  the  upper  ends  by  covering  them  with  silk  and 
varnish  ;  and  the  two  wires  must  be  carefully  isolated  from 
each  other  everywhere  excepting  at  the  points  where  they  are 
soldered  together. 

For  the  purpose  of  making  clear  the  mode  of  using  the  ther- 
mo-electric needles,  let  us  suppose  that  it  is  required  to  measure 
the  difference  of  temperature  between  two  symmetrical  parts 
on  opposite  sides  of  the  bod}7,  one  of  which  is  inflamed,  the 
other  in  the  normal  state.  One  or  any  number  of  thermo-ele- 
ments  may  be  used,  each  of  which  consists  of  a  pair  of  needles 
with  their  wires  arranged  as  above  described.  If  only  one  ele- 
ment is  employed,  one  of  its  junctions  is  placed  in  each  of  the 
tissues  of  which  the  temperature  is  to  be  investigated  ;  the  iron 
wire  of  each  needle  being  in  communication  with  that  of  the 
other,  and  the  German  silver  wires  with  the  ends  of  the  multi- 
plier. If  several  pairs  are  used,  an  equal  number  of  needles 
must  be  placed  in  each  of  the  parts  to  be  compared,  the  ar- 
rangement of  which  is  as  follows :  Let  us  designate  the  needles 
on  the  right  side  a,  b,  c,  those  on  the  left  a',  b',  and  c'.  The 
German  silver  ends  of  a  and  c'  being  connected  with  the  multi- 
plier, the  iron  end  of  a  is  connected  with  that  of  a',  the  iron 
end  of  b  with  that  of  b',  and  that  of  c  with  c',  and  the  German 
silver  end  of  a'  with  that  of  b,  and  that  of  b'  with  that  of  c. 
It  is  scarcely  requisite  to  say  that  the  junctions  need  not 
assume  the  form  of  needles ;  each  may  consist  of  two  wires  of 


346  ANIMAL    HEAT. 

different  metals  soldered  together  endwise,  in  which  case  it  is 
of  course  necessary  to  transfix  the  part  to  be  investigated  with 
the  joined  wire,  placing  it  in  such  a  position  that  the  junction 
is  at  the  point  to  be  investigated. 

The  multiplier  consists  essentially  of  a  magnetic  needle,  sus- 
pended horizontally  in  the  centre  of  a  coil  of  wire  along  which 
flows  the  current  which  requires  to  be  measured.  In  conse- 
quence of  this  arrangement,  the  needle,  if  it  is  in  the  same 
plane  with  the  coil  which  surrounds  it,  will  be  deflectdl  in 
accordance  with  Ampere's  law,  whenever  a  current  passes  along 
the  wire,  and  will  be  acted  on  similarly  by  all  parts  of  the  coil. 
In  order  to  enable  the  needle  to  act  under  the  direction' of  the 
coil  without  being  affected  by  terrestrial  magnetism,  it  is  made 
astatic.  Twomagnetic  needles  of  equal  powers,  placed  parallel 
to  each  other,  are  rigidty  united  by  a  copper  wire  passing 
through  their  centres  of  gravity  in  such  a  manner  that  the  north 
pole  of  the  one  is  opposite  the  south  pole  of  the  other,  and  vice 
versa.  The  united  needles  are  hung  at  such  a  level  that  the 
one  swings  above  the  coil,  the  other  in  its  centre.  From  this 
arrangement  it  results  not  only  that  the  influence  of  earth- 
magnetism  is  neutralized,  but  that  both  needles  are  affected  in 
the  same  way  by  the  current. 

The  construction  of  the  most  important  parts  of  the  instru- 
ment (which  is  represented  in  fig.  265,  bis)  is  as  follows :  The 
wire  is  coiled  round  a  frame  of  wood,  represented  at  a,  the  two 
pieces  x  and  y  are  hollow.  In  the  cavity  of  the  horizontal 
piece,  x,  the  lower  of  the  two  magnets  swings,  and  can  be 
introduced  through  the  vertical  slit  in  y.  The  magnets  are 
shown  at  b.  The  copper  wire  is  carefully  covered  with  silk, 
and  varnished.  As  the  resistance  of  the  coil  must  be  low,  the 
wire  is  not  longer  than  from  20  to  25  feet,  and  its  thickness  is 
considerable  (0.5-1  millim.).  The  end  of  the  coil  terminates 
in  the  screws  seen  on  the  right  side  in  the  drawing.  The  nee- 
dles are^hung  by  a  cocoon  fibre  to  the  centre  of  the  frame,  the 
mode  of  attachment  being  such  that  by  raising  or  depressing 
the  knob  the  height  at  which  they  are  suspended  can  be  varied. 
When  the  instrument  is  used,  the  lower  needle  must  swing 
freely  in  the  horizontal  split,  the  upper  above  the  graduated 
circle.  Having  raised  the  needles  by  the  cocoon  fibres  till  they 
swing  freely,  adjust  the  instrument  with  the  levelling  screws  so 
that  the  fibre  hangs  exactly  in  the  centre  of  the  circle,  then 
rotate  the  coil  until  the  upper  needle  points  to  180°  and  0°, 
and  connect  the  screws  with  the  thermo-elements,  with  the 
intervention  of  a  single  "plug-key."  If  the  temperatures  of 
the  junctions  are  different,  the  needle  is  deflected  on  opening 
the  key. 

In  using  the  multiplier,  it  must  be  remembered  that  although 
the  deflection  of  the  needle  varies  with  the  intensity  of  the  cur- 


BY    DR.    BURDON-SANDERSON.  347 

rent,  find  consequently  with  the  difference  of  temperature  be- 
tween the  two  junctions,  the  variations  are  not  proportional,  so 
that,  e.  g.,  a  deflection  of  30°  does  not  indicate  a  current  twice 
as  strong  as  a  deflection  of  15°.  The  relation  between  the  read- 
ings and  the  intensities  of  the  currents  they  indicate  is  different 
in  each  instrument,  and  consequently,  must  be  determined  once 
for  all  for  each.  Of  the  various  modes  which  may  be  adopted 
for  this  purpose,  the  simplest  is  the  empirical  method  devised 
originally  b}r  Melloni,  an  account  of  which  will  be  found  in  all 
treatises  on  physics  ;  the  operation  can  be  best  done  in  a  physi- 
cal laboratory.  Within  twent}'  degrees  the  deflection  is  usu- 
ally so  nearly  proportional  to  the  strength  of  the  current,  that 
the  error  may  be  disregarded.  For  deflections  beyond  this 
point  the  results  of  the  graduation  must  be  recorded  in  a  table 
of  the  following  form,  which  must  be  kept  with  the  instrument. 

Deflection.  Intensity  of  Current. 

20°  .                         20.0 

24°  25.0 

28°  31.5 

32°  39.6 

36°  49.5 

etc.  etc. 

The  above  numbers  are  taken  from  the  example  given  by 
Melloni.  In  the  second  column  the  starting  number  20,  stands- 
for  the  intensity  of  current  indicated  by  a  deflection  of  20°. 
This  being  assumed,  the  other  numbers  represent  the  intensities 
corresponding  to  the  deflections  opposite  to  which  they  stand. 

The  instrument  having  been  graduated,  it  is  still  necessary 
to  determine  for  each  element  the  constant,  by  which  the  start- 
ing number  must  be  multiplied  in  order  to  give  the  temperature 
difference.  Thus,  if  with  a  certain  element  a  deviation  of  20° 
is  produced  by  a  difference  of  temperature  amounting  to  0.10 
C,  the  temperature  corresponding  to  any  other  deviation  is 
obtained  by  multiplying  the  number  opposite  to  it  in  the  table 
by  0.005,  which  is  therefore  the  constant  required.  This  deter- 
mination the  physiologist  must  make  for  himself.  It  is  effected 
by  immersing  the  junctions  into  two  large  vessels  containing 
water  or  oil,  the  difference  of  temperature  between  which  is 
measured  by  accurate  and  sensible  thermometers.  To  avoid 
error,  it  is  of  course  necessary  to  repeat  the  observation  many 
times. 

[For  the  accurate  measurements  of  temperature  which  are 
required  in  some  physiological  and  pathological  researches  the 
multiplier  is  not  adapted.  We  substitute  for  it  a  true  galvano- 
meter. The  instrument  used  in  Germany  is  the  Spiegelbussole 
of  Wiedemann,  a  description  of  which  will  be  found  in  Rosen- 
thal's  "  Electricitatslehre  fur  Mediciner."      In  England,  the 


348  ANIMAL    HEAT. 

preference  is  given  to  the  galvanometer  of  Sir  William  Thom- 
son. In  both  of  these  instruments  the  deviation  of  the  needle 
has  a  definite  relation  to  the  intensity  of  the  current,  the  inten- 
sities of  any  two  currents  being  proportionate  to  the  tangents 
of  the  angles  of  the  deviation  they  produce;  so  that,  so  long 
as  the  same  junctions  are  used,  if  the  deviation  produced  by 
an}'  known  difference  of  temperature  has  been  ascertained  em- 
pirically, the  values  of  other  readings  can  be  deduced  from  it.] 
120.  Distribution  of  Temperature  in  the  Body. — The 
principal  purpose  to  which  the  therm o-electrical  method  is 
applied  in  physiology,  is  that  of  measuring  the  differences  of 
temperature  which  exist  between  different  parts  of  the  body. 
These  differences  vary  according  to  the  proximity  to,  or  dis- 
tance from,  the  surface  of  the  point  where  the  measurement  is 
made,  and  according  to  the  supply  of  blood  which  the  adjacent 
tissues  or  organs  receive.  Taking  as  a  standard  of  comparison 
the  temperature  of  blood  in  the  aorta,  the  facts  hitherto  ascer- 
tained as  to  the  temperature  of  other  parts  are  as  follows: — 

1.  The  blood  of  the  inferior  vena  cava  is  warmer,  that  of  the 
superior,  colder  ;  but  in  the  former  this  is  true  only  of  the 
upper  part  of  the  vein  just  as  it  passes  through  the  diaphragm. 

2.  The  temperature  of  the  skin  and  subcutaneous  tissue  is 
always  considerably  lowrer  than  that  of  the  aorta,  but  varies  a 
good  deal. 

3.  The  temperature  of  the  lungs  also  varies.  Near  the  dia- 
phragm it  is  higher  than  that  of  the  aortic  blood,  but  elsewhere, 
and  particularly  near  the  costal  surfaces,  it  is  lower. 

4.  All  the  abdominal  organs  have  a  higher  temperature  than 
that  of  the  aortic  blood,  those  in  the  upper  part  of  the  abdomi- 
nal cavity  being  the  warmest. 

5.  The  blood  contained  in  the  right  ventricle  is  somewhat 
warmer  than  that  in  the  left,  the  difference  varying  from  1°  C. 
to  3°  C.  This  difference  is  not  dependent  on  the  cooling  of  the 
blood  as  it  passes  through  the  lungs;  for  it  is  just  as  marked 
when  an  animal  is  made  to  breathe  warmed  air  saturated  with 
moisture.  Moreover,  such  an  hypothesis  is  rendered  untenable, 
by  the  fact  that  the  lungs  themselves  are  scarcely  cooler  than 
the  blood  in  the  aorta.  Its  real  cause  is,  doubtless,  that  the 
wall  of  the  right  ventricle  is  in  contact  with  the  diaphragm  and 
abdominal  organs,  while  the  left  is  surrounded  by  lung. 

The  recent  introduction  of  thermometers  of  extreme  sensi- 
tiveness and  accuracy  has  rendered  the  method  less  important 
to  the  physiologist  than  it  seemed  to  be  a  few  years  ago.  This 
may  be  illustrated  by  the  remarkable  fact,  that  the  long  con- 
troversy as  to  the  relative  temperature  of  the  two  sides  of  the 
heart  has  been  at  last  set  at  rest,  not  electrically,  but  by  the 
thermometer. 


PHYSIOLOGY. 

PART  II.— FUNCTIONS  OF  MUSCLE  AND  NERVE. 
By  Dr.  MICHAEL  FOSTER. 


INTRODUCTORY. 

In  the  following  part  of  this  work,  the  object  chiefly  kept  in 
view  has  been  to  limit  the  directions  as  much  as  possible  to 
such  observations  and  experiments  as  the  student  may  be 
reasonably  expected  to  perform  for  himself  under  due  super- 
vision. The  ordinary  phenomena  of  muscle  and  nerve  are 
consequent^  dealt  with  at  far  greater  length  than  are  the 
properties  of  the  central  nervous  system.  The  latter  are,  to 
say  the  least,  but  imperfectly  known,  the  experiments  on  which 
our  knowledge  rests  difficult  and  complex,  and  too  often  bring- 
ing out  uncertain  or  even  contradictory  results.  The  former, 
on  the  other  hand,  may  be  studied  with  approximate  exacti- 
tude ;  the  methods  of  experiment  and  observation  are  becom- 
ing, year  by  year,  more  physical  in  character,  and  the  observa- 
tions themselves,  fundamental  in  their  nature  and  having  the 
widest  bearings  in  all  the  higher  branches  of  physiology,  may, 
for  the  most  part,  be  conducted  on  frogs,  may  be  repeated  any 
number  of  times  without  difficulty  or  expense,  and  so  serve 
usefully  as  a  means  of  training  students  in  physiological  study 
and  inquiry.  The  phenomena  in  question  are  so  fully  treated 
of  in  various  text-books,  that  space  in  the  following  chapters 
has  been  devoted  to  detailed  instructions  as  to  how  to  proceed 
in  the  various  observations  rather  than  to  complete  explana- 
tions of  what  the  observations  are  intended  to  show  or  prove. 

Instructions  concerning  the  various  special  pieces  of  appara- 
tus required  in  this  part  of  the  subject  are  thrown  together, 
for  convenience  sake,  in  the  first  chapter.  The  succeeding 
chapters  deal  with  the  general  properties  of  muscle  and  nerve; 
while  such  observations  as  the  student  may  be  expected  to 


350  GENERAL    DIRECTIONS. 

make  on  the  central  nervous   system  are  contained  in  the  two 
last  chapters. 

No  special  chapters  on  the  senses  have  been  introduced,  as 
there  seemed  to  be  no  mean  between  the  common  simple 
observations  on  the  one  hand  which  are  found  in  all  the  text- 
books and  such  elaborate  instructions  on  the  other  as  would 
hardly  come  under  the  scope  of  this  work. 


CHAPTER  XIX. 
GENERAL  DIRECTIONS. 

I.  The  Nerve-Muscle  Preparation. — Having  pithed  a 
frog  and  destroyed  both  its  brain  and  spinal  cord,  lay  it  on  its 
bell}'  and  make  an  incision  through  the  skin  along  the  middle 
line  of  the  back  of  the  thigh,  from  the  knee  to  the  end  of  the 
coccyx,  and  carry  the  incision  along  the  back  about  midway 
between  the  coccyx  and  ileum  (fig.  266,  line  &,  m,  n).  On 
drawing  back  or  removing  the  skin,  there  will  come  into  view, 
on  the  outside  of  the  thigh,  the  triceps  femoris  (fig.  267  a), 
on  the  median  side  the  semi-membranosus  c,  and  between  these 
the  small  narrow  biceps  femoris  b.  With  the  "  seeker"  sepe- 
rate  gently  b  and  c ;  the  sciatic  nerve  and  femoral  vessels  will 
be  found  running  between  them.  Gently  tear  away,  with  the 
seeker,  the  connective  tissue  round  the  nerve,  beginning  near 
the  knee  (where  it  divides  into  two  branches),  and  working 
upwards  till  the  muscle  n  is  reached.  Be  careful  to  touch  the 
nerve  itself  as  little  as  possible,  and  on  no  account  seize  it 
with  a  pair  of  forceps.  Carefully  cut  through  the  pyrilbrm 
muscle  n  and  the  connective  tissue  in  which  the  nerve  is  em- 
bedded at  this  point,  divide  the  iliac-coccygeal  muscle  d,  right 
through,  and  follow  the  three  nerves  (which  come  into  view 
when  the  muscle  is  removed,  and  which  go  to  form  the  sciatic 
and  other  nerves)  right  up  to  the  vertebral  column.  Cut  the 
column  across  just  above  the  last  lumbar  vertebra,  and  bisect 
lengthways  the  piece  so  cut  off.  Hold  the  bony  fragment  with 
the  forceps,  lift  it  up  and  free  it  from  the  tissues  around,  and 
then  follow  with  the  scissors  the  nerves  right  down  to  the 
knee,  cutting  away  their  various  branches  and  removing  any 
tissue  which  still  may  be  clinging  to  them. 

Now  remove  the  skin  from  the  leg;  the  gastrocnemius  (fig. 
267  g)  will  at  once  be  recognized  :  cut  through  the  tendo 
Achillis  at  /,  below  the  thickening  at  the  heel.  Holding  the 
cut  tendon  with  a  pair  of  forceps,  it  will  be  easy,  with  a  few 


BY    DR.    MICHAEL    FOSTER.  351 

strokes  of  the  seeker,  to  free  the  muscle  right  up  to  its  at- 
tachment to  the  end  of  the  femur,  at  h.  The  branch  of  the 
sciatic  nerve  going  to  the  gastrocnemius  will  be  readily  seen 
when  the  muscle  is  turned  over,  as  also  another  branch  which 
runs  along  its  under  surface,  but  which  ends  in  other  muscles. 
Carefully  avoiding  any  injury  to  the  former  nerve,  but  disre- 
garding the  latter,  cut  away  the  whole  of  the  tibia  and  fibula 
from  the  femur.  Clear  away,  carefully  avoiding  the  nerve,  all 
the  muscles  of  the  thigh  from  the  lower  end  of  the  femur  so 
as  to  leave  the  bone  tolerably  bare,  and  cut  the  bone  across  at 
its  lower  third.  There  is  left  merely  the  end  of  the  femur,  to 
which  is  attached  the  uninjured  gastrocnemius,  with  the  whole 
length  of  the  nerve  from  the  muscle  up  to  its  entrance  into 
the  spinal  canal.  The  muscle  attached  to  the  fragment  of 
femur,  with  its  prepared  nerve,  is  represented  in  fig.  268. 
(The  vertebral  fragment  is  not  shown.) 

II.  The  Lever. — In  order  to  study  the  contraction  of  a 
muscle,  it  is  advantageous  to  employ  a  lever. 

The  myographion  of  Helmholtz  and  Pfluger  is  shown  in  fig. 
269.  The  lever  a  moves  on  the  fulcrum  b  and  is  balanced  by 
the  counterpoise  c.  At  d  is  either  a  fine  brush  to  write  on 
paper,  or  a  fine  style  to  scratch  smoked  glass  or  paper.  The 
rod  e  bearing  the  style,  moves  on  a  hinge  at/*,  and  also  carries 
a  counterpoise  g.  Hence  the  writing  point  describes  a  straight 
line,  while  the  actual  end  of  the  lever  itself  is  describing  the 
arc  of  a  circle.  The  silk  thread  coming  from  the  tendon  of 
the  muscle  is  attached  at  h.  The  small  pan  is  to  receive 
weights  for  loading  the  muscle. 

For  ordinary  purposes,  the  simple  lever  of  Marey,  shown  in 
the  lower  part  of  fig.  270,  is  much  more  convenient  for  use, 
while  at  the  same  time  the  momentum  of  the  heavy  lever  of 
the  myographion  is  avoided.  The  portion  next  to  the  fulcrum 
is  of  metal,  perforated  or  notched  to  receive  the  hooks,  etc., 
by  which  the  muscle  is  attached  above,  and  the  weight  below. 
This  is  prolonged  by  a  thin  slip  of  wood  or  piece  of  straw,  at 
the  end  of  which  is  a  fine  brush,  placed  horizontally  at  an 
angle  of  about  60  degrees  to  the  long  axis  of  the  lever,  or  a 
thin  slip  of  gutta-percha  bearing  a  fine  needle  for  tracing  on 
smoked  glass  or  paper. 

To  get  rid  of  the  momentum,  the  weight  may  be  replaced 
by  a  long  weak  spiral  spring.  This  spring  must  be  graduated 
beforehand,  i.  e.,  the  amount  of  force  determined  which  is  re- 
quired to  extend  it  to  a  given  amount.  The  spiral  may  be 
replaced  by  a  simple  slip  of  main-spring  pressing  on  the  lever 
in  a  direction  opposite  to  that  of  the  movement  given  to  it  by 
the  muscle. 

III.  The  Moist  Chamber. — In  order  to  prevent  the 
muscle   and  nerve   from   drying,  they   must   be   kept   damp. 


352  GENERAL   DIRECTIONS. 

Moistening  either  muscle  or  nerve,  and  especially  the  nerve, 
even  with  Na.  CI.  .75  p.  c.  is  undesirable,  as  it  tends  to  intro- 
duce errors.  It  is  necessary,  therefore,  so  to  place  the  nerve 
and  muscle  that  they  may  be  experimented  upon  in  an  atmo- 
sphere kept  uniformly  damp.  This  is  effected  by  means  of 
the  moist  chamber  (fig.  270). 

This  consists  of  a  platform  of  hard  wood  or  ebonite,  which 
slides  up  and  down,  and  can  also  be  turned  from  side  to  side 
and  clamped  in  any  position,  on  an  upright.  Let  into  the 
platform  are  two  or  more  pairs  of  insulated  binding  screws  for 
receiving  the  various  wires  for  the  electrodes,  as  well  as 
clamps  into  which  the  leaden  electrode  bearers  are  fixed.  The 
upright  on  which  the  platform  slides  also  carries  above  a 
sliding  arm,  with  a  clamp  for  holding  the  femur  of  the  nerve- 
muscle  preparation,  and  below  a  similar  sliding  arm  to  which 
the  lever  is  fixed.  The  attachment  of  the  muscle  to  the  lever 
is  carried  through  a  slit  in  the  platform.  A  common  glass 
shade,  fitting  into  a  rim  in  the  platform,  covers  everything ; 
and  when  several  pieces  of  wet  blotting-paper  are  placed  inside 
the  cover,  the  atmosphere  within  may  be  kept  saturated  with 
moisture  for  any  length  of  time. 

IV.  Nerve  Chamber. — When  the  phenomena  of  electro- 
tonus  (Chap.  XXVII.)  are  being  studied,  it  is  very  desirable 
to  have  a  smaller  chamber  than  the  ordinal  moist  chamber  to 
work  in.  This  may  be  gained  by  having  a  small  glass  trough, 
about  three  inches  long  and  one  broad,  with  a  movable  top, 
and  the  glass  of  one  of  the  sides  replaced  by  a  piece  of  India- 
rubber  sheeting  with  a  slit  along  the  middle.  The  electrodes 
may  be  introduced  through  the  slit  at  the  side  (the  India- 
rubber  closing  on  them),  the  nerve  placed  in  position  on  the 
electrodes,  a  few  morsels  of  wet  blotting-paper  inserted  (so  as 
not  to  touch  the  nerve),  and  the  cover  laid  on.  The  nerve 
ma}'  thus  be  kept  from  drying  for  a  considerable  time. 

V.  Electrodes. — For  many  purposes  the  ends  of  the 
copper  wires  may  be  used  without  any  special  arrangement. 
The  two  wires  may  be  kept  separate,  or  they  may  be  fixed  at  a 
definite  distance  from  each  other  in  an  insulating  handle  of 
bone,  wood,  gutta-percha,  etc.  (fig.  271).  It  is  often  con- 
venient to  have  the  ends  of  wires  completel}'  covered,  except 
just  at  one  point  in  each  to  which  the  nerve  may  be  applied 
(fig.  271).  In  this  case  it  is  also  frequently  an  advantage  to 
have  the  ends  somewhat  curved.  Such  a  pair  of  electrodes 
can  easily  be  made  at  once  by  fastening  two  wires,  bent  as 
desired,  on  either  side  of  a  slip  of  wood,  or  other  non-conduct- 
ing material,  of  the  thickness  required  to  separate  the  wires 
sufficiently,  coating  the  whole  with  melted  paraffin,  and,  when 
the  paraffin  has  cooled,  scraping  a  little  away  at  one  spot  till 
a  point  of  each  wire  is  exposed.     Platinum  wire,  or  slips  of 


BY   DR.   MICHAEL   FOSTER.  353 

platinum   foil,   may  be   advantageous^   substituted   for   the 
terminal  portions  of  the  copper  wires. 

VI.  Non-Polarizable  Electrodes. — In  many  cases,  how- 
ever, it  will  be  absoluteljr  necessary  to  have  non-polarizable 
electi'odes.  The  most  convenient  form  is  that  of  Du  Bois 
Reymond,  modified  by  Donders  (fig.  212). 

A  glass  tube  a  (about  one-third  inch  diameter  is  the  most 
convenient  size)  is  plugged  at  one  end  by  a  plug  b  of  china 
clay,  worked  into  a  firm  putt}'  with  .75  p.  c.  sol.  of  Na.  CI. 
A  few  drops  of  a  saturated  solution  of  sulphate  of  zinc  c  are 
carefull}'  introduced  into  the  tube.  A  slip  of  zinc,  or  piece  of 
zinc  wire  2,  thoroughly  amalgamated  at  the  tip  but  covered 
with  varnish  over  the  greater  part  of  its  length,  is  introduced 
into  the  tube,  and  so  placed  that  the  amalgamated  end  dips 
into  the  zinc  solution  as  far  as  two  or  three  millimetres  above 
the  clay  plug.  The  other  upper  end  of  the  wire  is  bent  round 
the  upper  open  end  of  the  tube,  and  brought  to  the  binding 
screw  of  the  brass  collar  d,  which  is  movable  up  and  down  the 
outside  of  the  tube,  and  can  be  clamped  at  will.  The  copper 
wire  e  is  fastened  in  the  same  binding  screw. 

Several  such  electrodes  of  different  forms  should  be  pre- 
pared. The  tube  may  be  cut  off  straight  at  the  lower  end, 
and  the  clay  plug  brought  out  in  the  form  of  a  cone  (fig.  273 
a),  or  in  any  other  shape  that  may  be  desirable.  It  is  often 
convenient  that  the  end  of  the  tube  should  be  cut  obliquely, 
witli  the  clay  plug  not  projecting  at  all  (fig.  273  c).  The  end 
of  the  tube  ma}'  be  of  the  same  diameter  as  the  rest  of  the 
tube,  or  may  be  brought  more  or  less  to  a  point.  Where  the 
electrodes  require  to  be  applied  to  nerves,  it  is  convenient  to 
have  the  form  fig.  273  b  ;  the  end  of  the  tube  is  bent  round, 
and  the  extreme  point  closed ;  near  the  end,  on  the  upper 
surface,  a  small  hole  is  drilled  ;  consequently  the  plug  b  is  only 
exposed  at  b'. 

Electrodes  of  different  lengths  should  be  prepared ;  those 
required  for  working  in  the  moist  chamber  need  not  be  more 
than  two  inches  long ;  otherwise,  five  or  six  inches  is  a  con- 
venient length. 

The  most  convenient  electrode-bearer  is  represented  in  fig. 
272.  The  piece  of  leaden  wire  k  ends  in  the  brass  head  h', 
which  bears  the  two  arms  f  f,  each  of  which  holds  an  elec- 
trode tube  by  means  of  a  spring  collar.  The  two  arms  move 
round  the  point  //,  and  can  be  clamped  in  any  position.  The 
points  of  the  electrodes  may  thus  be  brought  near  to  or  apart 
from  each  other,  as  may  be  desired.  The  extremely  flexible 
but  non-elastic  leaden  wire  (a  cylindrical  wire  being  far  better 
than  a  flat  piece  of  lead),  the  far  end  of  which  is  fixed  in  a 
clamp,  permits  the  pair  of  electrodes  to  be  placed  without  re- 
23 


354  GENERAL    DIRECTIONS. 

bound,  and  therefore  with   great   accuracy,   in    any  position 
whatever. 

VII.  Commutator. — This  is  useful  for  changing  the  direc- 
tion of  a  current  when  the  effects  of  constant  currents  are 
being  studied.  Any  form  of  commutator  may  be  used,  pro- 
vided that  the  current  can  easil}-  be  cut  off  altogether,  as  well 
as  reversed  in  direction.  A  very  convenient  form  is  that 
represented  in  fig.  297,  in  which,  when  the  handle  is  horizontal, 
the  current  is  cut  off  from  the  electrodes  altogether;  and  a 
different  direction  given  to  the  current  according  as  the  handle 
is  raised  or  lowered.  The  wires  from  the  battery  should  be 
brought  to  the  upper,  and  those  from  the  electrodes  to  the 
lower  binding  screws. 

VIII.  Rheoehord. — This  instrument  is  directed  to  be  used 
in  the  following  pages  simply  for  the  purpose  of  causing  defi- 
nite changes  in  the  amount  of  a  constant  current  under  use. 
Fig.  298  represents  a  convenient  form  of  the  rheoehord  of  Du 
Bois  Reymond. 

Bring  the  wires  from  the  battery  to  the  binding  screws  at 
the  top  of  the  board  and  those  from  the  electrodes  to  the  same 
screws.  If  all  the  plugs  are  in  place  and  the  travelling  mer- 
cury cups  close  up  to  the  top  of  the  board  in  direct  contact 
with  the  brass,  the  resistance  to  the  current  from  the  battery 
offered  by  the  rheoehord  compared  with  that  offered  by  the 
circuit  of  the  electrodes  is  practically  nil,  and  consequently  all 
the  current  passes  through  the  former  and  none  through  the 
latter.  If  the  mercury  cups  be  moved  on  their  platinum  wires 
a  little  distance  down  the  board,  there  will  be  no  passage  for 
the  current  from  one  side  of  the  rheoehord  to  the  other,  ex- 
cept through  such  a  length  of  the  two  platinum  wires  as  lies 
between  the  cups  and  the  brass  plate.  But  these  thin  wires 
offer  a  certain  resistance  to  the  passage  of  the  current,  and 
consequently  a  proportionate  fraction  of  the  total  current  from 
the  battery  is  thrown  into  the  circuit  of  the  electrodes.  By 
sliding  the  mercury  cups  various  distances  down  the  graduated 
board,  small  differences  of  resistance  in  the  rheoehord  are  es- 
tablished, and  consequent!}'  slightly  differing  fractions  of  the 
total  current  thrown  into  the  circuit  of  the  electrodes.  If  one 
of  the  plugs  be  removed,  a  certain  amount  of  resistance  is 
suddenl}'  introduced  into  the  rheocord,  and  consequently  a 
certain  amount  of  the  current  is  suddenty  thrown  into  the 
circuit  of  the  electrodes.  With  the  different  plugs  different 
amounts  of  resistance  are  introduced  into  the  rheoehord,  and 
different  amounts  of  the  current  thrown  into  the  circuit  of  the 
electrodes.  The  several  plugs  are  all  numbered  as  multiples 
of  the  resistance  offered  by  the  total  length  of  the  platinum 
wires  on  which  the  cups  travel.  Thus  if  the  resistance  offered 
by  the  rheoehord  when  the  cups  are  quite  at  the  bottom  of  the 


BY   DR.    MICHAEL   FOSTER.  355 

board,  but  all  the  plugs  in  place,  be  taken  as  the  unit,  the  re- 
moval of  the  plug  marked  5  will  suddenly  introduce  in  addi- 
tion five  times  that  amount  of  resistance,  and  so  send  a  pro- 
portionate amount  of  the  current  through  the  circuit  of  the 
electrodes. 

IX.  The  Double  Key  or  Wippe. — This  is  very  con- 
venient when  it  is  desired  to  throw  a  given  current  from  one 
pair  of  electrodes  into  another.  It  is  represented  in  fig.  299, 
in  which  it  is  seen  that  the  mercury  cups  belonging  to  the 
binding  screws  1  and  2  are  connected  by  a  handle  of  which  the 
central  part  is  of  insulating  material,  the  ends  of  thick  copper 
wire.  Each  of  the  copper  wires  is  crossed  just  as  it  enters 
the  handle  by  an  arch  of  the  same  material ;  one  end  of  each 
arch  dips  into  one  of  the  mercury  cups  3  and  4,  when  the 
handle  is  thrown  to  the  right  as  in  the  figure.  The  wires  from 
one  pair  of  electrodes  are  to  be  brought  to  the  binding  screws 
3  and  4,  those  from  the  other  to  the  screws  5  and  6.  The  small 
cups  on  the  surface  are  to  be  filled  with  mercury,  and  the  wires 
from  the  battery  or  induction  coil,  etc.,  brought  to  the  screws 
1  and  2,  and  the  straight  cross  wires  between  3  and  6  and  4 
and  5  taken  awa3r.  By  throwing  the  handle  to  the  right,  the 
current  from  the  battery  is  sent  into  the  wires  connected  with 
the  screws  3  and  4;  by  throwing  the  handle  to  the  left,  into 
the  wire  connected  with  the  screws  5  and  6. 

X.  The  Marking  "Lever. — This  is  a  two-armed,  flat, 
metal  lever,  fig.  275  a  a\  working  vertically  on  the. pivot  6,  the 
arm  a  being  considerably  heavier  than  a'.  The  pivot  is  elec- 
trically continuous  with  the  small  brass  pillar  c,  where  binding 
screws  receive  a  wire  or  wires  from  a  battery,  induction  coil, 
electrode,  etc.  The  pillar  c  is  placed  on  one  side  of  the  sup- 
port d,  made  of  non-conducting  material,  which  by  e  can  be 
clamped  to  any  stand,  either  vertically  or  horizontally.  On 
the  other  side  of  the  support  is  a  similar  pillar/  (also  bearing 
binding-screws),  on  which  the  arm  a  of  the  lever  rests  ;  g  is  a 
weak  spring,  which  serves  to  catch  the  end  of  the  lever  when 
thrown  up  ;  h  is  a  slip  of  gutta-percha  or  India-rubber  at  the 
end  of  the  lever  bearing  the  marking  needle  or  pen. 

If  c  be  connected  with  one  of  the  poles  of  the  battery,  and 
/  with  one  end  of  the  primary  coil,  when  the  lever  is  down  and 
horizontal,  the  arm  a  being  in  close  contact  with  the  pillar,  the 
current  passes  along  the  lever  from  c  to  /.  When,  therefore, 
the  arm  a  of  the  lever  is  suddenly  tilted  up,  which  can  easily 
be  done  with  the  point  of  the  finger,  the  current  is  suddenly 
broken  ;  and  the  moment  of  the  breaking  is  indicated  on  the 
registering  surface  by  the  descent  of  the  marking  point  of  the 
lever.  When  it  is  desired  to  mark  the  making  rather  than  the 
breaking  of  a  current,  the  two  positive  (or  negative)  wires 
must  be  brought  to  the  binding  screws  of/,  and  the  two  nega- 


356  GENERAL    DIRECTIONS. 

tive  (or  positive)  to  those  of  c.  The  tilting  up  of  a  will  then 
correspond  to  the  making  of  a  current  as  in  Du  Bois  Rej- 
inond's  key.     (See  below.) 

XI.  Arrangement  of  Apparatus  for  Experiment. — 
The  electrodes  being  charged  and  fastened  in  their  bearers,  the 
bearers  secured  in  the  clamps,  and  the  wires  from  the  electrodes 
brought  to  the  binding-screws  of  the  platform  of  the  moist- 
chamber,  fasten  the  femur  of  the  nerve-muscle  preparation 
securely  in  the  clamp,  in  such  a  way  that  the  muscle*  hangs 
vertically  downwards  over  the  slit.  Seize  the  vertebral  frag- 
ment with  the  forceps,  and  gently  lodge  the  nerves  on  the 
electrodes.  Firmly  fasten  the  tendo  Achillis  in  a  Kronecker's 
clamp  (fig.  274),  and  with  a  strong  silk  thread  of  appropriate 
length  connect  the  Kronecker  with  the  lever,  the  silk  passing 
through  the  slit.  Adjust  the  arm  bearing  the  muscle,  and  that 
bearing  the  lever,  in  such  a  way  that  the  muscle  hangs  per- 
fectly vertical,  and,  without  being  actually  on  the  stretch,  is  so 
attached  to  the  lever  (which  should  be  in  a  perfectly  horizontal 
position)  that  the  slightest  contraction  of  the  former  will  move 
the  latter. 

Bring  the  wires  from  the  battery,  induction  coil,  etc.,  to  the 
binding-screws  which  carry  the  wires  of  the  electrodes.  Place 
the  glass  shade  over  the  platform,  with  wet  blotting-paper 
inside,  being  careful  that  the  wet  paper  touches  neither  the 
nerve-muscle  nor  the  wires. 

Prepare  weights  for  loading  the  lever;  the  most  convenient 
are  5,  10,  20,  30,  50,  150,  200,  and  300  grammes.  Place  the 
whole  apparatus  so  that  the  point  of  the  lever  touches  the 
registering  surface. 

Where  it  is  required  to  study  the  muscle  without  removing 
it  from  the  circulation,  another  method  must  be  adopted, 
which  may  be  followed  in  other  cases  as  well.  The  upper 
surface  of  the  platform  should  in  this  case  be  provided  with  a 
thick  layer  of  cork. 

Having  pithed  the  frog,  pin  it  firmly,  bell}'  downwards,  on 
the  cork  of  the  platform,  fixing  the  thigh  of  one  side  espe- 
cially tight ;  one  of  the  pins  should  be  passed  close  to  the 
femur,  on  the  anterior  surface  of  the  thigh,  just  above  the 
knee.  Make  a  slight  longitudinal  slit  along  the  tendo  Achillis, 
which  divide  low  down,  and  carefully  dissect  out  for  a  few 
millimetres;  put  a  small  but  strong  S  hook,  with  a  silk  thread 
attached,  in  the  tendon,  pass  the  silk  over  one  of  the  small 
double-cone  pulleys  which  are  fixed  on  to  the  platform,  and  so 
through  the  arms  of  the  T  slit  to  the  lever  below. 

The  sciatic  nerve  may  now  be  dissected  out  in  the  thigh 
without  injuring  the  bloodvessels,  and  the  curved  electrodes 
slipped  beneath  it. 

Where  the  recording  cylinder  used  rotates  on  its  horizontal, 


BY    DR.    MICHAEL    FOSTER.  357 

and  not  on  its  vertical,  axis,  the  simple  lever  must  be  fixed  in 
a  horizontal  position  at  the  front  of  the  platform,  and  the  silk 
brought  in  a  straight  line  to  it  from  the  tendon.  Resistance 
to  the  action  of  the  muscle  may  then  be  gained  by  means  of 
the  light  spring,  or  a  weight  passing  over  another  pulley.  As 
a  rule,  it  is  best,  when  possible,  to  do  without  a  pulle}*-. 

XII.  Recording  Tuning-Fork. — For  measuring  small 
intervals  of  time  in  plrvsiological  observations,  it  becomes 
absolutely  necessary  to  make  use  of  tuning-forks  of  known 
rates  of  vibration.  Fig.  277  is  a  figure  of  a  tuning-fork 
arranged  by  Konig  for  recording  its  vibrations  on  a  revolv- 
ing surface.  A  massive  stand  bears  the  fork  A  firmly  secured 
in  it.  The  two  coils  c  c'  (which  by  means  of  the  arrangement 
k  can  be  slid  up  and  down  the  stand,  so  as  to  accommodate 
themselves  to  tuning-forks  of  different  lengths)  project  over 
the  two  ends  of  the  fork,  and  each  bears  a  screw  d  which  can 
be  screwed  as  desired  up  to  or  away  from  the  ends  of  the  fork. 
The  upper  arm  of  the  fork  bears  at  its  end  a  rod  a  with  plati- 
num point  which  dips  into  the  mercury  cup  b. 

The  tuning-fork  B,  which  must  have  the  same  rate  of  vibra- 
tion as  A,  is  fixed  into  a  light  movable  stand,  so  that  it  can 
be  placed  in  such  a  position  that  the  light  elastic  marker  g 
may  touch  with  the  least  excess  of  friction  the  recording  sur- 
face. This  fork  is  placed  in  the  same  manner  as  A,  with  its 
ends  between  the  coils  e  e',  bearing  similarly  the  screws  f  f. 

One  wire  from  a  battery  w  is  connected  with  a  binding 
screw  at  the  handle  of  the  tuning-fork  A,  and  is  thus  in  electric 
continuity  with  the  rod  a.  The  mercury  cup  b  is  connected  by 
a  wire  z  with  the  coil  e  of  the  fork  B.  The  other  pole  of  the 
battery  is  connected  by  x  with  the  coils  c  c'  of  A,  and  thence 
by  y  with  the  coil  e'  of  B. 

The  screws  d  d,  f  f  being  brought  rather  near  to  their  re- 
spective forks,  place  a  small  quantity  of  mercury  covered  by  a 
little  spirit  in  the  cup  6,  and  having  set  the  fork  A  vibrating  a 
little,  screw  the  rod  a  up  or  down  until  magnetic  interruption 
is  fairly  established.  B  will  then  be  found  vibrating  synchro- 
nously with  A,  and  the  point  g  will  be  found  tracing  curves 
on  the  recording  surface,  the  interval  of  time  corresponding 
to  each  curve  being  determined  by  the  pitch  of  the  fork. 
Screw  the  d  d,  / '/' ',  as  far  away  from  their  respective  forks  as 
can  be  done  without  stopping  the  current  altogether. 

XIII.  Arrangement  of  Electrical  Apparatus. — Con- 
stant Current. — Place  the  nerve  (or  muscle,  when  muscle 
alone  is  the  subject  of  experiment)  on  the  electrodes,  taking 
care  that  the  nerve  is  actually  in  contact  with  each  electrode. 
When  the  non-polarizable  electrodes  are  used,  their  plugs  must 
be  kept  damp  with  the  normal  saline  solution:  avoid  making 


358  GENERAL   DIRECTIONS. 

them  too  wet,  and  especially  do  not  let  a  bridge  of  fluid  form 
along  the  nerve  between  the  two  electrodes. 

Bring  the  wire  from  each  electrode  to  the  outer  binding  screw 
on  each  side  of  a  Du  Bois  Raymond's  key  (fig.  300).  Bring 
the  wires  from  the  battery  to  the  inner  screws  of  the  same  key. 
Let  the  positive  wire,  the  wire  connected  with  the  copper, 
carbon,  platinum,  etc.,  of  the  battery  be  colored  of  some  defi- 
nite color,  e.  g.,  red;  let  the  wire  fastened  to  the  same  side  of 
the  key  have  the  same  color.  The  electrode  connected  with 
this  wire  will  be  the  positive  electrode,  or  anode.  Let  the  two 
other  wires  connecting  the  zinc  of  the  battery  with  the  key, 
and  that  side  of  the  key  with  the  other  electrode  which  there- 
fore becomes  the  negative  electrode  or  kathode,  be  colored  of 
some  other  color,  e.  g.,  blue. 

When  the  key  is  down,  the  brass  plate  offers  such  little  re- 
sistance to  the  passage  of  the  current,  compared  with  that 
offered  by  the  nerve,  etc.,  that  the  whole  current  will  pass 
through  the  bridge  of  the  ke}r,  and  none  through  the  nerve. 

Consequently,  opening  the  key  is  equivalent  to  throwing  a 
current  into  the  nerve ;  shutting  the  key,  to  removing  the  cur- 
rent from  the  nerve ;  during  the  whole  time  that  the  key  is 
open,  the  nerve,  etc.,  is  exposed  to  the  action  of  the  current. 

When  the  kathode  (negative  pole)  is  placed  at  a  point  on  the 
nerve  nearer  the  muscle  than  the  anode  (positive  pole),  the 
current  is  said  to  be  descending ;  when  the  anode  is  the  nearer, 
the  current  is  said  to  be  ascending. 

Single  Induction  Shock. — Connect  each  wire  from  the 
battery  (Fig.  276  B),  a  key  b  intervening,  with  one  of  the  two 
screws  on  the  top  of  the  primary  coil  C.  Connect  the  secondary 
coil  D  with  the  electrodes  E  E',  a  key  a  intervening. 

Whenever  the  key  b  is  opened,  and  the  current  from  the 
battery  allowed  to  pass  from  the  primary  coil,  a  current  is  in- 
duced for  the  instant  in  the  secondary  coil ;  another  current 
is  similarly  induced  in  the  secondary  coil  when  the  same  key 
is  shut;  but  in  the  interval  there  is  no  current  produced  in 
the  secondary  coil  provided  that  the  current  in  the  primary 
coil  be  constant. 

If  the  key  a  is  kept  open  while  the  key  b  is  being  opened  or 
shut,  at  each  opening  or  shutting  of  b  a  single  "induction 
shock"  is  sent  through  the  nerve. 

If  a  be  kept  open  when  b  is  opened,  i.  e.,  when  the  current  is 
allowed  to  pass  into  the  primary  coil  (when  the  current  is 
made),  but  closed  before  b  is  closed  again,  a  "  making  or  closing 
induction  shock"  only  will  be  sent  through  the  nerve. 

If  the  key  a  be  kept  closed  while  b  is  opened,  and  opened 
before  b  is  shut  (and  the  current  in  the  primary  coil  is  broken), 
a  "breaking  or  opening  induction  shock"  only  is  passed  through 
the  nerve. 


BY   DR.    MICHAEL   FOSTER.  359 

In  determining  the  direction  of  the  induction  shock,  it  must 
be  remembered  that,  at  making  the  current  in  the  primary  coil, 
the  current  induced  in  the  secondary  coil  is  opposite  in  direc- 
tion to  that  of  the  primary,  but  that  on  breaking  it,  it  is  in  the 
same  direction. 

Interrupted  Current. — For  ordinary  tetanizing  purposes, 
the  magnetic  interruptor  of  Du  Bois  Reymond's  apparatus  is 
used  (see  Fig.  293).  Connect  the  end  of  the  positive  wire  of 
the  batteiy  with  the  brass  column  g,  and  the  negative  wire 
with  a ;  the  current  then  enters  by  y,  passes  along  the  German 
silver  spring,  which  when  not  in  action  is  in  contact,  by  a  little 
plate  of  platinum  soldered  on  to  its  upper  surface,  with  the 
platinum  point  of  the  screw  f.  From  f  the  current  passes 
through  the  brass  block  e,  with  its  binding  screw  d,  to  the  pri- 
mary  coil  c ;  after  traversing  it,  it  reaches  the  electro-magnet 
6,  and  then  returns  to  the  battery  through  the  binding  screw  a. 
The  anchor  h  is  supported  over  the  electro-magnet  by  the  end 
of  the  German  silver  spring;  the  moment  that  the  current 
passes  through  &,  the  anchor  with  the  spring  is  drawn  down 
so  as  to  break  the  current  at  f.  Thereupon,  the  magnet 
ceasing  to  act,  allows  the  spring  to  return  to  its  former  posi- 
tion. By  sliding  the  secondary  coil  to  a  greater  or  less  dis- 
tance from  the  primary,  the  strength  of  the  induced  current 
can  be  varied  at  will. 

When  it  is  specially  important  to  avoid  unipolar  action,  the 
apparatus  must  be  modified  in  the  manner  recommended  by 
Helmholtz.  With  this  view,  connect  the  column  g  with  the 
binding  screw  d  by  a  side  wire  also  marked  g,  and  heighten 
the  tip  of  the  column  a  by  means  of  the  milled  rim.  This 
arrangement  is  shown  in  Fig.  294.  The  current  enters  as  be- 
fore, but  in  its  course  to  the  primary  coil  it  passes  partly 
through  f  and  partly  through  the  side  wire  g.  When  the  an- 
chor is  drawn  down,  as  seen  in  the  figure,  the  spring  rests 
upon  the  summit  of  a,  so  that  the  current  passes  directly  back, 
as  indicated  by  the  arrow,  to  the  battery.  The  moment  this 
is  the  case,  the  current  through  the  electro-magnet  becomes  so 
feeble  that  it  is  insufficient  to  keep  down  the  anchor,  the  spring 
rising  again  comes  into  contact  with  f,  and  so  on.  The  modi- 
fication of  effect  is  as  follows :  1.  The  induced  currents  are 
weaker,  for  the  variations  of  the  strength  of  the  current  are 
less.  2.  The  intensity  of  the  opening  induction  current,  which 
in  the  ordinary  arrangement  is  much  greater  than  that  of  the 
closing,  is  reduced  so  that  the  two  are  nearly  equal. 

If  it  is  desired  to  allow  the  current  from  the  battery  to  tra- 
verse the  primary  coil  without  passing  the  interruptor,  so  as, 
e.  g.,  to  use  the  apparatus  for  producing  single  opening  or 
closing  induction  shocks,  connect  the  positive  wire  of  the  bat- 
tery with  e,  and  the  negative,  as  before,  with  a. 


360  GENERAL   PROPERTIES   OF    MUSCLE    AT    REST. 

It  is  often  advisable  to  use  a  key  both  between  the  battery 
and  the  induction  coil,  and  between  the  secondary  coil  and  the 
electrodes. 

Current  "with  Definite  Interruptions  by  Means  of 
the  Metronome. — Arrange  as  for  a  single  induction  shock, 
except  that,  in  place  of  the  key  b,  insert  the  electrical  metro- 
nome, an  instrument  which  may  be  described  as  a  key  which 
is  opened  and  closed  by  clock-work  at  regular  intervals  of 
time,  the  length  of  interval  being  varied  at  will.  The  key  a 
may  be  dispensed  with,  as,  unless  a  special  provision  be  made, 
the  shocks  given  will  be  both  opening  and  closing. 

Current  interrupted  by  Means  of  an  Oscillating 
Rod. — Bring  one  wire  straight  from  the  battery  to  the  pri- 
mary coil,  connect  the  other  wire  with  a  slip  of  thin  elastic 
steel  (the  length  will  be  determined  by  the  rapidity  of  inter- 
ruption required),  one  end  of  which  is  made  fast,  while  at  the 
other  a  needle,  at  right  angles  to,  but  in  electrical  continuity 
with,  the  steel  slip,  hangs  over  a  mercury  cup  at  such  a  dis- 
tance, that  when  the  steel  slip  is  at  rest,  the  needle  is  quite 
clear  of  the  mercury,  but  that  when  the  slip  is  made  to  oscil- 
late, with  each  oscillation  the  needle  dips  in  and  out  of  the 
mercuiy.  Connect  the  mercuiy  of  the  cup  with  the  other 
binding  screw  of  the  primary  coil.  At  each  oscillation  of  the 
slip,  the  current  will  accordingly  be  made  and  broken. 


CHAPTER  XX. 
GENERAL  PROPERTIES  OF  MUSCLE  AT  REST. 

I.  Elasticity. — Obs.  I.  Take  a  gastrocnemius,  prepared 
as  directed  in  Chap.  XIX.,  sec.  I.,  except  that  the  nerve  may 
be  neglected  wholly ;  fasten  the  femur  in  the  clamp  of  the 
moist  chamber,  and  attach  the  muscle  to  the  lever,  as  directed 
in  sec.  XI.     Let  the  lever  be  perfectly  horizontal. 

Draw  on  the  recording  surface  a  straight  line,  on  which 
make  a  mark  for  zero,  and  mark  off  abscissas  in  the  proportion 
of  10,  30,  50,  100,  150,  200,  300,  400,  etc. 

Disregarding  the  weight  of  the  lever  (or  of  the  pan,  etc., 
when  Helmholtz's  arrangement  is  used),  the  muscle  may  be 
supposed  to  have  its  natural  length  when  no  weight  is  brought 
to  bear  upon  it.  This  may  be  indicated  by  bringing  the  re- 
cording point  of  the  lever  to  touch  the  zero  point  on  the  re- 
cording surface.  Xext  shift  the  recording  surface  until  the 
point  of  the   lever   touches   the    point  corresponding  to   10. 


BY    DR.    MICHAEL   FOSTER.  361 

Then  place  10  grammes  in  the  pan,  or  hang  a  10  gramme 
weight  on  the  lever.  The  point  of  the  lever  will  move  clown- 
wards,  describing  a  line  of  a  certain  length.  This  indicates 
the  amount  of  extension  which  the  muscle  has  suffered  in  con- 
sequence of  being  loaded  with  the  10  gramme  weight. 

Remove  the  weight  carefully  ;  the  point  of  the  lever  will  re- 
turn to  the  point  where  it  was  before  the  weight  was  applied. 

The  distance  of  the  point  of  attachment  of  the  muscle  and 
that  of  the  point  of  the  lever  from  the  fulcrum  being  known, 
the  actual  extension  of  the  muscle  with  10  grammes  may  be 
calculated  from  the  length  of  the  line  marked  on  the  cylinder. 

"Ifuscle  possesses  very  little  elasticity  (i.  e.,  is  very  extensi- 
ble) ;  but  that  little  is  very  perfect ;  i.  e.,  on  withdraival  of  the 
extending  force,  the  muscle  returns  very  rapidly  and  com- 
pletely to  Us  previous  length.''1 

Obs.  II.  Now  move  the  recording  surface  till  the  lever  point 
stands  at  the  mark  30;  load  the  pan  with  30,  and  proceed  as 
before.  Repeat  at  50, 100,  200,  etc.  Before  trying  the  heavier 
weights  (300,  400),  see  that  everything  is  secure,  especially  the 
clamps  on  the  femur  and  on  the  tendon.  As  a  general  rule, 
the  attachment  of  the  muscle  to  the  femur  at  last  gives  way. 

With  the  heavier  weights  it  will  be  found  that  the  muscle 
returns  after  extra  extension  and  upon  removal  of  the  weights 
towards  its  former  length,  at  first  very  quickly,  and  then  more 
and  more  slowly — and  that  even  after  waiting  for  some  minutes, 
it  does  not  regain  its  former  length  completely. 

This  falling  short  of  a  complete  return  is  due  to  exhaustion 
(commencing  death,  see  Obs.  IV.).  The  student  had  better, 
in  one  set  of  observations,  start  in  each  case  from  the  point  of 
the  ordinate  to  which  the  lever  had  returned  after  the  previous 
extension,  but  of  course  from  the  next  point  on  the  abscissa, 
and  in  another  set  bring  down  the  recording  surface  in  each 
case  so  that  the  lever  may  start  afresh  from  the  abscissa  line. 
The  lever  should  be  horizontal  at  the  beginning  of  each  trial. 
The  pan  or  weight  should  also  be  allowed  to  descend  very 
gradually  and  slowly,  to  avoid  momentum.  Where  there  is 
no  arrangement  for  keeping  the  recording  point  in  a  straight 
line,  a  horizontal  line  drawn  through  the  end  of  each  curve  will 
cut  off  from  a  vertical  line,  drawn  through  the  starting-point, 
a  line  equal  to  the  vertical  distance  traversed  by  the  lever 
point. 

If  now  the  lines  so  obtained  be  examined,  it  will  be  found 
that  though  with  the  greater  weights  there  is  greater  extension, 
yet  the  increase  of  extension  caused  by  increase  of  weight  gets 
less  and  less.  The  extension  increases  not  in  direct  propor- 
tion to  the  weight,  but  with  continually  diminishing  increments. 
If  a  line  be  drawn  through  the  points  which  in  each  case  mark 
the  limit  of  extension,  that  line  will  not  be  a  straight  line  as  it 


3G2  GENERAL    PROPERTIES   OF   MUSCLE   AT    REST. 

would  he  if  the  extension  were  in  direct  proportion  to  the 
weight,  but  will  he  a  curve,  sinking  very  rapidly  at  first,  hut 
afterwards  more  and  more  slowly,  and  so  continually  tending 
to  run  parallel  to  the  ahscissa  line ;  in  fact,  it  will  he  an  hyper- 
bola. 

Obs.  III.  Neither  of  the  ahove  set  of  observations  is  quite 
correct :  to  eliminate  the  effects  of  exhaustion,  the  observations 
should  he  repeated  on  the  muscle  within  the  body  (see  Chap. 
XIX.,  sec.  XL),  and  time  allowed  between  each  observation 
for  the  muscle  completely  to  recover  itself. 

Obs.  IV.  Kill  the  muscle  (either  the  same  or  a  fresh  one)  by 
immersing  it  in  water  at  40°  C.  for  five  minutes. 

Repeat  Obs.  I.  and  II.  on  the  muscle  so  killed.  It  will  be 
found  that  there  is  far  less  extension  of  the  muscle,  which,  after 
the  load  has  been  removed,  does  not  return  to  its  original 
length. 

The  dead  muscle,  as  compared  with  the  living  one,  is  more 
elastic,  i.  e.,  is  less  extensible ;  but  its  elasticity  is  very  imper- 
fect, i.  e.,  the  original  length  is  not  regained. 

II.  Reaction. — Obs.  V.  Having  pithed  a  frog,  place  a  ca- 
nula  in  the  aorta,  slit  open  the  right  auricle,  and  drive  all  the 
blood  out  by  injecting  the  normal  saline  solution,  which  should 
be  perfectly  neutral.  Dissect  out  the  gastrocnemius  of  one 
side  with  clean  instruments,  and  with  a  very  clean  knife  cut  it 
across  through  the  middle  of  its  belly.  Take  two  slips  of  lit- 
mus paper,  one  faintly  red,  the  other  faintly  blue ;  press  the 
cut  end  of  one-half  of  the  muscle  on  one  piece,  and  the  other  on 
the  other.  On  the  red  litmus  paper  will  be  left  a  distinct  blue 
mark  where  the  muscle  was  pressed  ;  on  the  blue  litmus  paper 
there  will  be  no  mark  at  all,  or,  if  any,  a  change  in  the  direc- 
tion of  red,  which  is  distinctly  less  red  than  the  blue  mark  on 
the  red  litmus  is  blue. 

The  reaction  of  living  muscle,  freed  as  much  as  possible  from 
blood,  is  faintly  alkaline. 

Obs.  VI.  Kill  the  corresponding  muscle  in  the  other  leg  by 
immersion  in  water  at  40°  C.  Test  as  in  06s.  V.  The  blue 
litmus  paper  will  be  marked  most  distinctly  red  ;  the  red  not 
altered.  For  this  a  much  stronger  blue  paper  may  he  used. 
The  reaction  is  permanent,  and  therefore  is  not  due  to  carbonic 
acid. 

Muscle,  in  dying,  on  entering  into  rigor  mortis,  becomes  dis- 
tinctly acid. 

Obs.  VII.  Keep  any  of  the  above  rigid  muscles  covered  in  a 
damp  warm  place.  Test  the  reaction  from  time  to  time.  The 
acid  reaction  gives  way  to  an  alkaline  one,  which  increases 
rapidly  in  intensity,  and  soon  far  exceeds  the  natural  alkaline 
reaction.  This  secondary  alkalinity  arises  from  decomposi- 
tion. 


BY    DR.    MICHAEL    FOSTER.  363 

At  the  same  time  the  muscle  will  be  found  to  have  become 
very  extensible,  with  scarcely  any  elasticity. 

06s.  VIII.  Divide  a  fresh  muscle  in  two.  Immerse  for  a 
few  minutes  one  half  (A)  in  water  at  40°  C. ;  the  other  (B)  in 
boiling  water.     Test  the  reaction  of  both. 

A  will  be  acid,  from  development  of  rigor  mortis. 

B  will  be  alkaline.  Before  rigor  mortis  had  time  to  set  in, 
the  albumin  of  the  muscle  was  coagulated.  This  coagulation 
set  free  a  quantity  of  alkali  (see  Chap.  XXXV.) ;  hence  its  re- 
action. 

III.  Transparency. — Obs.  IX.  Take  from  a  frog  a  portion 
of  any  one  of  its  thin  flat  muscles.  The  mylohyoid  is  the  most 
convenient,  but  the  sartorius  (fig.  278  s.),  or  any  other  thin 
muscle,  will  do  as  well.  The  muscle  must  be  perfectly  fresh 
and  irritable,  and  care  must  be  taken  that  at  least  the  middle 
portion  of  muscle  is  not  in  the  least  injured.  Place  the  muscle 
in  normal  saline  solution,  or  serum,  on  the  unheated  "  warm 
stage,"  and  examine  with  a  quarter-inch  object-glass. 

Focus  down  through  the  middle  (least  injured)  portion  of 
the  muscle,  upon  some  object  (bloodvessel,  etc.)  underneath 
the  fibres.  The  distinctness  with  which  this  object  is  seen  will 
be  a  measure  of  the  transparency  of  the  muscular  tissue. 

Keeping  the  eye  fixed  upon  the  above-mentioned  object,  heat 
the  stage.  It  will  be  found  that  when  the  temperature  of  the 
muscle  has  risen  to  40°  C.  (or  a  little  below),  the  object  is  no 
longer  so  distinct  as  before,  or  has  even  become  totally  invisi- 
ble. 

On  entering  into  rigor  mortis,  the  muscular  fibre  becomes 
opaque. 

Living  muscle  is  very  extensible,  with  perfect  elasticity,  of 
alkaline  reaction,  and  considerable  transparency.  On  enter- 
ing into  rigor  mortis  it  loses  its  extensibility,  its  elastieitjr 
becomes  imperfect,  its  reaction  acid,  and  its  transparency 
gives  place  to  opacity. 


864  STIMULATION   OF   NERVE    AND    MUSCLE. 


CHAPTER  XXI. 

PRELIMINARY    OBSERVATIONS    ON    THE    STIMULATION 
OF  NERVE  AND  MUSCLE. 

I.  Electrical  Stimulation. — Obs.  I.  Get  reacty  a  nerve- 
muscle  preparation  and  place  the  nerve  on  a  pair  of  common 
electrodes  ;  or  simply  lay  bare  the  sciatic  nerve,  slip  the  elec- 
trodes underneath,  and  watch  the  leg  for  any  movements  indi- 
cating muscular  contractions.  Connect  the  electrodes  with  a 
battery  of  one,  two,  or  three  cells,  a  key  intervening.  Open 
the  key,  and  after  a  few  seconds  shut  it  again  ;  this  is  equiva- 
lent to  making  and  then  breaking  a  current  in  the  nerve.  It 
will  be  found  that  either  at  the  breaking  or  at  the  making,  or 
at  both  making  and  breaking  of  the  current,  a  single  muscular 
contraction  is  produced  ;  but  that  during  the  passage  of  the 
current  (provided  the  intensity  be  uniform)  there  is  no  con- 
traction at  all. 

Obs.  II.  Instead  of  a  constant  current,  employ  a  single 
induction  shock.  Each  application  of  a  single  induction 
shock  (if  strong  enough),  whether  it  be  an  opening  shock  or  a 
closing  shock,  will  produce  a  single  muscular  contraction. 

Obs.  III.  Instead  of  a  single  induction  shock,  employ  a 
series  of  shocks  rapidly  following  each  other.  These  produce 
a  continued  contraction,  a  tetanus,  which  lasts  during  the 
whole  time  of  the  application  of  the  currents,  or  until  the 
muscle  is  completely  exhausted.  For  this  purpose  use  the 
apparatus  of  Du  Bois  Reymond. 

Obs.  IV.  Lay  bare  the  gastrocnemius  or  any  other  muscle, 
apply  the  electrodes  directly  to  the  muscle  instead  of  to  the 
nerve,  and  repeat  the  above  observations.  The  results  will  be 
the  same. 

II.  Mechanical  Stimulation. — Obs.  V.  Pinch  the  nerve 
sharply  with  a  pair  of  forceps,  prick  the  muscle  with  a  needle ; 
in  either  case  a  contraction  will  take  place. 

III.  Thermal  Stimulation.— Obs.  VI.  Touch  lightly 
either  nerve  or  muscle  with  a  hot  needle  ;  a  contraction  will 
follow. 

IV.  Chemical  Stimulation. — Obs.  VII.  Dip  the  end  of 
the  nerve  into  a  strong  solution  of  common  salt ;  after  a  little 
while  a  series  of  contractions  running  into  tetanus  will  be  ob- 
served in  the  muscles  supplied  by  the  nerve. 

Obs.  VIII.  Kill  the  muscle  and  nerve  by  immersion  for  a 
few  minutes  in  water  at  40°.  The  above  stimuli  applied  to 
either  muscle  or  nerve  will  produce  no  contraction. 


BY    DR.    MICHAEL    FOSTER.  365 


CHAPTER  XXII. 
PHENOMENA  AND  LAWS  OP  MUSCULAR  CONTRACTION. 

I.  The  Muscle  Curve.' — In  order  to  study  the  muscle 
curve,  the  recording  surface  must  travel  with  sufficient 
rapidity.  (The  chief  features  of  the  curve  may  be  seen  when 
Secretan's  cylinder  with  Foucault's  regulator  revolves  on  the 
second  axis.) 

Obs.  I.  Arrange  a  muscle  preparation  in  the  moist  chamber. 
The  electrodes  should  be  placed  at  some  little  distance  from 
each  other  on  the  muscle  itself;  the  nerve  consequently  need 
not  be  prepared.  Load  with  10  or  15  grms.  Underneath  the 
point  of  the  lever  bring  the  recording  tuning-fork  to  bear  on 
the  cylinder. 

Arrange  for  a  single  opening  induction  shock,  but  instead 
of  the  ke}'  b  (Chap.  XIX.,  sec.  XIII.),  insert  the  marking  kej', 
simply  introducing  it  into  one  wire  from  the  batteiy,  so  that 
when  the  lever  is  down  the  current  passes,  but  when  it  is 
raised  (and  the  point  depressed)  the  current  is  broken  (Chap. 
XIX.,  sec.  X.).  The  point  of  the  marking  key  must  be 
brought  close  under  the  recording  point  of  the  lever  but 
above  the  recording  point  of  the  tuning-fork.  Place  all  three 
recording  points  very  carefully  in  the  same  vertical  line. 

The  marking  key  being  closed,  and  the  tuning-fork  vibrat- 
ing, open  the  key  a,  and  remove  the  break  from  the  governor 
of  the  clock-work ,  when  the  cylinder  is  approaching  the  end 
of  the  first  revolution,  open  the  marking  key,  and  as  soon  as 
possible  afterwards  stop  the  cylinder. 

On  the  cylinder  there  will  now  be  seen  three  lines  of  mark- 
ing (see  fig.  279)  ;  a  is  the  line  of  the  marking  key,  and  the 
point  where  it  descends  indicates  the  moment  at  which  the 
current  broke  into  the  muscle  ;  b  is  the  line  of  the  tuning-fork, 
and  each  complete  curve  denotes  a  certain  fraction  of  a  second 
(determined  by  the  pitch  of  the  tuning-fork) ;  c  is  the  line  of 
the  muscle-lever,  m1  marks  the  moment  of  the  beginning  of 
the  contraction,  m2  the  curve's  highest  point,  m?  its  termina- 
tion. Draw  a  straight  vertical  line  m  through  the  point  where 
the  line  a  descends,  and  similar  vertical  (parallel)  lines  m,  m1, 
ra2,  m3,  cutting  a  b  and  c. 

m — m1  will  give  by  measurement  off  b  the  duration  of  the 
latent  period  m1 — m9,  of  the  rise ;  m2 — ms,  of  the  fall ;  and  m1 
— m',  of  the  total  contraction. 


306  LAWS   OF   MUSCULAR   CONTRACTION. 

The  rapidity  of  Se"cretan's  second  axis  is  hardly  sufficient 
to  bring  out  the  latent  period  with  sufficient  distinctness;  but 
the  other  characters  of  the  curve  may  be  very  well  shown. 

The  third,  swiftest,  axis  may  be  used,  but  there  are  diffi- 
culties in  managing  it.  Care  must  be  taken  to  reduce  the 
friction  of  the  various  recording  points  to  a  minimum;  and 
the  observation  should  not  be  taken  till  towards  the  end  of 
the  second  revolution.  Before  that,  the  cylinder  is  far  from 
reaching  its  maximum  (uniform)  speed  ;  after  that,  the  over- 
lapping curves  of  the  tuning-fork  are  difficult  to  decipher. 

Better  results  are  obtained  if  the  cylinder  be  used  horizon- 
tally (the  natural  position  of  the  apparatus)  instead  of  verti- 
cally. The  lever  tuning-fork  and  marking  key  will  of  course 
have  to  be  arranged  accordingly. 

When  the  heavier  mj'ographion  lever  is  emplo3red,  the  effect 
of  the  inertia  of  the  lever  will  make  itself  manifest  in  a  secon- 
dary curve,  at  the  end  of  the  muscle  curve. 

(For  more  exact  observations  than  are  furnished  by  Fou- 
cault's  second  axis,  it  is  better  to  employ  the  pendulum  myo- 
graphion,  see  Wundt  Mechanik  der  Xerveu,  p.  6.) 

A  muscular  contraction,  even  when  produced  by  an  instan- 
taneous electric  shock,  takes  a  measurable  time  for  its  com- 
plete development.  The  contraction  does  not  begin  at  the 
moment  when  the  stimulus  breaks  into  the  muscle,  but  is  pre- 
ceded by  a  latent  period.  The  contraction  curve  rises  at  first 
very  rapidly,  but  afterwards  more  slowly,  and  having  reached 
a  maximum,  declines  at  first  slowly,  afterwards  more  rapidly, 
and  lastly  more  slowly  again. 

The  advanced  student  may  determine  by  the  same  method 
the  variations  in  the  character  of  the  muscle  curve,  caused 
by:- 

1.  Exhaustion. — Obs.  II.  Having  determined  with  a  single 
induction  shock  the  natural  curve,  exhaust  the  muscle  b}r  pro- 
longed or  repeated  stimulation  with  the  interrupted  current, 
and  then  repeat  again  with  the  same  single  induction  shock  as 
before.  The  curve  will  be  not  only  of  less  height,  but  will  be 
longer,  i.e.,  the  contraction  will  be  slower,  and  the  latent  period 
especially  will  be  prolonged. 

2.  Heat  and  Cold. — Obs.  III.  The  temperature  of  the 
chamber  may  be  raised  or  lowered  by  introducing  a  current 
of  moist  hot  air  or  pieces  of  ice  into  it. 

It  is  more  convenient,  however,  to  use  the  frog  in  a  hori- 
zontal position,  simply  laying  bare  the  gastrocnemius,  and 
dividing  its  tendon  (see  Chap.  XIX.,  sec.  XI.),  and  then 
placing  the  muscle  in  a  double  trough,  made  by  bending  a 
piece  of  leaden  tube.  Having  determined  the  natural  curve, 
pass  hot  or  ice-cold  water  through  the  tube,  and  determine  the 
curve  at  various  temperatures. 


BY   DR.    MICHAEL   FOSTER.  367 

At  higher  temperatures  than  the  normal,  the  muscle  curve 
is  much  shortened  ;  at  lower,  lengthened. 

3.  Poisons  :  Veratrin,  etc. — 06s.  IV.  Arrange  the  frog 
as  directed  for  observations  on  muscles  in  the  living  body 
(Chap.  XIX.,  sec.  XI),  and  having  determined  the  natural 
muscle  curve,  inject  a  small  quantity  of  veratrin  (^V-sV  mgrm.) 
beneath  the  skin  of  the  back,  having  previously  divided  the 
sciatic  nerve  near  the  knee  without  injury  to  the  bloodvessels. 
Determine  the  curve  at  given  intervals  after  the  introduction 
of  the  poison;  the  duration  of  the  contraction  will  be  enor- 
mously prolonged. 

II.  The  Contraction  as  a  Function  of  the  Stimulus. 

Obs.  V.  Arrange  the  nerve  muscle  preparation  in  the  moist 
chamber ;  place  the  nerve  over  a  pair  of  electrodes.  Load  the 
muscle  with  about  10  grammes.  Arrange  for  a  single  induc- 
tion shock,  using  in  the  same  series  of  observations  the  same 
either  opening  or  closing  shock.  Draw  an  abscissa  line  on  the 
recording  surface. 

Slide  the  secondary  coil  as  far  away  as  the  sliding  board 
will  allow  from  the  primary  coil.  Send  a  shock  through  the 
nerve.  If  there  is  no  contraction  (and  most  probably  there 
will  be  none),  move  the  secondary  coil  some  centimetres  nearer 
the  primary;  repeat  the  shock.  Advance  in  this  way,  gradu- 
ally bringing  the  secondary  coil  nearer  and  nearer  to  the  pri- 
mary, until  the  first  visible  contraction  is  gained. 

By  sliding  the  secondary  coil  backwards  and  forwards, 
accurately  determine  this  "minimum  stimulus"  for  the  muscle 
and  nerve  under  the  circumstances  of  the  case. 

Advance  now  steadily  on,  moving  the  secondary  coil  a 
definite  distance  nearer  the  primary  each  time,  and  record 
each  contraction  as  an  ordinate  on  the  abscissa  line,  at  dis- 
tances proportionate  to  the  distances  the  secondary  coil  is 
moved,  in  a  manner  similar  to  Chap.  XX.,  Obs.  II. 

The  contractions  will  go  on  for  a  while  increasing  as  the 
strength  of  the  current  increases;  but  at  last  it  will  be  found 
that  increasing  the  stimulus  no  longer  increases  the  contrac- 
tion, i.  e.,  the  ''maximum  contraction"  for  the  muscle  and 
nerve  under  the  circumstances  has  been  reached.  Determine 
accurately  the  relative  positions  of  the  two  coils  at  which  this 
point  is  reached. 

If  with  the  battery  employed  to  start  with  the  maximum 
contraction  is  not  reached,  increase  the  number  of  cells. 

The  student  in  making  the  above  observations  is  nearly  sure 
to  meet  with  very  great  irregularities,  which  will  tend  very 
much  to  confuse  the  results.  These  may  be  partly  due  to 
imperfections  in  the  apparatus.  He  will  therefore  carefully 
examine  these,  and  see  that  everything  is  in  order,  and  espe- 
cially that  the  battery  is  working  steadily. 


3G8         LAWS  OF  MUSCULAR  CONTRACTION. 

But  the  variations  will  in  most  cases  be  due  to  the  fact  that 
the  nerve  after  stimulation,  and  the  muscle  after  stimulation 
and  contraction,  are  for  a  variable  period  of  time  in  a  different 
condition  from  what  they  were  before.  They  are  suffering 
from  more  or  less  exhaustion,  reaction,  etc.  To  eliminate 
these  entirely  is  a  task  of  considerable  difficulty.  They  may 
be  more  or  less  reduced  by  waiting  a  sufficiently  long  time 
between  each  two  trials,  by  working  backwards  from  the 
stronger  shocks  to  the  weaker,  as  well  as  from  the  weaker  to 
the  stronger,  etc.  etc. 

The  student,  however,  will  see  sufficient  to  enable  him  to 
state  that  the  amount  of  contraction  does  increase  with  the 
increase  of  the  strength  of  the  shock  {increase  of  stimulus), 
at  first  rapidly,  then  more  and  more  slowly,  and  finally,  when 
the  maximum  is  reached,  ceasing  to  increase  any  more. 

III.  The  Contraction  as  a  Function  of  the  Resist- 
ance. 

Obs.  VI.  Everything  being  arranged  as  in  the  last  observa- 
tion, place  the  secondary  coil  in  such  a  position  as  to  give  a 
shock  about  midway  between  the  maximum  and  minimum 
stimulus. 

"  First  let  there  be  no  load  to  the  muscle ;  record  the  contrac- 
tion as  an  ordinate  on  the  abscissa  line.  Then  load  succes- 
sively with  10,  30,  50,  100,  etc.  etc.,  grammes;  recording  the 
several  contractions  at  proportionate  distances  along  the  ab- 
scissa line. 

Repeat  with  a  minimum  stimulus  and  also  with  a  maximum 
stimulus. 

With  the  same  stimulus  the  amount  of  contraction  decreases 
as  the  load  is  increased ;  but  not  regularly.  At  first,  as  the 
load  is  increased  from  zero  upwards  by  small  increments,  the 
contraction  increases;  as  the  load  continues  to  be  increased, 
the  increment  diminishes,  and  finally  gives  place  to  a  decre- 
ment. The  initial  increase  of  contraction  is  most  prominent 
when  the  stimulus  lies  within  a  certain  range  of  intensity. 

IV.  The  Work  Done. 

06s.  VII.  The  dimensions  of  the  lever  being  known,  deter- 
mine from  the  ordinates  of  contraction  the  actual  shortening 
of  the  muscle  itself  during  each  contraction.  This  multiplied 
into  the  weight  will  give  the  ivork  done  in  each  case. 

Draw  an  abscissa  line  and  mark  off  from  it  distances  propor- 
tionate to  the  loads  employed  in  Obs.  VI.  Draw  as  ordinates 
the  actual  work  done  in  the  case  of  each  load.  A  line  drawn 
through  the  summits  of  the  ordinates  will  give  the  curve  of 
the  icork  done  with  the  same  stimulus  and  increasing  loads. 

With  the  same  given  stimulus  and  an  increasing  load,  the 
work  done  increases  up  to  a  maximum,  and  then  declines. 


BY    DR.    MICHAEL    FOSTER.  369 

The  maximum  is  not  the  same  with  all  intensities  of  stimulus. 

There  is  a  definite  relation  of  load,  muscle,  and  stimulus, 
by  which  the  greatest  amount  of  work  can  be  got  out  of  a 
given  muscle. 


CHAPTER   XXIII. 
THE  WAVE  OF  MUSCULAR  CONTRACTION. 

Obs.  I.  Place  a  nerve-muscle  preparation  in  a  horizontal 
position,  so  that  the  gastrocnemius  rests  on  some  flat  surface 
(e.  g.,  a  glass  plate)  over  which  it  can  glide  freely  ;  clamp  the 
femur  fragment  tight ;  b}r  means  of  a  pulley  attach  the  tendon 
to  a  lever,  etc.,  with  a  load  of  10  or  15  grammes.  Bring  over 
the  middle  of  the  muscle  the  button  of  a  light  cardiograph 
connected  with  a  Marey's  tambour  (see  p.  265,  fig.  230).  If 
the  button  is  large,  attach  to  its  under  surface  a  conical  piece 
of  cork  or  some  other  material,  which  can  be  brought  into 
contact  with  a  small  portion  of  the  surface  of  the  muscle. 

Bring  the  recording  point  of  the  tambour  lever  to  mark  on 
the  cylinder,  a  little  distance  below  the  other  lever. 

Place  the  nerve  on  the  electrodes  of  an  induction  coil. 

While  the  cylinder  (first  or  second  axis)  is  revolving,  and 
the  two  levers  are  describing  parallel  lines,  send  induction 
shocks  of  various  strengths  through  the  electrodes. 

The  direct  lever  will  indicate  the  shortening  of  the  muscle, 
the  tambour  lever  its  thickening.  It  will  be  seen  that  they 
both  take  place  at  about  the  same  time,  and  that  with  the 
various  strengths  of  current  the  movement  of  one  lever  in- 
creases or  decreases  with  the  other. 

06s.  II.  Poison  a  frog  completely  with  urari,  so  as  to  eli- 
minate as  much  as  possible  the  influence  of  nerves.  Dissect 
out  carefully  one  of  the  large  muscles  of  the  thigh  ;  for  in- 
stance, the  rectus  interims  major  (fig.  278,  r.  i).  Cut  away 
with  it  the  piece  of  the  pelvis,  to  which  its  origin  is  attached. 
Leave  as  much  of  the  tendon  of  insertion  as  possible. 

Lay  the  muscle  in  a  small  trough  (fig.  280)  (one  can  easily 
be  made  of  gutta-percha),  and  place  over  it,  as  far  apart  as 
possible,  two  levers.  The  levers  must  be  so  arranged  that 
their  points  write  on  the  cylinder  one  below  the  other  in  ex- 
actly the  same  vertical  line.  Fix  the  one  end  of  the  muscle 
1)}'  clamping  the  piece  of  pelvis,  and  attach  by  means  of  a 
pulley  a  load  of  5  or  10  grammes  to  the  tendon. 

Bring  two  pointed  electrodes  from  an  induction  coil,  to  one 
24 


370  THE    WAVE    OF   MUSCULAR    CONTRACTION. 

end  of  the  muscle,  so  that  they  touch  the  muscular  fibres  close 
to  the  end. 

Bring  the  levers  to  trace  on  the  cylinder  rotating  on  its 
swiftest  axis.  While  the  two  points  of  the  lever  are  describ- 
ing two  parallel  lines  on  the  cylinder,  send  a  single  induction 
shock  through  the  lever. 

Each  of  the  two  levers  will  describe  a  curve,  each  curve  in- 
dicating the  thickening  of  the  muscle  under  the  lever  during 
the  contraction.  But  these  curves  will  not  be  exactly  one 
under  the  other ;  one,  viz.,  that  described  by  the  lever  nearer 
the  electrodes,  will  be  a  little  earlier  than  the  other.  The  dif- 
ference in  time  between  the  commencement  of  the  two  curves 
will  be  more  marked  in  an  exhausted  muscle,  or  in  a  muscle 
exposed  to  a  low  temperature,  than  in  a  fresh  and  very  irri- 
table muscle. 

The  contraction  then  does  not  take  place  in  the  vihole  fibre 
at  the  same  time,  but  travels  with  a  certain  velocity  from  the 
point  at  which  the  electrodes  are  placed  along  the  fibre. 

Obs.  III.  Repeat  the  observation  ;  placing  the  electrodes  on 
the  muscle  close  to  the  tendon  of  insertion  instead  of  close  to 
the  origin. 

The  results  are  just  the  same;  the  wave  of  contraction 
travels  in  either  direction. 

Obs.  IV.  Instead  of  resting  the  levers  on  the  muscle  as  di- 
rected above,  the  muscle  may  be  placed  on  a  piece  of  cork 
with  holes  in  it  and  two  slips  of  thin  foil  looped  round  two 
distant  parts  of  the  muscle,  each  slip  being  connected  with  a 
lever  below,  as  in  fig.  281. 

If  the  tuning-fork  be  brought  to  trace  on  the  cjdinder  be- 
low the  levers,  the  interval  of  time  between  the  commence- 
ments of  the  two  contractions  may  be  exactly  determined, 
and  the  distance  between  the  two  levers  on  the  muscle  bein«: 
accurately  measured,  the  velocity  of  the  wave  of  contraction 
mav  be  calculated. 


BY   DR.    MICHAEL   FOSTER.  371 


CHAPTER  XXIV. 
TETANUS. 

1.  The  Curve  of  Tetanus. — 06s.  I.  Having  arranged 
the  nerve-muscle  preparation,  etc.,  in  the  moist  chamber  as 
usual,  draw  first,  if  not  read}7  at  hand,  the  curve  of  a  simple 
muscular  contraction,  for  comparison. 

Then  connect  the  electrodes  with  the  induction  machine 
using  the  magnetic  interruptor ;  insert  between  the  secondary 
coil  and  the  electrodes  the  marking  key  with  double  circuit; 
raising  the  marking  key  will  now  allow  an  interrupted  current 
to  fall  into  the  nerve ;  on  pressing  the  key  down  the  current 
will  be  shut  off. 

All  being  arranged  (the  slow  axis  of  Secretan's  instrument 
will  give  sufficient  speed),  allow  an  interrupted  current  of 
very  moderate  intensity  (i.  e.,  the  secondary  coil  hardly,  if  at 
all,  overlapping  the  primary  with  a  weak  battery)  to  break 
into  the  nerve,  and  in  a  few  seconds  shut  it  off  again. 

A  curve  similar  to  that  shown  in  fig.  282  will  be  obtained  ; 
where  the  plumb  line  m  drawn  through  the  first  a  marks  the 
commencement  both  of  the  stimulation  and  contraction  (the 
speed  not  being  sufficient  to  show  the  latent  period),  and  the 
line  m2  through  the  second  a  marks  the  end  of  the  stimulation, 
and  m3  the  end  of  the  contraction. 

It  will  be  seen  that  the  curve  rises  at  first  very  rapidly,' 
afterwards  more  slowly,  and  speedily  reaches  a  maximum,  which 
it  maintains  during  the  whole  time  of  the  stimulation.  Upon 
the  cessation  of  the  stimulus  at  m2,  the  curve  at  once  falls,  at 
first  very  rapidly,  but  afterwards  more  slowly,  and  in  its  later 
phases  very  slowly. 

If  the  stimulus  is  allowed  to  act  upon  the  muscle  for  more 
than  a  few  seconds,  the  curve  begins  to  decline,  even  while  the 
stimulus  is  still  acting  ;  but,  even  after  very  prolonged  stimu- 
lation, the  cessation  of  the  stimulus  is  indicated  by  a  sharp 
fall  in  the  curve. 

Tetanus  from  an  ordinary  interrupted  current  is  a  continued 
contraction  rapidly  reaching  a  maximum,  continuing  (within 
limits)  in  that  condition  so  long  as  the  current  is  passing,  and 
followed  by  a  gradual  relaxation  upon  the  current  being  cut 
of. 

1  In  the  figure  the  curve  does  not  rise  rapidly  enough. 


372  TETANUS. 

Obs.  II.  Arrange  for  a  single  induction  coil,  hut  replace  the 
key  b  by  the  oscillating  interruptor  (Chap.  XIX.,  sec.  XI 11.). 
Use  the  first  or  the  second  axis  of  Secretan,  and  the  needle  of 
the  interruptor  being  clear  of  the  mercury,  open  the  key  a, 
and  set  the  cylinder  revolving.  When  uniformity  of  speed 
has  been  reached,  suddenly  set  the  interruptor  vibrating,  and 
after  some  ten  vibrations  or  so  have  taken  place,  close  the  key  a. 

The  tracing  on  the  cylinder  will  be  a  curve  of  the  character 
shown  in  fig.  283. 

In  general  features  it  resembles  the  curve,  fig.  282.  There 
is  the  same  rise,  maximum,  and  fall ;  but  instead  of  being,  as 
in  fig.  282,  apparently  a  simple  curve,  it  is  evidently  composed 
of  a  series  of  curves.  Each  of  these  component  curves  cor- 
responds to  a  contraction  caused  by  a  breaking  or  a  making 
of  the  primary  current  through  the  needle  dipping  into  or 
coming  out  of  the  mercury.  It  will  be  seen  that  the  second 
contraction  began  before  the  first  was  completed,  and  is,  so  to 
speak,  placed  on  the  top  of  it;  in  the  same  way,  the  third 
comes  on  the  top  of  the  second,  and  so  on.  The  amount  of 
rise  contributed  by  each  subordinate  curve  to  the  total  rise  is 
greatest  in  the  first,  and  goes  on  diminishing  until  the  maxi- 
mum is  reached. 

By  varying  the  length  of  the  oscillating  slip,  a  series  of 
curves  may  be  obtained,  showing  the  various  steps  between  a 
series  of  quite  separate  contractions,  each  being  completed 
before  the  next  begins,  and  one  in  which  (as  in  the  tetanus 
produced  with  the  magnetic  interruptor)  the  individual  con- 
tractions follow  each  other  so  rapidly,  that  no  trace  of  their 
separate  existence  is  visible  on  the  recording  surface. 

Tetanus  really  consists  of  a  series  of  simple  muscular  con- 
tractions fused  together. 

II.  The  Effects  of  Exhaustion. 

Obs.  III.  Throw  a  muscle,  with  the  electrodes  applied  to  the 
muscle  itself,  into  tetanus,  with  a  strong  interrupted  current. 
Record  the  movement  on  the  cylinder.  Continue  the  current 
for  some  minutes.  The  curve  will  gradually  fall  from  the  maxi- 
mum down  to  very  nearly  the  abscissa  line ;  but  even  after 
very  prolonged  action,  a  sudden  fall  will  mark  the  shutting  off 
the  current. 

Obs.  IV.  Send  through  a  muscle  a  single  induction  shock  of 
a  certain  strength.  Record  the  contraction.  Then  tetanize 
the  muscle  by  means  of  the  interrupted  current  for  ten  or 
twenty  seconds.  Apply  again  the  same  induction  shock  as 
before.  There  will  be  either  a  much  slighter  contraction  than 
before,  or  none  at  all.  After  waiting  some  minutes,  repeat  the 
shock  again.  The  contraction  will  now  be  much  nearer  its 
former  dimensions. 


BY    DR.    MICHAEL    FOSTER.  373 

By  contraction,  especially  hy  tetanus,  irritability  of  a  muscle 
is  diminished;  after  a  period  of  rest,  the  irritability  returns 
even  in  a  muscle  removed  from  the  blood  current. 

Obs.  V.  Repeat  the  observation  on  a  muscle  still  connected 
with  the  blood  current.  The  return  of  irritability  will  be  much 
more  rapid  and  complete. 

With  a  Du  Bois  Reymond's  induction  apparatus,  the  transit 
tion  from  a  single  induction  shock  to  an  interrupted  current 
may  easily  be  effected  thus  :  The  apparatus  being  arranged  for 
an  interrupted  current,  the  key  a  being  open,  press  the  spring 
of  the  magnetic  interruptor  up  to  the  platinum  point,  and  open 
the  key  b.  The  current  breaks  into  the  primary  coil,  and  a 
single  (making  or  closing)  induction  shock  is  the  result.  On 
letting  go  the  spring,  an  interrupted  current  is  at  once  ob- 
tained. This  may  be  stopped  at  any  moment  by  pressing 
down  the  spring,  and  then  a  single  shock  is  again  obtained 
b}1,  letting  it  rise  once  against  the  platinum  point,  and  keeping 
it  there. 

III.  Phenomena  Attending  Muscular  Contraction. 

These  can  only  be  satisfactorily  determined  by  studying 
tetanus.  The  changes  in  a  single  contraction  are  too  slight 
and  transitory  to  be  distinctly  appreciated. 

Obs.  VI.  During  contraction  there  is  no  appreciable  change 
of  bulk. 

Take  the  whole  leg,  or,  better  still,  both  legs,  of  a  frog,  in- 
cluding the  attachment  of  the  thigh  muscles  to  the  ilium  and 
coccyx,  and  remove  the  skin.  Tie  a  thin  platinum  wire  round 
each  end  of  the  leg.  Place  the  thigh  in  a  bottle  filled  with 
normal  saline  solution,  insert  a  cork  in  the  mouth,  bring  the 
platinum  wires  through  the  cork,  and  in  the  centre  of  the  cork 
insert  a  narrow  glass  tube.  Fill  the  tube  up  to  a  certain  height 
with  the  saline  solution,  make  sure  that  no  air  bubble  remains 
below  the  cork  or  entangled  in  the  leg,  and  that  the  cork  is 
tight.  Place  a  scale  behind  the  glass  tube  in  order  that  the 
level  of  the  solution  may  be  exactly  determined,  and  bring  the 
platinum  wires  into  connection  with  an  induction  coil  arranged 
for  an  interrupted  current. 

Tetanize  the  leg  with  a  strong  current ;  even  at  the  height 
of  the  tetanus,  no  perceptible  change  of  level  in  the  fluid  in  the 
tube  will  take  place. 

Obs.  VII.  During  contraction  the  elasticity  of  the  muscle  is 
diminished^  i.e.,  its  extensibility  is  increased. 

Load  a  muscle  with  50  grammes,  and  record  the  amount  of 
extension.  Kemove  the  load  and  tetanize  the  muscle.  At  the 
height  of  tetanus,  load  the  muscle  again  with  the  50  grammes 
and  record  the  extension.  This  will  be  found  to  be  much 
larger  in  the  second  instance  than  the  first.  If  tracings  of  the 
extension  be  taken  on  a  revolving  cylinder,  curves  similar  to 


374  TETANUS. 

those  shown  in  Fig.  284  will  be  obtained.  When  the  muscle  is 
at  rest  and  unloaded,  the  recording  point  of  the  lever  describes 
the  straight  line  o,  x.  The  sudden  application  and  speedy  re- 
moval of  the  load  produces  the  curve  ./',  o,  the  muscle  in  this 
instance  failing  to  return  to  its  original  length.  On  being 
tetanized,  the  muscle  shortens  from  the  level  of  x'  a  to  the 
level  of  o;  and  the  application  of  the  same  load  as  before  pro- 
duces the  long  curve  o'  a'. 

Obs.  VIII.  During  contraction  there  is  a  diminution,  a  nega- 
tive variation,  of  the  natural  muscle  current. 

This  is  shown  by  the  galvanometer  {see  Chap.  XXV., 
Sec.  II.). 

It  may  also  be  shown  by  using  the  variations  in  the  mus- 
cular current  as  a  means  of  stimulating  a  nerve  supplying 
another  muscle. 

Get  ready  two  nerve-muscle  preparations  as  irritable  and  as 
little  injured  as  possible;  one  may  be  the  whole  of  the  under 
leg,  with  the  femur  cut  off  close  to  knee,  and  as  long  a  sciatic 
nerve  as  possible  (Fig.  285  a);  the  other  should  include  the 
muscles  of  the  thigh  as  well,  the  skin  being  in  both  cases  re- 
moved (Fig.  285  b). 

Place  b  on  a  glass  plate,  and  let  the  extreme  (central)  end 
of  the  nerve  rest  on  a  pair  of  electrodes  connected  with  an  in- 
duction coil. 

Lay  the  nerve  of  a  over  the  muscles  of  the  thigh  of  b,  as  in 
the  figure. 

Send  a  single  induction  shock  through  b;  there  will  be  a 
single  contraction  of  the  muscles  of  b,  and  almost  at  the  same 
time  a  single  contraction  of  the  muscles  of  A. 

Send  an  interrupted  current  through  the  electrodes  of  b. 
The  muscles  of  b  will  be  thrown  into  tetanus.  So  also  will 
those  of  a. 

The  single  contraction  of  the  muscles  of  b  causes  a  single 
variation  in  the  natural  currents  of  the  muscles  of  b;  this  acts 
as  a  single  stimulus  to  the  nerve  of  a,  and  so  causes  a  single 
contraction  in  the  muscles  of  a. 

When  the  muscles  of  b  are  thrown  into  tetanus,  each  con- 
stituent contraction  of  which  that  tetanus  is  made  up  causes  a 
corresponding  variation  in  the  natural  current,  which  therefore 
during  the  tetanus  is  undergoing  a  succession  of  variations. 
Each  such  variation  acts  as  a  stimulus  to  the  nerve  of  A,  and 
accordingly  the  muscles  of  A  are  thrown  into  a  tetanus,  the 
constituent  contractions  of  which  correspond  exactly  with 
those  of  the  muscles  of  b. 

In  the  galvanometer  we  have  no  such  series  of  variations  in 
the  position  of  the  needle;  the  negative  variation  during  teta- 
nus appears  as  a  steady  backward  swing  of  the  needle.     This 


BY    DR.    MICHAEL    FOSTER.  375 

is  because  the  inertia  of  the  needle  prevents  its  responding 
with  sufficient  rapidity  to  the  variations  in  the  current. 

The  proof  that  the  negative  variation  of  tetanus  is  thus 
really  made  up  of  a  succession  of  variations  is  supplied  not  by 
the  galvanometer,  but  by  the  above  experiment  with  the  frog's 
muscle,  or,  as  it  is  often  called,  the  "  rheoscojnc  frog." 

The  above  observation  will  frequently  fail  unless  the  nerves 
are  perfectly  fresh  and  irritable. 

06s.  IX.  Satisfactory  results  having  been  obtained,  liga- 
ture tightly  in  one  case  the  nerve  of  b  between  the  muscles 
and  the  electrodes,  and  in  another  the  nerve  of  a  between  its 
muscles  and  the  part  of  the  nerve  lying  on  the  muscle  of  b. 

In  either  case,  the  secondary  contraction  in  a  should  be 
entirely  absent.  If  they  are  present,  they  are  due  to  an  escape 
of  the  current;  and  the  observation  must  be  repeated  on  fresh 
muscles  and  nerves,  greater  precautions  being  taken  to  pre- 
vent the  escape  of  the  current. 

Obs.  X.  During  contraction,  muscle  becomes  acid. 

Prepare  two  muscles,  either  the  gastrocnemius  or  rectus,  or, 
perhaps  better  still,  take  the  whole  of  the  thigh  muscles. 
Leave  one,  a,  alone  ;  tetanize  the  other,  b,  repeatedly.  Make 
an  incision  through  each  and  test  their  reaction. 

A  will  be  found  to  be  neutral  or  alkaline  ;  b  will  be  found  to 
be  distinctly  acid. 

Obs.  XL  During  contraction,  the  temperature  of  the  vius- 
cle  rises. 

Prepare  a  whole  leg  with  sciatic  nerve  ;  choose  a  large, 
health}',  strong  frog.  From  the  thigh  resect  the  femur  in  its 
middle  for  the  greater  part  of  its  length,  injuring  the  nerve 
and  muscles  as  little  as  possible. 

In  place  of  the  removed  femur,  place  the  bulb  of  a  thermo- 
meter reading  one-tenth  of  a  degree  centrigrade  at  least ;  wrap 
the  muscles  carefully  round  the  bulb  ;  surround  the  thigh  with 
cotton-wool,  and  wait  till  the  level  of  the  mercury  is  constant. 
The  thermometer  should  be  fixed  very  firmly  and  steady.  Now 
send  an  interrupted  current  through  the  nerve.  The  muscles 
will  be  thrown  into  tetanus,  and  the  mercury  in  the  thermo- 
meter will  rise. 

(For  determining  more  exactly  the  changes  of  temperature 
in  a  muscle  during  contraction,  it  is  better  to  use  thermopile 
needles  with  a  galvanometer  of  little  resistance  (see  Chap. 
XVIII.,  p.  344)  ;  or  for  still  finer  observations,  in  which  it  is 
desirable  to  avoid  the  effects  of  friction,  the  swinging  appa- 
ratus of  Heidenhain  may  be  employed.  (See  Heidenhain- 
Mechan.  Leistung,  Wcirmeentivickelung,  etc.,  bei  der  Muskel- 
thdliglceil.) 


376  ELECTRIC    CURRENTS   OF    MUSCLES. 


CHAPTER  XXY. 
ELECTRIC  CURRENTS  OF  MUSCLES. 

I.  The  Natural  Currents. —  Obs.  I.  Place  the  galvanome- 
ter A  and  scale  b  east  and  west  (with  lamp  lighted)  about  three 
feet  apart,  level  the  galvanometer  with  the  levelling  screws  c, 
carefully  set  the  mirror  free  if  needful  by  gently  raising  the 
milled  head  seen  on  the  top  of  the  galvanometer  when  the 
glass  cover  is  removed,1  and  adjust  the  height  of  the  lamp 
by  pulling  in  and  out  its  brass  neck,  or  moving  it  from  side  to 
side  until  the  light  falls  well  on  the  mirror. 

The  most  convenient  galvanometer  for  the  purpose  is  Sir 
William  Thomson's.  The  one  represented  in  the  figure  (fig. 
286)  is  a  differential  one,  but  should  be  used  as  a  single  one 
in  the  following  observations  by  connecting  the  two  central 
binding  screws  a  a  with  a  piece  of  wire. 

Having  put  on  the  glass  cover,  screw  the  adjusting  magnet 
d  with  its  upright  e  on  to  the  top  of  the  galvanometer.  Let 
the  magnet,  with  its  north  pole  directed  towards  the  magnetic 
north,  be  at  first  at  the  top  of  the  upright ;  gradually  bring  it 
down,  moving  it  from  side  to  side,  and  carefully  watching  the 
spot  of  light  as  it  travels  to  and  fro  on  the  scale.  Before  the 
magnet  lias  descended  very  far,  the  student  will  have  so  far 
gained  command  over  the  mirror,  as,  by  moving  the  magnet 
to  a  certain  position  right  or  left,  to  be  able  to  bring  the  spot 
of  light  nearly  to  zero. 

This  done,  shift  the  scale  away  from  or  towards  the  galva- 
nometer, until  the  image  of  the  slit/ through  which  the  lamp 
shines  is  well  focussed  on  the  scale.  (If  not  provided  on  the 
scale,  affix  an  upright  wire  in  the  middle  of  the  slit  ;  have  the 
slit  wide,  and  use  the  shadow  of  the  wire  seen  in  the  broad 
spot  of  light,  to  determine  the  position  of  the  mirror.) 

Now  bring  the  magnet  very  gradually  still  lower  down. 
keeping  the  spot  of  light  as  near  as  possible  to  zero,  and 
watching  attentively  the  rapidity  with  which  the  spot  oscil- 
lates on  either  side  of  that  point.  It  will  be  found  that  as  the 
magnet  descends  the  oscillations  become  slower  and  slower. 
This  indicates  that  the  influence  of  the  earth's  magnetism  is 
becoming  more  and  more  neutralized  by  the  magnetism  of  the 

1  If  possible,  the  galvanometer  should  be  carefully  levelled  and  set 
once  for  all,  and  kept  so  in  some  place  where  it  need  not  be  disturbed. 


BY    DR.    MICHAEL    FOSTER.  377 

adjusting  magnet.  On  continuing  to  lower  the  magnet,  the 
point  of  neutralization  is  soon  passed,  and  then  the  influence 
of  the  adjusting  magnet  on  the  needle  becomes  stronger  than 
that  of  the  earth.  The  needle,  consequently,  which  previously 
had  its  north  pole  under  the  north  pole  of  the  magnet,  would, 
if  free  to  turn,  swing  half  round  in  the  attempt  to  bring  its 
south  pole  under  the  north  pole  of  the  magnet ;  and  indeed 
does  swing  round  as  far  as  the  arrangements  of  the  apparatus 
will  allow,  the  spot  of  light  rapidly  travelling  quite  beyond 
the  limits  of  the  scale.  When  this  had  been  found  to  occur, 
the  magnet  must  be  raised  again  up  to  or  rather  above  the 
point  of  neutralization.  The  oscillations  of  the  needle  will 
now  be  at  their  minimum  of  rapidity,  and  the  needle  will  be 
at  its  maximum  of  sensitiveness.  Bring  the  spot  of  light  ex- 
actly to  zero.  The  magnet  may  be  at  first  moved  with  the 
hand,  but  this  will  be  found  to  be  too  coarse  a  method.  Finer 
adjustment  is  gained  by  turning  the  milled  head/*. 

The  wires  convej'ing  the  current  through  the  galvanometer 
are  to  be  attached  to  the  outer  binding  screws  b  b. 

To  determine  which  direction  of  current  is  indicated  by  the 
movement  of  the  spot  of  light,  try  the  effect  of  a  very  feeble 
cell  upon  the  galvanometer.  But  be'  careful  not  to  use  the 
whole  of  the  current  proceeding  from  the  cell;  cut  off  the 
greater  part  of  it  by  means  of  the  shunt.     (Fig.  287.) 

Bring  the  wires  from  the  cell  to  the  binding  screws  of  the 
shunt.  With  the  plug  placed  in  the  hole  between  the  binding 
screws,  there  is  no  resistance  offered  by  the  shunt.  The  whole 
current  consequently  flows  through  the  shunt,  none  going 
through  the  circuit  of  the  galvanoraetei\  The  shunt  may  thus 
be  used  as  a  key,  and  it  will  not  be  necessary  to  have  another 
key  between  the  galvanometer  and  the  electrodes.  If  a  plug 
be  inserted  in  the  hole  marked  1-0,  and  the  plug  between  the 
binding  screws  be  withdrawn,  such  resistance  is  offered  by  the 
.shunt,  that  one-tenth  of  the  total  current  of  cell  goes  through 
the  galvanometer.  Similarly  with  the  plug  in  the  hole  marked 
1-99,  instead  of  in  the  hole  marked  1-9,  1-1 00th  goes  through 
the  galvanometer;  so  also  with  1-909. 

By  means  of  the  shunt  send  1-lOOOth  of  the  current  from  a 
cell  through  the  galvanometer,  and  mark  the  direction  in 
which  the  light  travels.  Note  which  screw  of  the  galvanome- 
ter is  connected  with  the  kathode,  and  which  with  the  anode, 
and  the  relation  of  the  direction  of  travel  of  the  spot  of  light, 
to  that  of  the  current  is  known.  Most  probably  it  will  be 
found  that  the  light  travels  in  the  same  way  as  the  current. 

Obg.  II.  Prepare  two  non-polarizablc  electrodes  with  trun- 
cated ends,  or  with  the  plug  projecting;  connect  them  with 
the  shunt,  using  it  as  a  key. 

The  plug  being  in  the  shunt  and  the  spot  of  light  at  zero, 


378  ELECTRIC    CURRENTS   OF    MUSCLES. 

place  the  two  electrodes  so  that  the  plugs  touch  each  other, 
or  place  a  morsel  of  thread  or  paper,  moistened  with  normal 
saline  solution,  over  the  two  plugs,  and  open  the  key.  The 
needle  should  remain  at  zero.  If  any  deviation  occurs,  it  is 
an  indication  of  a  current  in  the  electrodes  themselves.  If 
the  deviation  is  slight  and  constant,  its  direction  and  amount 
in  degrees  must  be  noted,  and  all  subsequent  observations 
corrected  by  it.  This  may  be  done  by  shifting  the  scale  a 
little,  so  as  to  bring  the  spot  of  light  to  zero,  or  by  bringing 
the  spot  of  light  to  zero  by  means  of  the  adjusting  magnet.  If 
it  be  large,  a  fresh  pair  of  electrodes  must  be  prepared,  which 
shall  give  no  such  deviation. 

06s.  III.  The  muscle  may  now  be  prepared.  Take  one  of 
the  large  muscles  of  the  thigh,  e.  g.,  the  triceps  (fig.  2G7  a); 
with  a  sharp  clean  knife  or  scissors  cut  the  tendon  of  inser- 
tion clear  away  with  a  transverse  cut;  similarly  make  a 
transverse  cut  at  the  origin.  Place  the  muscle  thus  prepared 
on  a  glass  plate  with  the  electrodes  under  a  moist  chamber. 
The  muscle  will  have  a  natural  longitudinal  surface  and  two 
artificial  transverse  surfaces.  Place  one  electrode  on  the 
longitudinal  surface  at  a  point  as  near  as  possible  midway 
between  the  two  ends,  and  the  other  as  near  as  possible  in  the 
centre  of  one  of  the  transverse  sections.  Connect  the  elec- 
trodes with  the  binding  screws  of  the  shunt,  the  plug  of  the 
shunt  being  in  place  between  the  screws.  Remove  the  plug. 
A  deviation  of  the  needle  will  take  place.  Most  probably  the 
spot  of  light  will  swing  right  out  of  sight  beyond  the  limit  of 
the  scale.  If  this  is  so,  replace  the  plug;  when  the  needle  has 
returned  to  zero,  shunt  by  means  of  the  second  plug ;  for 
instance,  put  the  second  plug  in  the  hole  marked  1-99  and 
thus  allow  only  1-lOOth  of  the  muscle  current  to  pass  through 
the  galvanometer,  and  then  remove  the  first  plug.  The  deflec- 
tion will  be  far  less.  Note  its  direction  and  amount  (number 
of  degrees  of  scale). 

A  current  will  be  found  passing  through  the  galvanometer 
from  the  mid-point  of  the  longitudinal  surface  to  the  central 
point  of  the  transverse  section.  Replace  the  plug,  so  as  to 
shut  off  all  the  current  from  the  galvanometer. 

Ob*.  IV.  Keeping  the  one  electrode  still  on  the  transverse 
section,  shift  the  other  electrode  from  the  mid-longitudinal 
point  to  some  point  nearer  that  transverse  section  ;  remove 
the  plug.  The  deflection  of  the  needle  will  indicate  a  current 
in  the  same  direction  as  before,  but  of  less  strength.  Replace 
the  plug. 

Obs.  V.  Place  the  electrodes  in  the  following  positions, 
always  replacing  the  plug  (serving  as  key)  between  the  binding 
screws  of  the  shunt  after  each  observation,  and  always  being 


BY   DR.    MICHAEL   FOSTER.  379 

careful  that  the  amount  of  contact  between  the  electrodes  and 
muscle  is  as  nearly  as  possible  the  same  in  all  cases: — 

One  electrode  on  the  mid-longitudinal  point,  the  other  at 
the  other  transverse  section.  The  current  will  he,  as  before, 
from  the  longitudinal  surface  to  the  transverse  section. 

Obs.  VI.  One  electrode  on  or  near  the  mid-longitudinal 
surface,  the  other  at  a  point  nearer  either  transverse  section. 
The  current  will  be  slight,  and  its  direction  will  be  from  the 
point  on  or  near  the  mid-longitudinal  point  to  the  one  farther 
off. 

06s.  VII.  The  two  electrodes  on  the  longitudinal  surface 
on  either  side  at  unequal  distances  from  the  middle  point  or 
equator.  The  current  will  be  slight,  and  from  the  point  nearer 
the  middle  to  the  point  farther  off. 

Obs.  VIII.  The  two  electrodes  on  the  longitudinal  surface 
at  equal  distances  from  the  middle  point  on  either  side ;  there 
will  be  little  or  no  current  at  all. 

Obs.  IX.  By  using  very  pointed  electrodes,  evidence  of  a 
current  may  be  obtained  on  the  transverse  section  from  the 
electrode  farther  from  the  centre  to  that  nearer  to  the  centre. 

Obs.  X.  The  student  may  repeat  these  observations  on  a 
muscle  to  which  an  artificial  longitudinal  surface  has  been 
given  by  a  clean  section,  and  also  on  a  muscle,  the  tendons  of 
origin  and  insertion  of  which  have  been  divided  without  injury 
to  the  muscular  fibres,  i.  e.,  on  a  muscle  with  natural  trans- 
verse surfaces  as  well  as  a  natural  longitudinal  surface. 

In  all  cases  the  following  result  will  come  out  more  or  less 
clearly: — 

In  any  muscle,  or  piece  of  muscle,  with  natural  or  artificial 
longitudinal  and  transverse  surf  aces,  evidence  may  be  obtained 
of  a  current  passing  through  the  electrodes  from  the  middle  of 
the  longitudinal  surface  {from  the  equator)  to  the  centre  of 
either  transverse  section,  and  from  any  point  nearer  the  equa- 
tor to  any  point  nearer  the  centre  of  either  transverse  section  ; 
the  current  is  stronger  the  farther  apart  these  two  points  lie 
(see  fig.  288,  where  the  direction  of  the  currents  obtainable 
from  a  piece  of  muscle  of  rectangular  form  is  indicated  by  the 
arrows,  and  the  intensity  by  the  sweep  of  the  curves.  The 
points  a  a,  equidistant  from  the  equator,  give  no  current). 

Obn.  XI.  Immerse  the  muscle,  on  which  you  have  been 
experimenting,  in  water  at  40°,  in  order  to  kill  it.  As  soon 
as  it  is  cool,  repeat  the  above  observations.  No  currents  at 
all,  or  very  trifling  ones,  will  be  obtained,  if  the  muscle  be 
perfectly  and  completely  "rigid." 

The  currents  obtainable  from  a  living  muscle  disappear 
when  rigor  mortis  is  complete. 

In  all  eases  examine  the  electrodes  by  themselves,  after  any 
scries  of  observations,  as  well  as  before,  in  order  to  be  sure 


380  ELECTRIC    CURRENTS   OF   MUSCLES. 

that  no  changes  have  taken  place  in  them  during  the  observa- 
tions, such  as  would  give  rise  to  a  current. 

II.  Negative  Variation. —  Obs.  XII.  Get  ready  a  nerve- 
muscle  preparation,  and  make  a  transverse  section  through  the 
lower  end  of  the  muscle.  Lay  the  muscle  on  a  glass  plate  ; 
connect  the  equator  and  transverse  section  of  the  muscle  by 
non-polarizable  electrodes  with  the  shunt  and  so  with  the  gal- 
vanometer ;  lay  the  end  of  the  nerve  (as  far  away  from  the 
muscle  as  possible)  on  another  pair  of  electrodes.  Connect 
this  second  pair,  or  "exciting  electrodes,"  as  the}'  may  he 
called,  with  an  induction  coil  arranged  for  an  interrupted  cur- 
rent. Let  the  induction  coil  be  as  far  as  possible  away  from 
the  galvanometer,  and  before  commencing  the  observation 
ascertain  that  the  setting  the  induction  machine  in  action  does 
not  affect  the  needle. 

The  spot  of  light  being  at  zero,  remove  the  plug  of  the  shunt, 
and  when  the  spot  has  come  to  rest  (using  a  shunt  if  the  cur- 
rent is  too  great  for  the  scale),  send  a  moderately  strong  inter- 
rupted current  through  the  exciting  electrodes.  The  muscle 
will  become  tetanized;  at  the  same  time  the  spot  of  light  .will 
travel  back  a  certain  distance  toward  zero,  i.  e.,  the  current 
obtainable  from  the  muscle  at  rest  is  diminished,  or  suffers  a 
negative  variation  during  tetanus.  Shut  off  the  tetanizing  cur- 
rent;  the  needle  returns  towards  its  former  position.  If  the 
muscle  be  laid  flat  on  the  glass  plate,  considerable  tetanus  may 
be  called  forth  without  the  electrodes  at  all  shifting  their  posi- 
tion in  relation  to  the  muscle,  especially  if  they  be  pressed 
somewhat  firmly  on  to  the  muscle  to  start  with. 

Obs.  XIII.  Having  determined  the  negative  variation  as 
above,  tie  a  piece  of  wet  silk  or  thread  tightly  round  the  nerve 
between  the  muscle  and  the  exciting  electrodes,  being  very 
careful  to  disturb  nothing  else.  Now  send  the  same  inter- 
rupted current  as  before  through  the  exciting  electrodes. 
There  will  be  no  tetanus  and  no  negative  variation.  The  liga- 
ture, having  destroyed  the  vital  continuit}'  of  the  nerve,  lias 
prevented  the  passage  of  nervous  impulses  along  the  nerve  to 
the  muscle. 

Should  any  influence  on  the  galvanometer  be  observable,  it 
is  an  indication  that  an  escape  of  current  from  the  exciting 
electrodes  to  the  galvanometer  electrodes  has  taken  place. 
The  ligature  of  the  nerve  does  not  destroy  the  electrical  con- 
tinuity of  the  nerve,  though  it  does  its  vital  continuity. 

The  exciting  electrodes  must  be  removed  further  from  the 
muscle,  or  a  weaker  current  used,  so  as  to  prevent  this  escape 
of  current,  and  the  observation  then  repeated. 


BY    DR.    MICHAEL    FOSTER.  381 


CHAPTER  XXVI. 
ELECTRIC  CURRENTS  OF  NERVES. 

I.  Natural  Currents. — Obs.  I.  Bring  the  galvanometer 
into  as  sensitive  a  condition  as  possible.  The  shunt  will  he 
unnecessary  in  this  case  except  to  he  used  as  a  key.  Prepare 
as  long  a  piece  of  nerve  as  possible  with  the  least  possible 
injury.  Hang  the  middle  of  the  nerve  over  a  bent  non-polari- 
zable  electrode,  and  bring  both  ends  to  rest  on  the  plug  of 
another  electrode,  as  represented  in  fig.  289.  In  this  way, 
one  electrode  will  be  in  contact  with  the  equator,  and  the  other 
with  both  transverse  sections.  The  current  from  the  equator 
to  each  transverse  section  being  the  same  in  direction,  the  re- 
sult of  this  arrangement  will  be  to  double  the  effect  on  the 
needle. 

The  current  in  the  nerve,  far  feebler  than  that  in  muscle,  is 
as  in  the  muscle  from  the  equator  (or  mid-longitudinal  point) 
to  the.  transverse  section. 

Obs.  II.  By  doubling  a  long  piece  of  nerve  and  laying 
different  points  on  the  electrodes,  it  may  be  determined  that 
the  arrangements  of  the  currents  are  the  same  in  one  case 
as  in  the  other.  Naturally,  the  various  points  in  the  minute 
transverse  section  cannot  be  examined. 

II.  Negative  Variation  in  Nerve. — Obs.  III.  Prepare 
as  long  a  piece  of  nerve  as  possible  ;  lay  the  transverse  section 
of  the  central. end  and  a  point  in  the  longitudinal  surface  at 
some  little  distance  from  that  end  on  the  pair  of  galvanometer 
electrodes.  Lay  any  two  points  at  the  other  end  (peripheral) 
of  the  nerve  on  a  pair  of  exciting  electrodes  connected  with  an 
interrupted  current. 

Determine  the  amount  of  deflection  given  by  the  natural 
current.  Send  an  interrupted  current  through  the  exciting 
pair.  There  should  be  a  slight  but  distinct  diminution,  a  slight 
negative  variation,  of  the  current.  When  a  nerve  is  excited, 
the  natural  current  suffers  a  negative  variation. 

Obs.  IV.  Repeat  the  observation,  placing  the  peripheral  end 
of  the  nerve  on  the  galvanometer  electrodes,  and  the  central  on 
the  exciting  electrodes. 

There  will  be,  as  before,  a  diminution,  a  negative  variation 
of  the  current. 


382  ELECTROTONUS. 

The  negative  variation  travels  along  the  nerve  in  either  di- 
rection. 

Obs.  V.  Ascertain  as  before,  by  ligature,  that  the  effects 
witnessed  are  not  due  to  any  escape  of  current. 


CHAPTER  XXVII. 
ELECTROTONUS. 

Obs.  I.  Prepare  as  long  a  piece  of  nerve  as  possible.  Get 
ready  two  pair  of  non-polarizable  electrodes.  Place  the  thicker 
(central)  end  of  the  nerve,  on  one  pair  of  electrodes,  a  a'  fig. 
290.  This  figure  is  intended  to  represent  diagrammatic-ally 
the  effects  of  a  polarizing  current,  p  p\  acting  on  the  centre 
of  a  piece  of  nerve,  as  seen  by  testing  either  end  with  a  gal- 
vanometei*.  It  will  serve,  however,  to  illustrate  the  simpler 
case  of  Obs.  I.,  if  the  electrodes  bb'  he.  supposed  to  be  removed 
and  p  p'  brought  nearer  to  that  end  of  the  nerve.  Let  one 
electrode  be  on  the  transverse  section  of  the  nerve,  and  the 
other  on  the  longitudinal  surface  at  some  distance,  so  as  to 
obtain  a  tolerably  good  current.  Connect  this  pair  of  elec- 
trodes with  the  galvanometer,  putting  in  a  key  or  using  the 
shunt. 

Place  the  other  end  of  the  nerve  on  the  other  pair  of  elec- 
trodes, p  p' ;  connect  these  electrodes  with  a  cell,  which  may 
be  called  the  polarizing  cell,  interposing  a  commutator  (Chap. 
XIX.,  sec.  VII.).  Cover  the  nerve  with  a  shade,  or  put  it  with 
the  electrodes  in  the  nerve  chamber  (Chap.  XIX.,  sec.  IV.),  to 
protect  it  against  evaporation. 

Both  keys  being  down,  and  the  needle  of  the  galvanometer 
being  at  zero,  open  the  key  of  a  a',  and  note  the  deflection  of 
the  needle.  The  current  will  of  course  pass  through  the  gal- 
vanometer in  the  direction  of  the  arrow  in  the  figure  from  a  to 
«',  and  the  circuit  may  be  supposed  to  be  completed  by  the 
current  passing  inside  the  nerve  in  the  direction  of  the  arrow. 
Shut  the  key  of  a  a'. 

Obs.  II.  Now  open  the  commutator  of  the  polarizing  cell  in 
such  a  way  that  the  current  of  the  cell  passes  from  p  to  ;/,  in 
the  direction  of  the  arrows  in  the  figure,  i.e.,  flows  in  the  same 
direction  as  the  natural  nerve  current  flows  through  the  gal- 
vanometer. Open  the  key  of  a  a'.  Note  again  the  deflection 
of  the  needle;  it  will  be  found  to  be  greater  than  it  was  before. 

Shut  the  key  of  a  a'  and  shut  off  the  polarizing  current. 


BY    DR.    MICHAEL   FOSTER.  383 

Then  reopen  a  a'.  The  needle  will  be  found  to  return  to  the 
position  it  had  in  Obs.  I. 

Obs.  III.  Repeat  the  observation,  but  reverse  the  polarizing 
current;  let  it  flow  from  p'  to  p,  that  is,  in  a  direction  con- 
traiy  to  the  natural  nerve-curreut.  The  needle  of  the  galvano- 
meter will  now  be  found  to  have  suffered  a  diminution  of  de- 
flection instead  of  an  increase. 

"  When  a  constant  current  is  allowed  to  break  into  a  nerve, 
the  natural  nerve  current.,  even  at  some  distance  from  the 
electrodes,  is  affected  during  the  whole  time  of  the  passage  of 
the  constant  {jiolaTiziag)  current;  when  the  natural  and 
polarizing  currents  have  the  same  direction,  the  natural  cur- 
rent is  increased ;  when  contrary  directions,  the  natural  cur- 
rent is  diminished.'''1 

This  condition  of  the  nerve,  maintained  during  the  whole 
passage  of  the  current,  is  known  as  electrotonus. 

Obs.  IY.  Tie  the  nerve  very  tightly  with  a  ligature  between 
the  polarizing  and  the  galvanometer  electrodes  ;  or  divide  it, 
and  place  the  ends  carefully  in  exact  opposition,  and  repeat 
the  observations.  It  will  be  found  that  the  natural  current  is 
in  no  way  affected  by  the  polarizing  current. 

The  phenomena,  therefore,  are  not  due  to  any  escape  of  the 
battery  current :  something  more  than  mere  physical  continu- 
ity is  required  for  their  development. 

Obs.  Y.  Repeat  the  observations,  placing  the  thinner  (peri- 
pheral) end  of  the  nerve  on  the  galvanometer  electrodes,  and 
the  thicker  on  the  polarizing  electrodes. 

The  results  are  the  same  ;  electrotonus  is  established  equally 
well  in  either  direction. 

Obs.  YI.  The  same  result  may  be  better  shown  in  the  fol- 
lowing way:  Take  three  pair  of  electrodes.  Place  the  polar- 
izing pair  p  p' ,  fig.  290,  in  the  middle  of  the  nerve,  and  connect 
the  other  two  pair  with  the  two  cut  ends,  as  shown  in  the  figure. 
Bring  the  wires  from  a  a'  to  a  key,  and  those  from  b  b'  to 
another  key ;  then  the  wires  from  both  keys  to  the  same  bind- 
ing screws  of  the  galvanometer.  By  opening  the  key  of  a  a' 
while  that  of  b  b'  is  shut,  or  vice  versa,  the  amount  of  natural 
current  in  a  a'  or  b  b'  may  be  respectively  determined.  (Or 
use  the  double  key,  as  directed  in  Chap.  XIX.,  sec.  IX.). 
Determine  both  before  the  key  of  p  p'  is  opened.  Then  open 
the  key  of  p  p'  and  determine  the  amount  of  deflection  both  in 
a  a'  and  b  b'. 

It  will  be  found  that  when  the  current  passes  from  p  to  p' 
in  the  direction  of  the  arrow,  as  in  the  figure,  the  current  at 
l>  !>'  is  diminished  (in  the  neighborhood  of  the  kathode),  while 
that  at  a  a'  is  increased  (in  the  neighborhood  of  the  anode). 
If  the  direction  of  the  polarizing  current  be  reversed,  if  it  be 


384  ELECTROTONUS. 

made  to  flow  from  p'  to  p,  then  a  a'  will  be  diminished  and  b  b' 
increased. 

Ob*.  VII.  Repeat  the  observation,  placing  the  galvanometer 
electrodes,  not  at  the  cut  ends  as  before,  but  on  any  two 
points  from  which  a  natural  current  can  be  obtained.  Similar 
results  will  be  observed. 

With  most  dispositions  of  the  electrodes  the  natural  current 
is  increased  in  the  neighborhood  of  the  positive  and  diminished 
in  that  of  the  negative  pole.  The  region  of  the  negative  pole 
is  said  to  be  thrown  into  katelectrotonus,  that  of  the  positive 
into  anelectrotonus. 

Obs.  VJII.  Having  determined  the  amount  of  diminution  of 
b  b'  and  the  amount  of  increase  of  a  a'  when  the  polarizing 
electrode  is  exactly  in  the  middle  line  between  the  other  two 
pair,  shift  the  polarizing  electrodes  nearer  to  b  b'.  Be  very 
careful  that  the  electrodes  in  their  new  position  are  exactly  the 
same  distance  from  each  other  as  before,  and  that  the  nerve 
touches  the  plugs  of  the  electrodes  exactly  as  before,  so  that 
the  only  difference  established  is  that  a  different  part  of  the 
nerve  is  placed  between  the  electrodes.  Be  careful  also  not  to 
disturb  the  position  of  the  nerves  on  the  two  pair  of  galvano- 
meter electrodes.  If  all  has  been  done  properly  before  the 
polarizing  current  is  allowed  to  break  into  the  nerve,  the 
amount  of  deflection  at  a  a'  and  b  b'  should  be  the  same  as 
when  the  polarizing  electrodes  were  in  the  middle.  Now  open 
the  key  of  the  polarizing  current  and  determine  the  deflection 
at  a  a'  and  b  b'.  The  diminution  of  deflection  at  b  b'  should 
be  greater,  and  the  increase  at  a  a'  less,  than  when  the  polar- 
izing electrodes  were  in  the  middle.  Reverse  the  direction  of 
the  polarizing  current.  The  increase  at  b  b'  will  be  greater, 
the  decrease  at  a  a'  less,  than  when  the  electrodes  were  in  the 
middle. 

Obs.  IX.  Shift  the  electrodes  (carefully  as  before)  towards 
a  a/  instead  of  towards  b  &',  and  repeat  as  in  Obs.  VIII.  It 
will  be  found,  as  before,  that  the  nearer  the  galvanometer 
electrodes  are  to  the  polarizing  electrodes,  the  greater  the  effect 
either  in  way  of  decrease  or  increase,  as  the  case  may  be,  of 
the  natural  current. 

The  amount  of  electrotonic  increase  or  decrease  is  greater 
the  nearer  the  points  tested  lie  to  the  polarizing  electrodes. 

Obs.  X.  Having  determined  the  amount  of  electrotonus  es- 
tablished by  the  passage  of  a  current  from  a  single  cell,  use 
two  cells  (keeping  everything  just  the  same),  and  compare  the 
results  ;  then  three  cells  ;  then  four. 

The  amount  of  electrotonic  increase  or  decrease  of  the 
natural  current  increases  with  an  increasing  intensity  of  the 
polarizing  current. 

Obs.  XI.  Determine  the  electrotonic  increase  and  decrease 


BY    DR.    MICHAEL   FOSTER.  385 

■with  a  given  current  on  a  perfectly  fresh  nerve  from  a  strong 
frog.  Allow  the  nerve  to  remain  for  some  time  exposed  in  the 
moist  chamber,  and  repeat  the  observation.  The  electrotonic 
effects  will  be  found  to  be  less. 

The  amount  of  electrotonic  variation  is  dependent  on  the 
vital  conditions  of  the  nerve. 


CHAPTER  XXVIII. 
STIMULATION  OF  NERVES. 

Other  things  being  constant,  we  ma}'  now  take  variations 
in  the  contraction  of  the  muscle  of  a  nerve-muscle  preparation 
as  a  measure  of  variations  in  the  condition  of  the  nerve.  A 
muscular  contraction  is  a  token  of  a  nervous  impulse  passing 
along  the  nerve,  the  extent  and  character  of  the  one  being  a 
measure  of  the  extent  and  character  of  the  other:  a  tetanus  in 
the  muscle  indicates  a  series  of  impulses  in  the  nerves,  follow- 
ing each  other  with  not  less  than  a  certain  velocit}'. 

1.  The  Effects  of  the  Constant  Current.— Obs.  I.  Ar- 
range a  nerve-muscle  preparation  in  the  moist  chamber,  with 
the  nerve  on  non-polarizable  electrodes,  the  muscle  loaded 
with  10  or  15  grammes,  lever  attached,  recording  surface  pre- 
pared, etc. 

Have  a  battery  of  two  or  more  cells,  and  between  the  battery 
and  the  electrodes  introduce  the  rheochord  (Chap.  XIX.,  sec. 
VIII.).  Let  all  the  plugs  be  in,  and  the  travelling  mercury 
cups  close  up. 

The  resistance  now  offered  by  the  rheochord,  compared  with 
that  offered  by  the  electrodes,  is  practically  nil ;  consequently 
none  of  the  current  from  the  battery  will  pass  through  the 
latter;  there  will,  therefore,  be  no  contraction  in  the  muscle. 

Remove  one  of  the  plugs,  viz.,  that  one  the  removal  of  which 
tli rows  the  least  resistance  into  the  rheochord.  A  certain 
fraction  of  the  current  will  now  pass  through  the  electrodes  on 
account  of  the  resistance  thrown  into  the  current  through  the 
rheochord  by  the  removal  of  the  plug.  If  a  contraction  be 
the  result,  let  it  be  recorded  ;  if  none,  let  that  fact  be  recorded 
too,  noting  on  the  recording  surface  the  plug  removed.  Re- 
move the  plugs  one  by  one,  recording  the  result  each  time. 
Replace  the  plugs  one  by  one,  also  noting  the  results. 

It  will  be  found  that  a  contraction  of  the  muscle  takes 
place,  a  nervous  impulse  is  originated,  only  at  the  moment 
when  the  plug  is  withdrawn  or  replaced.  It  may  be  present 
25 


386  STIMULATION   OF   NERVES. 

at  both  withdrawal  or  reinsertion,  or  at  either,  or  at  neither; 
but  no  contraction  occurs  in  the  interval  during  which  the 
plug  or  plugs  remain  away  from  the  board  or  in  their  place, 
provided  that  the  current  in  the  battery  be  constant  and  the 
condition  of  the  nerve-muscle  normal. 

A  nervous  impulse  is  generated  in  a  nerve  only  when  there  is 
a  sudden  change  in  the  intensity  of  a  constant  current  passim/ 
through  it  {including  the  changes  from  and  to  zero,  i.  e.,  the  total 
breaking  and  making  of  the  current).  So  long  as  the  current 
remains  uniform  in  intensity,  there  is  no  contraction  of  the 
muscle,  no  uervous  impulse  generated  in  the  nerve. 

The  contractions  so  obtained  are  simple  contractions,  indica- 
tive of  the  advent  of  a  single  nervous  impulse.  Very  often, 
especially  in  working  with  winter  frogs  in  early  spring,  the  con- 
tractions thus  obtained  by  variations  in  the  intensity  of  a  con- 
stant current  are  not  simple,  but  tetanic.  This  is  an  abnormal 
result,  which  has  not  yet  been  investigated. 

The  contractions  obtained  above  are  not  only  variable,  inas- 
much as  they  come  either  at  a  diminution  (breaking)  or  increase 
(making)  of  the  current,  or  at  both,  but  also  differ  in  extent, 
i.  e.,  the  nervous  impulses  differ  in  intensit}r. 

These  variations  depend  on  the  strength  of  the  current 
(amount  of  variation  of  the  current),  the  direction  of  the  cur- 
rent, and  the  condition  of  the  nerve. 

II.  Law  of  Contraction. —  Obs.  II.  Arrange  in  the  moist 
chamber  a  nerve-muscle  preparation  as  fresh  and  lively  as  pos- 
sible. Place  the  nerve  on  a  pair  of  non-polarizable  electrodes, 
about  a  centimetre  apart.  Insert  between  the  electrodes  and 
a  battery  of  two  or  more  cells,  first  the  commutator,  and 
then  the  rheochord.  Let  the  positive  and  negative  wires  have 
different  colors,  the  same  throughout  the  whole  apparatus  in 
each  case,  and  arrange  so  that  when  the  handle  of  the  commu- 
tator is  raised,  the  current  is  ascending  in  the  nerve ;  when 
depressed,  descending. 

The  handle  of  the  commutator  being  horizontal,  and  the  plugs* 
of  the  rheochord  all  in,  withdraw  the  mercury  cups  a  few  de- 
grees of  the  scale,  and  depress  the  handle  of  the  commutator. 
If  there  be  any  contraction,  record  it.  This  is  equivalent  to 
the  making  in  the  nerve  of  an  extreme^  feeble  descending  cur- 
rent. Then  bring  the  handle  of  the  commutator  horizontal, 
and  so  break  this  feeble  current,  recording  any  result. 

After  waiting  a  few  minutes,  repeat  the  observation,  using 
an  ascending  current  instead  of  a  descending.  Thus  will  be 
obtained  the  effects  of  breaking  and  making  an  extremely  feeble 
constant  current  both  ascending  and  descending. 

Then  shift  the  mercury  cups  several  degrees,  and  repeat  the 
whole  observation.     This  will  give  the  effects  of  making  and 


BY    DR.    MICHAEL    FOSTER.  387 

breaking  a  still  feeble  but  yet  rather  stronger  descending  and 
ascending  current. 

Proceed  in  this  way,  shifting  the  mercury  cups  by  stages, 
until  the}7,  are  brought  to  the  other  end  of  the  board  ;  then 
remove  the  plugs  one  by  one,  the  removal  of  each  plug  mark- 
ing a  corresponding  augmentation  of  the  strength  of  the  current 
sent  through  the  electrodes  on  the  nerves. 

Wait  some  minutes  between  each  observation  to  allow  the 
nerve  to  recover  itself.  Tabulate  the  results.  They  should  be 
such  that,  throwing  the  various  intensities  of  current  into  four 
categories,  they  illustrate  the  following  law: — 


Descending. 
Make.                 Break. 

Ascending 
Make.             Break. 

Weakest 

Yes 

No 

No           No 

Weak 

Yes 

No 

Yes          No 

Moderate 

Yes 

Yes 

Yes          Yes 

Strong 

Yes 

No 

No           Yes 

where  "  Yes"  means  a  contraction  ;  "  No,"  none. 

The  making  of  the  descending  current  is  the  first  to  make 
itself  manifest  by  its  effects,  and  maintains  its  pre-eminence 
throughout  the  series  as  the  most  certain  and  strongest 
stimulus. 

Next,  the  making  of  the  ascending  current  also  becomes  effi- 
cient;  then  the  breaking  of  the  descending ;  lastly,  the  break- 
ing of  the  ascending ;  so  that  with  a  certain  intensity  of  current 
which  we  here  call  "  moderate,"  a  contraction  is  called  forth 
both  by  making  and  breaking  both  ascending  and  descending 
currents. 

With  a  further  increase  of  intensity,  the  contraction  which 
follows  upon  the  making  of  the  ascending  current  gets  less, 
and  finally  disappears  altogether.  The  contraction  due  to 
breaking  the  descending  current  suffers  subsequently  the  same 
fate,  so  that  wijh  a  "  strong"  current  we  have  only  a  single 
contraction  with  each  current;  but  it  is  a  contraction  on  mak- 
ing in  the  case  of  the  descending,  on  breaking  in  case  of  the 
ascending. 

We  have  seen  that  when  a  constant  current  is  sent  into  a 
nerve,  katelectrotonus  is  established  at  the  negative  pole,  ane- 
lectrotonus  at  the  positive.  Both  conditions  remain  during  the 
whole  time  of  the  passage,  and  both  disappear  (with  more  or 
less  rebound)  when  the  current  is  broken. 

It  is  evident  from  the  above  observations  that  the  rise  of  a 
nervous  impulse  is  connected  with  the  transition  of  a  nerve  from 
its  ordinary  condition  into  that  of  either  katelectrotonus  or 
anelectrotonus,  or  both,  or  with  its  return  from  katelectrotonus 
or  anelectrotonus  into  its  normal  condition,  and  not  witli  its 
being  or  remaining  in  either  katelectrotonus  or  anelectrotonus. 


388  STIMULATION   OF   NERVES. 

Further,  it  is  evident  from  the  different  results  of  breaking 
and  making,  that  the  entrance  into  katelectrotonus  and  ane- 
lectrotonus  has  not  the  same  relation  to  the  origin  of  a  nervous 
impulse  as  has  the  exit  from  those  states. 

Lastly,  from  the  different  behavior  of  the  ascending  and 
descending  currents,  it  appears  that  the  effect  of  the  entrance 
into  katelectrotonus  is  not  the  same  as  that  of  the  entrance 
into  anelectrotonus,  and  that  the  effects  of  the  exits  from  these 
states  likewise  differ. 

III.  Electrotonus  as  affecting  Irritability. — Arrange 
a  nerve-muscle  preparation  in  the  moist  chamber,  with  lever, 
etc.  Prepare  two  pair  of  non-polarizable  electrodes.  Place  the 
end  of  the  nerve  on  one  pair,  about  1  or  2  cm.  apart ;  connect 
this,  the  polarizing  pair,  with  a  batteiy  of  one  or  two  cells, 
the  commutator  intervening.  Place  the  second  pair  between 
the  first  pair  and  the  muscle,  and  connect  this,  the  exciting 
pair,  with  an  induction  coil. 

When  the  polarizing  current  is  made  a  descending  one,  the 
portion  of  the  nerve  on  which  the  exciting  electrodes  rest,  will 
be  in  the  region  of  katelectrotonus  ;  when  ascending,  in  anelec- 
trotonus. 

Obs.  III.  The  polarizing  current  being  shut  off  (the  handle 
of  the  commutator  horizontal),-  pass  a  single  induction  (open- 
ing) shock  through  the  "  exciting"  pair,  and  record  the  con- 
traction. Shift  the  secondary  coil,  if  necessary,  until  a  con- 
traction of  moderate  excursion  is  obtained,  and  note  the  dis- 
tance of  the  secondary  coil  from  the  primary. 

Now  let  the  polarizing  current  ascend  in  the  nerve  (through 
the  polarizing  pair  of  electrodes)  ;  the  exciting  pair  will  ac- 
cordingly now  be  in  the  region  of  anelectrotonus. 

Neglect  the  contraction  which  may  be  caused  by  the  making 
(and  subsequent  breaking)  of  the  constant  polarizing  current ; 
and  while  the  current  is  thus  passing  in  an  ascending  direc- 
tion, send  a  single  induction  shock  of  the  same  strength  as 
before  through  the  exciting  pair,  and  record  the  contraction. 

Shut  off  the  polarizing  current,  and  after  a  few  minutes' 
rest,  send  a  third  time  the  same  induction  shock  through  the 
exciting  pair. 

Of  the  three  contractions  thus  called  forth  by  the  same 
stimulus  (the  induction  shock)  under  different  circumstances, 
it  will  be  found  that  the  second  is  much  smaller  than  the  first, 
but  the  third  nearly  of  the  same  size  (it  may  be  larger)  as  the 
first. 

During  the  passage  of  a  constant  current,  the  irritability  of 
a  nerve  is  lessened  in  the  anelectrolonic  region,  the  same  stimu- 
lus giving  rise  to  a  weaker  nervous  impulse,  and  so  to  a  smaller 
contraction. 

Obs.  IV.  Shift  the  secondary  coil  until  it  reaches   such   a 


BY    DR.    MICHAEL    FOSTER.  889 

position  that  the  induction  shock  given  becomes  the  mini- 
mum stimulus  required  to  produce  a  muscular  contraction, 
that  is,  any  further  removal  of  the  secondary  from  the  pri- 
mary coil  will  lead  to  the  absence  of  all  contractions.  This 
minimum  stimulus  then  giving,  in  the  absence  of  the  polarizing 
current,  a  slight  but  obvious  contraction,  send  an  ascending 
polarizing  current  through  the  nerve ;  the  contraction  will  be 
wholly  absent.  Remove  the  polarizing  current,  and  excite 
again  ;  the  contraction  will  again  make  its  appearance. 

Obs.  V.  Remove  the  secondary  coil  a  little  further  away 
from  the  primary,  so  that  an  induction  shock  gives  no  con- 
traction where  the  polarizing  current  is  cut  off  from  the  nerve. 
Pass  a  descending  current  through  the  polarizing  pair,  i.  e., 
throw  the  portion  of  nerve  in  which  the  exciting  pair  rest 
into  katelectrolonus.  Again  pass  the  same  induction  shock  as 
before :  a  contraction  will  follow. 

Shut  off  the  polarizing  current,  and  after  waiting  a  few 
minutes,  send  the  induction  shook  through  the  exciting  pair  a 
third  time.  No  contraction,  or  at  best  a  very  slight  one,  will 
be  obtained. 

During  the  passage  of  a  constant  current,  the  irritability  is 
increased  in  the  region  of  katelectrotonus. 

Obs.  VI.  The  other  arrangements  being  the  same,  put  the 
magnetic  interruptor  into  connection  with  the  primary  coil. 
Record  the  movements  of  the  lever  on  the  revolving  cylinder. 

With  a  not  very  strong  interrupted  current,  throw  the  mus- 
cle into  tetanus,  and  as  soon  as  tetanus  is  established,  send 
an  ascending  current  through  the  polarizing  electrodes  for  a 
few  seconds  only,  and  afterwards  close  the  key  of  the  inter- 
rupted current. 

The  curve  of  the  tetanus  on  the  recording  cylinder  will  ex- 
hibit a  marked  fall  (down  even  to  zero  if  the  polarizing  current 
be  strong  enough)  at  the  moment  when  the  polarizing  current 
breaks  into  the  nerve,  and  a  corresponding  rise  when  the 
polarizing  current  is  shut  off. 

This  is  simply  another  way  of  showing  the  diminution  of 
irritability  in  an  electro  ton  us. 

Obs.  VII.  Repeat  the  observation,  using  a  very  weak  teta- 
nizing  current,  and  let  the  polarizing  current  be  descending. 
The  making  of  the  polarizing  current  will  be  marked  by  a  rise, 
and  the  breaking  by  a  corresponding  fall  in  the  tetanus  curve, 
indicating,  as  before,  an  increase  of  irritability  in  katelectro- 
tonus. 

Obs.  VIII.  Ligature  the  nerve  between  the  two  pair  of  elec- 
trodes, and  repeat  all  the  observations.  The  polarizing  current 
will  have  no  effect  at  all  upon  the  results  of  the  exciting  cur- 
rent.    Otherwise,  part  of  the  effects  described  above  will  have 


390  STIMULATION    OF   NERVES. 

been  due  not  to  vital  changes  in  the  nerve,  bat  to  escape  of 
current  or  simple  electrical  changes. 

Obs.  IX.  Having  arranged  a  nerve-muscle  preparation  with 
the  polarizing,  but  without  the  exciting  pair  of  electrodes,  let 
the  nerve  between  the  electrodes  and  the  muscle  hang  down 
in  a  loop. 

Let  the  extreme  end  of  the  loop  dip  into  a  drop  of  concen- 
trated solution  of  common  salt.  As  soon  as  the  irregular 
tetanic  contractions  resulting  from  the  action  of  saline  fluid 
on  the  nerve  make  their  appearance,  pass  an  ascending  current 
through  the  electrodes.  The  tetanic  spasms  will  be  much  less- 
ened, or  cease  altogether. 

Pass  a  descending  current  through  the  electrodes,  the  spasms 
will  be  increased. 

The  general  irritability,  therefore,  of  the  nerve  is  affected 
in  electrotonus,  not  simply  its  susceptibility  to  electrical  modi- 
fications. 

Obs.  X.  By  introducing  a  rheochord  between  the  battery 
and  the  polarizing  electrodes,  and  by  varying  the  number  of 
cells  used,  the  student  will  ascertain  that  the  amount  of  in- 
crease of  irritability  in  katelectrotonus  and  decrease  in  anelec- 
trotonus  depends  on  the  strength  of  the  polarizing  current, 
being  greater  with  the  stronger. 

Obs.  XI.  B3'  placing  the  polarizing  electrodes  at  a  variable 
distance  from  each  other,  it  will  be  found  that,  with  the  same 
strength  of  current,  the  effect  is  greater  the  longer  the  piece  of 
nerve  between  the  polarizing  electrodes. 

Obs.  XII.  By  shifting  the  exciting  electrodes  nearer  to  and 
farther  from  the  polarizing  electrodes,  it  will  be  found  that 
the  effects  of  both  anelectrotonus  and  katelectrotonus  are 
greatest  in  the  immediate  neighborhood  of  the  polarizing 
pair,  and  diminish  the  farther  the  exciting  pair  is  from  the 
polarizing. 

In  all  the  above  observations,  the  stimulus,  whether  electric 
or  chemical  or  other,  is  brought  to  bear  on  the  nerve  between 
the  polarizing  pair  and  the  muscle. 

Obs.  XIII.  They  may  be  repeated  with  the  polarizing  pair 
placed  between  the  exciting  pair  (or  chemical  stimulus)  and 
the  muscle.  An  ascending  current  will  now  throw  the  region 
of  the  exciting  pair  into  katelectrotonus,  a  descending  into 
anelectrotonus. 

The  general  results  will  be  the  same,  but  they  will  not  come 
out  with  the  same  distinctness,  for  the  following  reason: 
When  the  exciting  pair  is  placed  nearer  to  the  muscle  than  the 
polarizing  pair,  the  nerve  between  the  exciting  pair  and  the 
muscle  is  simply  in  a  state  of  katelectrotonus,  the  intensity  of 
which  diminishes  towards  the  muscle  onwards.  There  is 
nothing  between   the  exciting  electrodes   and  the  muscle  to 


BY    DR.    MICHAEL    FOSTER.  391 

moilify  the  increase  of  impulse  due  to  katelectrotonus.  When 
the  exciting  pair  is  on  the  other  side  of  the  polarizing  pair, 
and  the  region  of  the  exciting  pair  thrown  into  katelectroto- 
nus, for  instance,  the  increased  impulse  due  to  katelectrotonus 
after  passing  through  the  region  of  katelectrotonus  has  to 
make  its  way  through  a  region  of  anelectrotonus  before  it  can 
reach  the  muscle — it  has  to  struggle  in  this  region  against  an- 
tagonistic influences,  and  whether  it  reaches  the  muscle  as  an 
impulse  greater  than,  or  less  than,  or  simply  equal  to,  that 
which  occurs  in  a  nerve  not  electrotonized,  will  depend  on  the 
relative  amounts  of  the  katelectrotonic  increase  of  irritability 
and  the  anelectrotonic  decrease  of  conductivity. 

This  will  be  found  to  depend  largely  on  the  intensity  of  the 
polarizing  current. 

If  the  current  be  weak,  the  katelectrotonic  increase  over  the 
normal  impulse  (of  the  non-electrotonized  nerve),  though  less- 
ened by  having  to  pass  through  an  anelectrotonic  region,  will 
be  evident  as  a  larger  contraction  in  the  muscle. 

If  the  polarizing  current  be  strong,  the  contraction  caused 
b}-  the  impulse  originated  in  the  katelectrotonic  region  will 
not  only  not  be  greater  than  the  normal  but  will  even  be  less, 
or  may  be  absent  altogether  with  a  very  strong  (three  or  four 
Grove  cells)  polarizing  current,  owing  to  the  impulse  being 
completely  blocked  in  the  anelectrotonic  region. 

Mutatis  mutandis,  the  same  results  are  witnessed  when  the 
effect  of  an  anelectrotonic  decrease  has  to  pass  through  a  kate- 
lectrotonic region  on  its  way  to  the  muscle. 

Obs.  XIV.  By  placing  the  polarizing  electrodes  sufficiently 
far  apart  from  each  other,  the  exciting  pair  may  be  inserted 
into  the  intrapolar  region,  and  the  following  results  ob- 
tained : — 

In  the  intrapolar  region,  as  in  the  extrapolar,  there  is  an  in- 
crease of  irritability  in  the  neighborhood  of  the  negative,  and 
a  decrease  in  the  neighborhood  of  the  positive  pole. 

The  increase  and  decrease  respectively  are  greatest  close  to 
the  poles,  and  diminish  towards  a  neutral  point  situate  between 
the  poles. 

With  a  weak  current,  this  neutral  point  lies  rather  nearer 
to  the  negative  pole  than  the  positive.  By  increasing  the 
strength  of  the  current  it  is  driven  nearer  and  nearer  to  the 
positive  pole. 

IV.  Other  Variations  in  Irritability. —  The  farther 
from  the  muscle  the  part  of  the  nerve  excited,  the  greater  the 
contraction. 

Obs.  XV.  Arrange  a  nerve-muscle  preparation  with  two  pair 
of  eleel  rodes,  one  dose  to  the  muscle,  the  other  near  to  the  cut 
<-u<l  of  the  nerve. 

Connect  both  electrodes  with  a  double  key  (Chap.  XIX., 


392  STIMULATION    OF   NERVES. 

sec.  IX.),  and  the  double  ke}-  with  an  induction  coil.     Arrange 
for  single  opening  induction  shocks. 

By  means  of  the  double  key,  put  the  lower  electrodes  next 
the  muscle  in  connection  with  the  secondary  coil,  and  find 
what  strength  of  the  current  (what  position  of  the  secondary 
coil)  just  falls  short  of  causing  a  contraction. 

Then  connect  the  upper  electrodes  with  the  secondary  coil, 
in  place  of  the  lower  ones.  Send  through  these  a  shock  of 
the  same  strength  as  that  which  sent  through  the  lower  elec- 
trodes produced  no  contraction.  A  distinct  contraction  will 
follow. 

Once  more  send  the  same  shock  through  the  lower  elec- 
trodes. There  will  be,  as  before,  no  contraction,  or  a  very 
slight  one. 

The  same  stimulus  produces,  therefore,  more  effect  when 
applied  to  a  point  farther  from  the  muscle. 

Obs.  XVI.  This  is  partly  due  to  the  section  of  the  nerve 
trunk  above  the  higher  electrodes. 

Having  thoroughly  destroyed  the  spinal  cord  of  a  frog,  and 
laid  bare  the  sciatic  nerve  without  dividing  it,  place  a  pair  of 
electrodes  under  the  main  sciatic  trunk,  send  a  feeble  single 
induction  shock  through  them,  and  record  the  amount  of  con- 
traction in  the  gastrocnemius,  or  determine  the  position  of  the 
secondary  coil,  which  gives  a  shock  just  falling  short  of  the 
strength  required  to  cause  a  contraction. 

Divide  the  sciatic  nerve  a  little  distance  above  the  electrodes, 
and  determine,  at  intervals  of  15  minutes,  the  contractions 
which  result  from  the  application  of  the  same  stimulus  as 
before ;  or  determine  the  position  of  the  secondary  coil  for  a 
minimum  stimulus. 

It  will  be  found  that  the  effect  of  the  section  is  first  to  in- 
crease, and  afterwards  to  diminish,  the  irritability  of  the 
portions  of  the  nerve  lying  immediately  below  the  section. 

In  the  above  observations,  the  student  must  make  sure  that 
the  electrodes  are  exactly  similar,  so  that  the  differences  which 
come  out  are  not  due  to  an}-  differences  of  resistance  in  the 
two  pair  of  electrodes  or  to  the  electrodes  of  one  pair  being 
further  apart  from  each  other  than  those  of  the  other,  etc. 

For  this  purpose  it  will  be  as  well,  after  a  series  of  observa- 
tions, to  exchange  the  electrodes,  putting  the  one  pair  in  the 
former  position  of  the  other,  and  repeat  the  series. 

Obs.  XVII.  On  the  sciatic  nerve  of  a  frog  in  which  the 
brain  and  spinal  cord  have  been  destroyed,  and  the  heart 
removed  so  as  to  stop  the  circulation,  place  three  pair  of 
electrodes,  one  near  the  gastrocnemius,  another  close  to  the 
central  end  of  the  nerve,  and  a  third  between  the  other  two. 
Divide  the  nerve  above  the  upper  pair. 

Arrange  the  preparation   carefully  in  the  moist  chamber. 


BY    DR.    MICHAEL    FOSTER.  393 

Send  a  single  weak  induction  shock  through  each  pair  of 
electrodes,  and  record  the  contraction ;  or  determine  the 
minimum  stimulus  for  each  pair  of  electrodes. 

Repeat  the  observation  at  intervals  during  the  day. 

It  will  be  found  that  after  the  temporary  increase  due  to 
section,  the  irritabilit}'  gradually  diminishes  from  the  central 
cut  end  towards  the  periphery,  the  extreme  muscular  branches 
being  the  last  to  die. 

Be  careful  that  no  part  of  the  nerve  is  more  exposed  than 
others. 

Obs.  XVIII.  Repeat  the  observation  in  a  frog  whose  brain 
and  spinal  cord  have  been  destroyed,  but  the  blood  current 
not  interfered  with. 

The  irritability  will  disappear  much  more  slowly,  but  in  the 
same  centrifugal  manner. 


CHAPTER  XXIX. 
PHENOMENA  ACCOMPANYING  A  NERVOUS  IMPULSE. 

The  only  phenomenon  definitely  and  certainly  known  to 
accompany  the  passage  of  a  nervous  impulse  is  the  negative 
variation  of  the  nerve  current  (see  Chap.  XXVI.,  sec.  II.). 

in  the  case  of  muscle,  the  negative  variation  shown  in  teta- 
nus by  the  galvanometer  was  proved  by  the  rheoscopic  frog  to 
consist  of  a  series  of  successive  negative  variations  (see  Chap. 
XXIV.,  sec.  III.). 

At  first  sight  a  similar  proof  seems  to  be  afforded  by  the  be- 
havior of  nerves. 

Obs.  I.  Prepare  a  nerve-muscle,  and  also  a  separate  piece  of 
nerve  as  long  as  possible.  Place  the  nerve-muscle  B  (fig.  291) 
on  a  glass  plate  ;  place  the  nerve  A  over  the  nerve  of  B,  in  either 
of  the  positions  shown  in  fig.  291, 1.  II. ;  connect  the  end  of  A 
with  an  induction  coil. 

A  single  shock  sent  through  A  will  produce  a  contraction  in 
b;  an  interrupted  current  will  throw  b  into  tetanus. 

Obs.  II.  Ligature  A  between  the  electrodes  and  the  end  touch- 
ing b.  No  contractions  will  appear  in  B  on  sending  shocks 
through  the  electrodes.  This  proves  that  the  results  of  Obs. 
I.  were  not  due  to  any  simple  electrical  conduction  through  a 
or  to  any  escape  of  the  current  to  B  by  other  means. 

The  same  thing  is  shown  in  the  so-called  "paradoxical  con- 
traction." 

Obs.  III.  In  the  leg  of  a  frog,  the  sciatic  nerve  divides  at  the 


394      PHENOMENA    ACCOMPANYING    A    NERVOUS    IMPULSE. 

lower  end  of  the  thigh  into  the  peroneal  and  tibial  branches. 
Dissect  out  one,  say  the  peroneal,  and  divide  it  at  its  periphery; 
Divide  the  sciatic  trunk  high  up,  and  place  the  peroneal  branch 
on  the  electrodes  of  an  induction  coil.  This  will  virtually  con- 
vert the  leg  into  a  preparation  similar  to  fig.  201,  III.;  the 
peroneal  and  tibial  branches  running,  so  to  speak,  side  by  side 
in  the  sciatic  trunk. 

Irritating  the  peroneal  nerve  A,  with  an  interrupted  current, 
will  produce  contractions  in  the  muscles  to  which  the  tibial  b 
is  distributed. 

All  these  "secondai^  contractions"  cease  when  the  nerve  a 
is  ligatured  between  the  electrodes  and  the  nerve  b. 

With  each  making  (competent  to  give  rise  to  a  nervous  im- 
pulse) of  the  exciting  current  through  a,  two  events  take  place 
which  must  be  kept  distinct  in  the  mind  of  the  student. 

First,  there  is  the  electrotonic  increase  (in  the  anelectrotonic 
region)  or  decrease  (in  the  katelectrotonic  region)  of  the 
natural  nerve  current.  This  increase  or  decrease  remains 
during  the  whole  time  of  the  passage  of  the  exciting  current, 
and  disappears  with  the  breaking. 

Secondly,  there  is  the  negative  variation  of  the  natural  cur- 
rent which  travels  with  the  nervous  impulse  indifferently  in 
either  direction,  and  which,  in  any  given  point  of  the  nerve,  is 
over  and  gone  in  an  exceedingly  short  time  after  the  act  of 
making  the  exciting  current. 

During  the  time  of  the  passage  of  the  (uniformly  constant) 
current,  there  is  no  negative  variation,  as  there  is  no  nervous 
impulse. 

On  breaking  the  exciting  current,  a  fresh  negative  variation 
sweeps  along  the  nerve,  if  the  current  is  of  such  a  character 
that  the  breaking  of  it  gives  rise  to  a  nervous  impulse. 

With  a  single  induction  shock  there  is  also  the  double  event 
of  a  negative  variation,  and,  as  well,  of  a  momentary  electro- 
tonus  ;  with  an  interrupted  current  there  is  a  succession  of 
such  double  events. 

In  both  these  cases  the  secondary  contraction,  as  in  Obs.  I., 
II.,  III.,  may  be  due  to  either  half  of  the  double  event:  to  the 
negative  variation,  or  to  the  electrotonic  change;  or  to  both. 
To  which  of  them  it  is  really  due  cannot  be  decided  by  the  use 
of  such  currents  only. 

If,  however,  the  electrotonic  increase  is  itself  competent  to 
cause  a  secondary  contraction,  the  contraction  ought  to  be  ob- 
tainable at  any  period  during  the  passage  of  an  exciting  con- 
stant current,  at  a  time  when  the  negative  variation  is  absent. 

Obs.  IV.  Connect  a  (placed  on  a  glass  plate)  with  a  constant 
current  of  two  cells,  the  positive  pole  towards  the  long  free  end  ; 
suspend  the  nerve  of  B  in  such  a  manner  over  A  that,  when  de- 
sired, it  can  be  let  fall  so  as  to  lie  upon  a  in  the  position  I.  or 
II.  (fig.  291). 


BY    DR.    MICHAEL    FOSTER.  395 

The  exciting  current  being  made,  a  negative  variation  sweeps 
over  A  and  is  gone.  There  remains,  however  the  anelectrotonic 
increase  of  the  natural  current  of  a  along  the  whole  region  from 
the  positive  pole  to  the  free  end.  Now  let  fall  b  as  directed. 
A  contraction  in  the  muscle  of  b  will  follow. 

This  can  only  be  due  to  theelectrotonically  increased  natural 
nerve  current  of  a  acting  as  a  stimulus  to  the  nerve  of  b  when 
the  circuit  is  closed  by  a  portion  of  b,  and  so  causing  a  nervous 
impulse  just  as  the  closing  of  any  other  galvanic  current 
would. 

And  inasmuch  as  the  electric  intensity  of  the  electrotonic 
increase  (or  decrease)  is  much  greater  than  that  of  the  negative 
variation,  the  secondary  contractions  in  the  Obs.  I.,  II.,  III. 
are  chiefly  due  to  this  cause. 


CHAPTER  XXX. 

VARIOUS    FORMS    OF    STIMULATION    OF    MUSCLE    AND 

NERVE. 

I.  Mechanical  Stimulation. — A  blow,  sufficient^  strong 
and  sudden,  applied  to  either  muscle  or  nerve,  will  produce  a 
contraction  ;  and  a  series  of  such  blows  repeated  sufficiently 
rapidly  will  produce  a  tetanus. 

This  may  be  roughly  shown  by  striking  simply  b}^  hand, 
with  some  thin  but  blunt  instrument,  either  muscle  or  nerve. 

For  more  exact  purposes,  the  tetanomotor  of  Heidenhain  may 
be  used,  and  can  be  applied  equally  to  muscle  or  nerve.  For  a 
description,  see.  Rosenthal,  Electrieitatslehre,  p.  116. 

A  simpler  method  is  that  of  Marey's,  with  a  tuning-fork. 

Obs.  I.  Get  ready  a  nerve-muscle  preparation.  Place  the 
nerve  on  a  small  piece  of  India-rubber  sheeting  stretched  quite 
tight  over  a  ring  of  wood  or  metal.  The  object  of  the  elastic 
India-rubber  is  to  soften  the  violence  of  the'  blows  given.  Ar- 
range a  tuning-fork  on  a  stand,  in  such  a  position  that  the 
vibrations  of  the  tuning-fork  shall  take  place  at  right  angles  to 
the  nerve.  Set  the  fork  going,  and  bring  it  in  slight  contact 
with  the  nerve.  The  muscle  will  at  once  be  thrown  into  teta- 
nus, which  may  be  recorded  on  the  cylinder. 

Obs.  1 1.  A  muscle  (gastrocnemius,  or,  better,  one  of  the  recti) 
of  a  frog  poisoned  with  urari,  may  be  placed  on  the  caoutchouc 
in  place  of  the  nerve. 

Tetanus  will  be  then  obtained  by  direct  mechanical  irritation 
of  the  muscle  itself,  without  intervention  of  the  nerves. 


396  VARIOUS   FORMS   OF   STIMULATION. 

II.  Idio-Muscular  Contractions. —  06s.  III.    Place  on 

some  flat  surface  a  nerve-muscle  preparation  which  has  heeu 
much  exhausted  by  treatment  or  by  long  removal  from  the 
body. 

Strike  the  muscle  sharply  with  some  thin  but  blunt  instru- 
ment (handle  of  scalpel),  across  the  middle  of  the  bell}',  at 
right  angles  to  its  long  axis. 

A  contraction  will  probably  follow — a  contraction  which,  as 
usual,  travels  along  the  whole  length  of  the  fibres. 

When  the  contraction,  however,  has  passed  awa}',  the  line 
where  the  blow  fell  will  be  marked  by  a  wheal,  i.  e.,  by  a  local 
shortening  and  thickening,  which  lasts  for  several  seconds,  but 
finally  disappears.  This  wheal,  this  local  thickening  and  short- 
ening, is  the  idio-muscular  contraction. 

Obn.  IV.  Wait  till  neither  muscle  nor  nerve  give  any  (ordi- 
nary) contraction  with  an  electric  stimulus.  Strike  as  before; 
the  idio-muscular  contraction  will  still  make  its  appearance. 
The  relaxation  becomes  slower  the  nearer  the  advent  of  rigor 
mortis,  with  the  onset  of  which  the  idio-muscular  contraction 
disappears. 

III.  Chemical  Stimulation  of  Muscle. — 06s.  V.  Care- 
fully dissect  out  the  sartorius  muscle  in  the  front  of  the  thigh 
(fig.  278  .s),  injuring  it  as  little  as  possible,  and  taking  away 
with  it  a  piece  of  the  pelvis  from  which  it  has  its  origin.  Clamp 
the  piece  of  pelvis,  avoiding  any  entanglement  of  the  fibres  of 
the  sartorius  itself,  and  attach  the  clamp  to  a  stand  so  that  the 
muscle  hangs  vertical.  If  it  be  desired  to  record  the  contrac- 
tions, thrust  a  fine  needle  through  the  middle  of  the  muscle, 
and  either  bring  the  muscle  to  bear  directly  on  the  recording 
surface,  steadying  it  with  a  shotted  thread  as  in  the  kymo- 
graphion  (Chap.  XVI.,  §  33),  or  make  the  needle  part  of  a 
delicate  lever.  With  a  sharp  pair  of  scissors,  cut  off  the  ten- 
don of  insertion  so  as  to  lay  bare  a  transverse  section  of  mus- 
cular fibre. 

Place  a  drop  of  any  or  each  of  the  below-mentioned  fluids  on 
a  rather  greasy  glass  plate  (so  as  to  have  a  good  convex  sur- 
face of  fluid),  and  very  gradually  raise  the  plate  until  the  fluid 
comes  in  contact  with  the  muscular  surface.  Immediately,  or 
very  shortly  after  contact,  spasmodic  contractions  of  the 
muscle  will  begin. 

The  following  substances  applied  directly  to  muscular  fibres 
produce  contractions: — 

Mineral  acids,  even  when  extremel}'  diluted;  solutions  of 
metallic  salts  ;  strong  solutions  of  neutral  salts  of  the  alkalies  ; 
lactic  acid  ;  glycerin,  even  diluted  to  a  considerable  extent. 

Obs.  VI.  The  vapor  of  ammonia,  even  in  mere  traces,  acts  as 
a  powerful  stimulus.  Place  a  few  drops  of  ammonia  in  a  small, 
flat,  wide-mouthed  bottle ;  cover  the  top  with  a  greased  glass 
plate.     Protect  the  muscle  from  all  extraneous  vapor  of  am- 


BY    DR.    MICHAEL    FOSTER.  397 

monia,  and  bring  the  closed  bottle  immediately  under  it.  The 
muscle  exhibiting  no  contractions  (there  being  no  escape  of 
ammonia),  slip  away  the  glass  cover  from  the  top  of  the  bottle  ; 
contractions  will  at  once  follow. 

In  the  above  observations,  a  fresh  surface  of  muscle  must  be 
cut  after  each  trial,  as  the  body  used  as  stimulus  destroys  the 
layer  of  muscle  with  which  it  is  immediately  in  contact. 

Apply  the  substance  under  trial  as  soon  as  possible  after 
making  the  section,  as  the  surface  exposed  soon  dies. 

IV.  Chemical  Stimulation  of  Nerve.— Obs.  VII.  Pre- 
pare a  nerve-muscle  with  as  long  a  piece  of  nerve  as  possible. 
Fasten  the  muscle  in  the  clamp,  and  support  the  nerve  so  that 
the  end  hangs  freely  down  in  a  vertical  position.  Bring  a  drop 
of  one  of  the  below-mentioned  fluids,  on  a  glass  plate,  in  con- 
tact with  the  end  of  the  nerve,  allow  some  millimetres  at  least 
of  the  nerves  to  be  fully  immersed  in  the  fluid  ;  and  either  take 
a  fresh  nerve-muscle  for  each  experiment  or  cut  away  each 
time  all  that  portion  of  the  nerve  which  had  been  previously 
exposed  to  the  action  of  the  fluid. 

The  movements  of  the  muscle  may  be  recorded  as  usual. 
Do  not  load  the  muscle  with  anything  more  than  the  lever 
itself. 

The  following  substances  applied  to  a  nerve  produce  con- 
tractions in  its  muscles: — 

Mineral  acids,  in  considerable  concentration  only  ;  neutral 
salts  of  the  alkalis  and  metallic  salts,  in  considerable  concen- 
tration only;  lactic  acid,  only  when  concentrated;  glycerin, 
only  when  concentrated. 

Ammonia  hardly  acts  at  all  as  a  stimulus  to  nerve;  in 
making  trial  with  this,  care  must  be  taken  to  protect  the 
muscle  from  all  ammonia  vapor. 

V.  Thermal  Stimulation  of  Muscle.— 06s.  VIII.  Hav- 
ing arranged  a  sartorious  muscle,  as  in  Obs.  V.,  bring  to  the 
lower  cut  surface  a  thin  slip  of  heated  metal.  On  contact 
taking  place,  a  contraction  will  result.  In  this  case  the  heat 
is  applied  to  a  part  only  of  the  muscle. 

Obs.  IX.  Attach  a  gastrocnemius  to  a  lever  (either  with 
the  origin  of  the  muscle  downwards  and  the  tendon  upwards, 
or  in  the  ordinary  position  with  the  tendon  playing  round  a 
pulley)  in  such  a  way  that  the  whole  muscle  may  readil}'  be 
immersed  in  fluid.  Fig.  202  represents  a  convenient  arrange- 
ment for  this  and  other  purposes.  The  muscle  a  is  fastened 
to  the  clamp  e,  which  is  part  of  the  bent  holder  d.  This 
holder  moves  on  the  same  upright  as  the  lever  e.  The  tendon 
of  the  muscle  is  attached  by  the  thread  b  to  the  lever,  so  that 
its  contractions  pull  the  lever  down.  The  lever  is  counter- 
balanced by  weights  carried  over  a  pulley.  The  muscle  can 
thus  be  readily  immersed  in  or  withdrawn  from  any  fluid. 
Counterbalance  the  lever  with  10  or  15  grammes. 


398  INDEPENDENT    MUSCULAR    IRRITABILITY. 

Immerse  the  whole  of  the  muscle  in  a  small  vessel  filled  with 
normal  saline  solution,  and  around  the  small  vessel  place  a 
large  one,  through  which  send  a  stream  of  hot  water. 

By  means  of  a  thermometer,  ascertain  the  temperature  of 
the  saline  solution  close  to  the  muscle.  When  the  tempera- 
ture rises  to  38°-40°  C,  the  muscle  is  thrown  into  tetanus. 
In  this  case  the  temperature  of  the  whole  muscle  has  been 
raised  at  as  nearly  as  possible  the  same  time. 

Immediatel}'  that  tetanus  has  set  in,  withdraw  the  muscle 
from  the  saline  solution.  The  tetanus  will  speedily  pass  away, 
and  the  muscle  will  i*emain  alive  and  irritable. 

Repeat  the  observation,  but  allow  the  muscle  to  continue  at 
the  temperature  of  40°  for  about  two  minutes.  On  removing 
the  solution,  the  muscle  will  still  remain  in  a  state  of  tetanic 
contraction,  as  indicated  by  the  position  of  the  lever,  and 
from  that  contraction  no  relaxation  will  take  place.  No 
stimulus,  however  strong,  will  be  able  to  call  forth  any  further 
contraction.  The  reaction  of  the  muscle  will  be  found  to  be 
acid,  and  its  extensibility  diminished.  In  fact,  the  muscle  will 
be  found  to  have  passed  from  a  state  of  tetanus  into  a  state  of 
rigor  mortis. 

VI.  Thermal  Stimulation  of  Nerves. — Obs.  X.  Ar- 
range the  nerve-muscle  preparation  with  the  nerve  dependent 
as  in  Obs.  VII. 

Bring  a  hot  surface  to  bear  on  the  end  of  the  nerve,  or  dip 
the  end  of  the  nerve  into  a  hot  normal  saline  solution,  or  place 
the  end  of  the  nerve  in  a  small  quantity  of  the  normal  saline 
solution,  the  temperature  of  which  gradually  raise. 

In  all  cases  contractions  in  the  muscle  will  follow. 


CHAPTER  XXXI. 

URARI  POISONING  AND  INDEPENDENT  MUSCULAR 
IRRITABILITY. 

Obs.  I.  Introduce  beneath  the  skin  of  the  back  of  a  strong 
frog  a  drop  or  two  of  a  solution  of  urari.  (The  exact  strength 
of  the  solution  and  the  dose  required  will  depend  on  the  source 
from  which  the  urari  has  been  obtained.)  In  a  short  time  the 
frog  will  be  found  perfectly  motionless,  with  its  respiration 
arrested,  but  its  heart  still  beating. 

La}'  bare  the  sciatic  nerve  in  the  thigh,  slip  under  it  a  pair- 
of  electrodes  connected  with  an  induction  coil,  and  stimulate 
the  nerve  with  an  interrupted  current,  taking  care  that  there  is 


BY    DR.    MICHAEL    FOSTER.  399 

no  escape  of  the  current  into  the  surrounding  muscles.  This 
may  be  effected  by  slipping  under  the  electrodes  a  small  piece 
of  India-rnbber  sheeting. 

If  the  animal  has  been  thoroughly  poisoned,  no  contractions 
whatever  in  the  muscles  of  the  leg  will  follow  upon  the  appli- 
cation of  a  stimulus,  however  strong,  to  the  nerve.  If  con- 
tractions do  make  their  appearance,  the  poisoning  is  not  com- 
plete;  and  the  student  must  wait  or  inject  a  further  quantity 
of  the  poison. 

The  nerve  having  been  proved  to  be  insensible  to  stimuli, 
la}T  bare  any  of  the  muscles  of  the  leg  and  apply  the  electrodes 
directly  to  them.  Contractions  will  be  manifest  upon  the  ap- 
plication of  a  ver}r  slight  stimulus. 

The  effect  of  urari  is  to  destroy  {or  suspend)  the  irritability 
of  nerves  but  not  that  of  muscles. 

Obs.  II.  In  a  strong  frog  make  an  incision  through  the  skin 
between  the  ilium  and  coccyx  along  the  line  k,  wt,  fig.  266 
Cut  cautiously  through  the  ileo-coccygeal  muscle  (fig.  267  d) 
until  the  peritoneal  cavity  is  reached.  The  three  nerves  (fig. 
295,  7'  8'  9'),  which  go  to  form  the  sciatic  nerve,  will  come  into 
view  when  the  sides  of  the  wound  are  held  apart.  Very  cau- 
tiously, by  means  of  a  small  aneurism  needle,  pass  a  thread 
under  these  nerves,  putting  it  under  from  the  outside  and 
bringing  it  out  again  on  the  median  side.  Be  very  careful  not 
to  wound  the  bloodvessels. 

Repeat  the  same  process  on  the  other  side,  passing  the  same 
thread  under  the  nerves  of  that  side  too,  but  putting  it  in  at 
the  median  side  and  bringing  it  out  at  the  outside.  The  thread 
will  now  be  in  the  position  of  the  line  o  p  q  in  fig.  266,  with 
the  nerves  of  one  side  lying  over  it  between  o  and  p,  and  those 
of  the  other  side  over  it  between  p  and  q.  Tie  the  thread  very 
tightly  round  the  abdomen,  so  as  to  check  entirely  the  flow  of 
blood  to  the  lower  limbs.  All  this  may  be  done  under  a  slight 
dose  of  chloroform.  The  nerves  thus  form  the  only  means  of 
communication  between  the  hind  limbs  and  the  trunk,  the 
vascular  communication  being  entirely  stopped.  Now  inject 
a  small  quantity  of  urari  into  the  back,  and  wait  until  the 
poison  has  had  time  to  produce  its  effects  in  that  part  of  the 
body  to  which  alone  it  h:is  access,  viz.,  the  part  above  the  liga- 
ture. 

The  following  facts  may  then  be  determined  : — 

Though  there  are  no  voluntary  movements  in  the  body,  head, 
or  fore  limbs,  some  slight  (voluntary?)  movements  may  some- 
timefl  be  witnessed  in  the  hind  limbs. 

Pinching,  or  otherwise  stimulating,  either  hind  foot  may 
produce  movement*  in  either  one  or  both  hind  limbs,  but  in  no 
other  part  of  the  body. 

Pinching,  or  otherwise  stimulating,  the  skin  of  the  head, 


400  INDEPENDENT    MUSCULAR   IRRITABILITY. 

fore  limbs  or  trunk  above  tbe  ligature  may  produce  movements 
in  the  hind  limbs,  but  in  no  other  part  of  the  body. 

These  facts  are  intelligible  only  on  the  hypothesis  that  the 
urari  has  destroyed  (or  suspended)  the  irritability  of  the 
motor  nerves  in  that  part  of  the  body  to  which,  by  means  of 
the  blood  current,  it  has  had  access,  but  has  not  destroyed  the 
irritability  of  the  sensory  nerves  or  of  the  central  nervous  sys- 
tem. Pinching  the  skin  of  the  fore  limb  gave  rise  to  an  affe- 
rent nervous  impulse  which,  either  by  volition  or  by  reflex 
action,  gave  rise  in  turn  to  efferent  impulses  which  were  unable 
to  manifest  themselves  through  the  poisoned  motor  nerves  of 
the  fore  limbs  and  trunk,  but  found  vent  through  the  unpoisoned 
motor  nerves  of  the  hind  limbs. 

In  order  to  bring  these  results  out  well,  the  dose  of  poison 
must  not  be  more  than  sufficient  to  poison  the  motor  nerves. 
Subsequent  or  stronger  action  of  the  poison  affects  the  central 
nervous  system  as  well. 

Obs.  III.  In  a  fresh,  strong  frog,  lay  bare  the  sciatic  nerve 
on  one  side — say  the  right — in  its  lower  course,  place  a  ligature 
under  it  near  where  it  divides  into  its  two  branches,  and  tie  the 
ligature  tightly  round  the  leg  above  the  knee.  The  circulation 
of  the  lower  right  leg  will  thus  be  completely  arrested  ;  but  in- 
asmuch as  the  nerve  is  not  included  in  the  ligature,  there  will 
be  complete  nervous  connection  between  the  right  lower  leg  and 
the  rest  of  the  body.  Poison  with  urari.  As  soon  as  the 
animal  has  come  under  the  influence  of  the  poison,  determine 
the  following  facts  : — 

Complete  absence  of  spontaneous  movements,  except  per- 
haps some  feeble  stirring  of  the  right  lower  leg. 

Stimulation  of  the  right  lower  foot  may  produce  movements 
in  the  right  lower  leg,  but  will  not  produce  movements  in  any 
other  part  of  the  body. 

Stimulation  of  any  part  of  body  may  produce  movements  in 
the  right  lower  leg,  but  in  no  other  part  of  the  body. 

If  the  two  sciatic  nerves  be  laid  bare  along  their  whole 
course,  it  will  be  found  that  stimulation,  however  strong, 
applied  to  the  left  sciatic  nerve,  produces  no  contractions 
whatever  in  the  muscles  to  which  its  branches  go;  while 
stimulation,  even  slight,  of  the  right  sciatic  nerve,  whether 
applied  above  or  below  the  level  of  the  ligature,  and  even 
close  up  to  the  spinal  cord,  produces  contractions  in  the  mus- 
cles of  the  right  lower  leg,  but  in  none  other. 

Now  the  whole  of  the  trunk  of  the  right  sciatic  nerve,  being 
supplied  with  poisoned  blood,  has  been  as  much  subject  to  the 
influence  of  the  urari  as  the  left  sciatic.  Nevertheless,  while 
the  trunk  of  the  left  sciatic  seems  to  have  entirely  lost  its 
irritability,  that  of  the  right  seems  to  have  suffered  very  little 
indeed.     The  difference  really  is,  that  the  left  sciatic  trunk 


BY    DR.    MICHAEL   FOSTER.  401 

cannot  manifest  its  irritability  because  all  its  branches  are 
poisoned;  the  right  sciatic  can,  b}-  means  of  those  branches 
which  through  the  ligature  have  been  removed  from  the  in- 
fluence of  the  poison-bearing  blood. 

With  moderate  doses  of  urari,  the  small  branches  appear  to 
be  poisoned  and  to  have  lost  their  irritability,  ivhile  the  trunks 
are  still  intact. 

Obs.  IY.  In  a  fresh,  strong  frog,  dissect  out  a  gastrocne- 
mius (or  any  other  single  muscle),  dividing  both  insertion  and 
origin  and  ligaturing  its  bloodvessels,  thus  leaving  it  connected 
with  the  rest  of  the  bod}-  by  its  nerve  onty.  Poison  the  frog 
with  urari. 

It  will  be  found  that  stimulation  of  the  nerve  fibres  supply- 
ing the  muscle  at  any  part  of  their  course,  whether  close  to 
the  muscle,  or  in  the  sciatic  trunk  as  far  away  as  possible  from 
the  muscle,  will  produce  contractions  in  the  muscle,  though  all 
the  other  motor  nerves  in  the  bodjr  seem  to  have  lost  their 
irritability. 

In  a  similar  way  it  may  be  proved  that  if  only  the  portion 
of  nerve  immediately  next  to  the  muscle  be  kept  from  the  in- 
fluence of  the  poison,  however  much  the  rest  may  have  been 
subjected  to  the  action  of  the  poison,  the  muscle  may  be 
thrown  into  contractions  by  stimuli  applied  to  any  part  of  the 
course  of  the  nerve.  The  presumption  is,  that  urari  acts  on 
the  extreme  ends  only  of  the  nerve,  possibly  on  the  end-plates. 

Yet,  as  we  have  seen,  however  much  the  muscles  themselves 
be  exposed  to  the  action  of  the  poison,  they  do  not  lose  their 
irritability.  These  two  facts  (1),  that  urari  poisons  the  ex- 
treme peripheral  ends  of  the  nerves,  and  (2),  that  the  muscles 
themselves  do  not  under  urari  lose  their  irritabilit}',  form  to- 
gether a  very  strong  argument  for  the  view  that  muscles  pos- 
sess an  independent  irritability  of  their  own. 

06s.  Y.  Get  ready  a  nerve-muscle  preparation.  Place  one 
pair  of  electrodes  (A)  (as  far  apart  as  practicable)  on  the 
muscle  itself,  another  (B)  on  the  nerve  near  the  muscle,  and  a 
third  (non-polarizable)  pair  (C)  on  the  nerve  also,  a  little 
higher  up  than  B.  Connect  A  and  B  with  induction  coils, 
and  determine  the  minimum  stimulus  required  to  be  sent 
through  each  pair  of  electrodes  in  order  to  produce  a  contrac- 
tion in  the  muscle.  It  will  be  as  well  to  record  the  contraction 
by  means  of  the  lever,  etc.  The  irritability  of  the  nerve  (elec- 
trodes 15)  and  of  the  muscle  and  nerve  together  (electrodes  A) 
will  thus  be  respectively  determined. 

Now  pass  through  C  a  strong  ascending  constant  current ; 
and  while  the  current  is  passing,  determine  as  before  the  mini' 
mum  stimulus  for  A  mid  B.  By  the  ascending  constant  cur- 
rent  the  portion  of  nerve  between  the  electrodes  C  and  the 
muscle  has  been  thrown  into  a  state  of  anelectrotonus  ;  and  it 
26 


402      THE   FUNCTIONS   OF    THE   ROOTS   OF   SPINAL   NERVES. 

will  be  found  that  the  irritability  of  the  nerve  in  this  region 
has  been  very  considerably  lowered  ;  or,  if  the  polarizing  cur- 
rent be  strong  enough,  and  the  pair  of  polarizing  electrodes 
far  enough  apart,  has  been  suspended  altogether.  Contractions 
in  the  muscle  are  either  entirely  a'bsent  when  a  shock  is  sent 
through  B,  or  only  appear  when  the  shock  is  very  strong.  At 
the  same  time  it  will  be  found  that  the  minimum  stimulus  of 
A  is  not  very  different  from  what  it  was  before.  A  rather 
stronger  stimulus  is  required  to  produce  a  contraction,  but  the 
difference  is  strikingly  less  than  that  in  the  case  of  the  elec- 
trodes B,  and  even  this  difference  may  be  accounted  for  by 
considering  that  the  electrodes  A  stimulate  both  the  muscular 
fibres  and  the  intra-muscular  nerve  fibres,  and  that  the  com- 
bined effect  is  therefore  greater  when  the  intra-muscular  nerves 
are  intact  than  when  they  are  paralyzed  b}r  the  ascending  cur- 
rent. 

Thus  the  ascending  current  will,  if  strong  enough,  suspend 
the  irritability  of.  the  nerve  fibres  supplying  a  muscle,  and  yet 
will  leave  the  muscle  but  little  altered  in  its  susceptibility  to 
direct  stimulation.  This  again  is  an  argument  in  favor  of 
"  independent  muscular  irritability." 

The  same  view  is  supported  by  the  facts  that  the  chemical 
irritants  of  nerve  and  muscle  are  not  identical  (see  Chapter 
XXX.,  Obs.  V.-VII.)  ;  that  the  lower  part  of  the  sartorius 
of  young  frogs  in  which  no  nerve  fibres  can  be  detected,  is 
susceptible  of  chemical  stimulation  ;  and  that  the  idio-muscu- 
lar  contraction  may  be  called  forth  in  muscles  the  nerves  of 
which  have  completely  lost  their  irritability.  (Chapter  XXX., 
Obs.  IV.) 


CHAPTER  XXXII. 
THE  FUNCTIONS  OF  THE  ROOTS  OF  SPINAL  NERVES. 

The  posterior  root  of  a  spinal  nerve  is  said  to  be  sensory, 
i.  t?.,  to  serve  as  the  path  along  which  alone  centripetal  influ- 
ences pass  on  their  way  from  the  peripheral  nerve  terminations 
to  those  central  organs,  in  which  the3'  become  transformed 
into  sensations,  or  give  rise  to  reflex  actions,  etc.  The  anterior 
root  is  said  to  be  motor,  i.  e.,  to  serve  as  the  path  along  which 
alone  centrifugal  impulses  pass,  on  their  way  from  the  central 
organs  to  the  nerve  terminations  in  muscles,  etc.  The  truth 
of  this  absolute  distinction  in  function  between  the  two  roots 
may  readily  be  shown  in  the  frog. 

The  results  are  most  clear  and  distinct  when  the  organs  of 


BY    DR.    MICHAEL   FOSTER.  403 

consciousness  are  intact,  and  the  ordinary  tokens  of  sensation 
are  used  to  determine  whether  the  impulses  caused  by  stimu- 
lation of  the  peripheral  terminations  reach  the  conscious  cen- 
tral nervous  sj-stem  or  not.  But  the  facts  may  also  be  readily 
shown  in  the  absence  of  the  brain,  when  reflex  action  is  taken 
as  a  proof  of  a  centripetal  impulse  having  reached  the  spinal 
cord.  In  the  former  case,  the  frog  should  be  placed  under 
chloroform  during  the  laying  bare  of  the  roots.  In  the  latter 
the  medulla  should  be  previously  divided  in  the  neck  (see 
Chap.  XXXIII.). 

The  frog  being  placed  on  its  bell}',  make  an  incision  in  the 
middle  of  the  back,  from  the  upper  end  of  coccyx  to  the  level 
of  the  limbs,  see  fig.  26G  g  h.  Having  hooked  back  the  flaps 
of  skin,  carry  the  median  incision  down  to  the  spines  of  the 
vertebrae,  and  dissect  away  the  longitudinal  muscles  on  either 
side,  so  as  to  lay  bare  the  bony  arches,  and  then  hook  back 
the  muscles  on  either  side,  or  cut  them  away  altogether. 

With  a  small  but  strong  blunt-pointed  pair  of  scissors,  cut 
through,  on  either  side,  the  arch  of  the  last  (eighth)  vertebra 
(be  careful  not  to  thrust  the  scissors  in  too  deep),  and  remove 
the  piece  so  loosened.  Proceed  then  to  the  next  arch  above, 
and  so  remove  three  arches.  The  roots  of  the  nerves  will  be 
seen  lying  in  the  spinal  canal.  Snip  away  the  remains  of  the 
arches  on  each  side,  until  the  last  three  (or  four)  roots  are 
quite  clear,  being  very  careful  not  to  touch  the  nerves  with 
the  scissors.  The  bleeding  may  be  disregarded.  The  posterior 
roots  lie  superficialby,  are  large,  and  hide  the  anterior  roots. 
The  several  roots  may  be  separated  from  each  other  by  pass- 
ing with  great  care  the  blunt  seeker  lengthways  between  them. 

Very  gently  pass  a  fine  aneurism  needle,  armed  with  thin  silk 
(ex.  gr.,  a  fine  sewing-needle,  with  the  head  slightly  bent,  and 
the  point  fixed  in  a  handle),  under  a  conspicuous  posterior  root 
which  seems  to  be  the  last.  This  will  be  the  ninth  ;  the  tenth 
is  much  smaller,  and  runs  closer  to  the  filum  terminale,  see  fig. 
295.  The  seventh,  eighth,  and  ninth  form  the  ischiatic,  from 
which  the  crural,  Ne,  and  sciatic,  Ni,  nerves  are  given  off,  the 
seventh  supplying  most  of  the  fibres  of  the  crural.  Tie  the  silk 
loosely  round  the  nerve,  near  its  entrance  into  the  cord.  Care- 
fully avoid  compressing  the  nerve. 

068.  I.  The  frog  being  completely  at  rest,  draw  the  ligature 
tight,  observing  the  frog  all  the  while.  If  the  animal  be  in  good 
condition,  some  movements  will  be  visible  in  some  parts  of  the 
body  as  evidence  either  of  sensibility  or  reflex  action.  Xow  cut 
tin:  nerve  between  the  ligature  and  the  cord  ;  some  movement 
will  probably  be  again  witnessed. 

06*.  II.  Lift  the  peripheral  stump  of  the  nerve  carefully  up 
by  means  of  the  ligature,  and  slip  it  upon  the  curved  shielded 
electrodes  (fig.  271)  which  may  be  held  in  the  hand,  or,  better, 


404      THE    FUNCTIONS   OF    THE    ROOTS   OF   SPINAL   NEIIVES. 

fixed  on  a  movable  stand.  To  prevent  any  escape  of  the  cur- 
rent, slip  a  fragment  of  India-rubber  sheeting  beneath  the  nerve 
and  electrodes,  so  as  to  isolate  these  from  the  cord  and  from 
the  rest  of  the  nerves.  Pass  a  moderately  strong  interrupted 
current  through  the  electrodes.  If  there  be  no  escape  of  the 
current,  the  animal  will  not  move  in  the  slightest. 

Obs.  I'll.  Repeat  the  observation  with  the  nerve-root  next 
above  (the  8th),  with  this  difference;  place  the  ligature  as  near 
as  possible  to  the  walls  of  the  spinal  canal ;  divide  the  nerve 
between  the  ligature  and  the  wall,  and  place  the  central  instead 
of  the.peripheral  stump  on  the  electrodes. 

Ligature  and  section,  as  before,  produce  movements.  A 
very  moderate  interrupted  current  applied  to  the  central  stump 
will  produce  verj  considerable  movements  in  various  parts  of 
the  body,  i.  e.,  signs  of  sensation  or  reflex  action,  as  the  case 
may  be. 

Ligature  or  section  of  the  posterior  roots  of  spinal  nerves 
jiroduces  movements  in  various  p>arts  of  (he  body.  Stimulation 
of  the  peripheral  stump  produces  no  movement  whatever ;  stimu- 
lation of  the  central  stump  produces  considerable  movement*. 
These  movements, be  they  simple  re  flex  actions  or  more  compli- 
cated voluntary  movements  set  going  by  conscious  sensations,  are 
evidences  of  centripetal  sensor  impidses,  excited  in  the  posterior 
sensory  roots. 

Obs.  IV.  Examine  now  the  sensibility  of  the  hind  limb  on 
which  you  have  been  operating.  It  will  be  found  that  pinching 
the  toes  or  the  skin  of  the  hind  surfaces  of  the  limb  produces 
little  or  no  reflex  action.  The  anterior  surface  of  the  leg,  how- 
ever, still  retains  considerable  sensibilit}'. 

Obs.  V.  Divide  the  posterior  roots  of  the  7th  and  8th  nerves, 
and  also  that  of  the  small  10th  nerve.  The  whole  limb  will 
now  be  found  to  be  totally  insensible.  Movements  of  the  leg, 
however,  may  readily  be  called  forth  by  pinching  the  skin  of 
the  back,  or  any  other  part  of  the  body  except  the  leg  itself. 

Division  of  the  posterior  roots  stops  the  passage  of  sensory,  but 
not  of  motor  impidses. 

Obs.  VI.  Carefully  cut  away  the  posterior  roots  on  which  you 
have  been  experimenting.  The  anterior  roots,  which  are  thin- 
ner than  the  posterior,  will  now  come  into  view. 

Repeat  on  one  of  these  anterior  roots  (9th  nerve)  Obs.  II. 
Mere  touching  the  nerve  will  probably  produce  a  movement  of 
the  hind  limb  of  that  side.  This  result  will  at  all  events  follow 
upon  ligature  and  section. 

Stimulation  of  the  peripheral  stump,  with  even  a  very  feeble 
stimulus,  will  produce  tetanus  in  the  limb. 

Obs.  VII.  Repeat  on  the  anterior  root  next  above  Obs.  III. 

No  effect  whatever  will  be  produced  by  stimulating  the  cen- 
tral stump. 


BY    DR.    MICHAEL    FOSTER.  405 

The  anterior  roots  convey  motor  impulses  centrifugally,  but 
not  senso7~y  impulses  centripetally. 

Obs.  VIII.  In  a  fresh,  strong  frog  lay  bare  the  roots  of  the 
spinal  nerves  and  divide  the  posterior  roots  of  the  7th,  8th,  9th, 
10th  nerves  on  the  right  side  and  the  corresponding  anterior 
roots  on  the  left  side. 

The  left  leg  will  remain  motionless,  being  simply  dragged 
along  by  the  rest  of  the  bod}*,  but  never  moving  of  itself.  [If 
the  brain  has  been  previously  destroyed  or  separated  from  the 
spinal  cord,  the  right  leg  will  be  drawn  up  as  usual  (see  Chap. 
XXXIII.),  but  not  the  feft  leg.] 

Pinching  the  right  foot,  or  otherwise  irritating  the  right  leg, 
will  give  rise  to  no  movement  whatever  in  any  part  of  the  body, 
will  call  forth  no  signs  of  sensation. 

Pinching  the  left  foot,  or  otherwise  irritating  the  left  leg,  or 
an}'  part  of  the  body  except  the  right  leg,  will  produce  move- 
ments which  ma}'  occur  in  any  part  of  the  body  except  the  left 
leg  itself. 

In  this  case  the  right  leg  has  had  all  its  posterior,  the  left  all 
its  anterior,  roots  divided.  No  centripetal  impulses  pass  up 
from  the  right  leg  to  the  central  nervous  system  ;  no  centrifugal 
impulses  pass  down  from  the  central  nervous  system  to  muscles 
of  the  left  leg. 

The  posterior  i-oots  are  the  channels  of  the  centripetal  (sen- 
sory), the  anterior  of  centrifugal  (motor)  impulses. 

Recurrent  Sensibility. — This  is  never  witnessed  in  the 
frog.  It  can  only  be  shown  in  the  higher  animals,  the  cat  or 
dog  being  best  adapted  for  the  purpose.  The  method  adopted 
is  very  similar  to  the  above — the  arches  of  one  or  two  verte- 
brae being  carefully  sawn  through  or  cut  through  with  the  bone 
forceps,  and  the  exposed  roots  being  very  carefully  freed  from 
the  connective  tissue  surrounding  them.  If  the  animal  be 
strong,  and  have  thoroughly  recovered  from  the  chloroform 
and  from  the  operation,  irritation  of  the  peripheral  stump  of 
the  anterior  root  causes  not  only  contractions  in  the  muscles 
supplied  by  the  nerve,  but  also  movements  in  other  parts  of 
the  body  indicative  of  pain  or  of  sensations.  On  dividing  the 
mixed  trunk  at  some  little  distance  from  the  junction  of  the 
roots,  the  contractions  of  the  muscles  supplied  by  the  nerve 
cease,  but  the  general  signs  of  pain  or  of  sensation  still  re- 
main. These  disappear  when  the  posterior  root  is  also  divided. 
Hence  it  is  inferred  that  fibres  conveying  centripetal  impulses 
pass  downward  along  the  anterior  root  to  the  mixed  trunk, 
and  thence,  turning  round,  run  back  again  to  the  central  ner- 
vous organ  along  the  posterior  root.  (For  further  details,  see 
Iicrnard,  Lecons  sur  la  Phys.  clu  Systeme  Nervcux,  Vol.  I., 
p.  02  et  seq.) 


40G  REFLEX    ACTIONS. 


CHAPTER  XXXIII. 

KEFLEX  ACTIONS. 

Reflex  actions  are  best  studied  in  the  frog,  the  brain  hav- 
ing first  been  removed,  or  at  least  separated  from  the  spinal 
cord.  The  strongest  and  healthiest  frogs  should  be  chosen  for 
the  purpose.  The  student  should  make  himself  acquainted 
with  the  general  form  of  the  dried  frog's  skull.  This  having 
been  done,  the  position  of  the  occipito-atlantal  articulation 
may  readily  be  recognized  on  the  living  animal. 

Division  of  the  Medulla  Oblongata. — Having  wrapped  a  cloth 
round  the  hind  legs  and  body  of  the  animal,  clasp  the  fore  legs 
round  the  ring  finger  of  the  left  hand,  and  hold  them  in  posi- 
tion by  the  middle  and  little  fingers,  which  should  also  hold 
tight  the  cloth.  Press  down  the  tip  of  the  frog's  nose  with  the 
thumb  of  the  same  hand,  so  as  to  bend  the  neck  as  much  as 
possible.  If  the  fore-finger  of  the  right  hand  be  now  made  to 
glide  over  the  roof  of  the  skull,  exactly  in  the  mid-line  from 
before  backwards,  a  slight  but  distinct  depression  will  be  felt 
in  the  neck  at  the  point  where  the  occiput  ends,  and  where  the 
medulla  is  covered,  not  by  bone,  but  by  the  occipito-atlantal 
membrane.  It  lies  in  a  line  drawn  across  the  skull  at  a  tan- 
gent to  the  hinder  borders  of  the  two  membrana  tympani.  (Fig. 
266,  line  a-b.) 

The  position  of  this  point  being  satisfactorily  ascertained, 
with  a  sharp-pointed  scalpel  make  a  small  transverse  incision 
across  it  about  a  few  millimetres  long.  The  incision  should 
not  be  carried  too  far  on  either  side.  If  the  blood,  which  comes 
freely,  be  rapidly  taken  up  with  a  sponge,  and  the  neck  be  kept 
well  bent,  the  medulla  will  be  clearly  seen.  This  should  now 
be  completely  cut  across,  and  the  wound  be  rapidly  sponged, 
in  order  that  the  division  ma3T  be  ascertained  by  actual  inspec- 
tion to  be  complete.  The  encephalon  may  then  be  completely 
destroyed  by  introducing  a  blunt  piece  of  wire  into  the  wound, 
and  eviscerating  the  skull.  If  the  wound  be  then  left  to  itself 
the  bleeding  will,  in  most  cases,  soon  cease  ;  if  not,  a  small  plug 
of  wood  (the  sharpened  end  of  a  lucifer  match)  ma}'  be  thrust 
into  the  skull.  This,  however,  should  be  avoided  if  possible. 
It  is  better  to  conduct  the  operation  in  this  way,  seeing  clearly 
what  is  being  done,  than  to  divide  skin,  membrane,  and  medulla 
by  one  thrust,  without  being  able  to  tell  exactly  whether  the 
division  is  complete. 


BY    DR.    MICHAEL    FOSTER.  407 

Decapitation. — Introduce  one  blade  of  a  strong  pair  of 
scissors  into  the  mouth,  and  bring  it,  transverse  to  the  long 
axis  of  the  head,  as  far  back  as  possible.  Bring  the  other 
blade  down  to  the  skin  behind  the  occiput,  and  quickly  cut  off 
the  head,  being  careful  that  neither  blade  slips  forward. 
Simple  inspection  will,  at  once,  determine  whether  the  whole 
of  the  encephalon  has  been  removed  or  no.  The  bleeding,  in 
man}'  cases,  is  excessive,  and  must  be  staunched  by  astringents 
or  by  the  actual  cautery.  Indeed,  where  decapitation  seems 
desirable,  it  is  far  better  to  employ  the  galvanic  cauture, 
introducing  the  loop  of  platinum  wire  into  the  mouth,  and 
bringing  it  out  through  the  occiput  along  the  line  a-&,  fig.  266. 

For  the  general  study  of  reflex  actions,  division  of  the 
medulla  is  preferable  to  decapitation.  The  large  amount  of 
bleeding,  the  exposure  to  the  air,  and  possibly  other  causes, 
often  lead,  in  the  latter  case,  to  abnormal  results,  ex.  gr., 
pseudo-voluntary  movements  on  the  one  hand,  and  lack  of 
reaction  on  the  other. 

Obs.  I.  Place  the  frog,  immediately  after  the  division  of 
the  medulla,  on  its  belby,  with  its  legs  extended.  In  most 
cases  the  legs  will  remain  extended,  and  at  first  no  movements 
will  be  produced  by  stimuli  applied  to  any  part  of  the  body. 
The  animal  (or  rather  its  spinal  cord)  is  in  a  state  of  shock, 
consecpuent  upon  the  operation. 

If  the  animal  be  watched,  it  will  be  found  that  after  a  while 
the  hind  legs,  apparently  without  the  intervention  of  any 
external  stimulus,  are  suddenly,  first  one  and  then  the  other, 
drawn  up  to  the  body,  and  assume  the  wonted  flexed  posture. 
This  is  a  token  that  the  condition  of  shock  has  passed  away. 
If  now  one  of  the  legs  be  pulled  out,  and  then  let  go  again,  it 
will  be  immediately  drawn  up  once  more  under  the  bod}r. 

After  the  shock  has  passed  away,  the  legs  having  been 
drawn  up,  the  animal  will  appear  to  have  assumed  a  natural 
posture.  On  observing  it  more  closety,  however,  it  will  be 
found  that  the  posture  is  not  quite  natural.  The  line  of  the 
back  is  too  horizontal,  the  head  lies  flat,  with  the  neck  almost 
touching  the  table,  and  the  fore  limbs  spread  out;  whereas  an 
entire  frog  keeps  the  head  and  neck  raised  high  up  on  the 
almost  vertical  fore  limbs,  and  the  line  of  the  body  makes  a 
large  angle  with  the  plane  of  the  table. 

If  left  to  itself,  the  frog  will  exhibit  no  movements  whatever, 
will  not  stir  from  the  spot  in  which  it  is  placed  unless  sbme 
external  stimulus  be  brought  to  bear  upon  it.  This  absence 
of  spontaneous  movements  is  most  marked,  when  sudden 
variations  of  temperature  are  avoided,  and  the  skin  is  not 
allowed  to  get  dry.  Eence  it  is  advisable  to  place  the  animal 
on  ;i  dish  containing  a  small  quantity  of  water,  and  to  cover  it 
with  a  glass  shade. 


408  REFLEX    ACTIONS. 

If  turned  over  and  placed  on  its  back,  it  remains  for  an 
indefinite  period  in  that  position,  without  making  any  attempt 
to  regain  its  natural  posture.  While  on  its  back,  the  heart 
may  be  observed  beating,  but  the  respiratory  movements  will 
be  wholly  absent. 

If  thrown  into  a  basin  of  water,  it  will  sink  to  the  bottom 
like  a  lump  of  lead  (unless  the  lungs  be  too  much  distended 
with  air),  without  making  any  attempt  whatever  to  swim. 

15y  irritating  it  in  various  ways,  it  may  be  made  to  execute 
a  variety  of  movements  (see  following  observations),  but  can- 
not, by  any  means,  be  made  to  leap  or  spring  forward. 

Obs.  II.  With  the  point  of  a  needle  gently  stroke  the 
abdominal  walls  on  one  side.  A  slight  twitching  of  the 
muscles  of  the  region  so  stroked  will  be  witnessed.  This  is 
one  of  the  simplest  forms  of  reflex  action.  Contraction  takes 
place  in  muscles  on  that  side  of  the  body  only,  the  afferent 
nerves  of  which  are  affected  by  the  stimulus,  and  it  will  be 
found  that  the  afferent  and  efferent  nerves  concerned  in  the 
action  belong  tolerably  exactly  to  the  same  segment  of  the 
spinal  cord. 

On  increasing  the  stimulus  gradually  by  stroking  more 
forcibly,  the  twitchhigs  will  be  seen  to  spread  over  a  wider 
and  wider  area,  to  invade  the  other  side,  and  finall}'  to  pass 
into  the  hinder  and  fore  limbs. 

With  a  stimulus,  sufficiently  slight,  of  an  afferent  nerve,  a 
definite  small  group  of  efferent  fibres  are  alone  affected  by 
reflex  action.  On  increasing  the  intensity  of  the  stimulus,  the 
effect  spreads  into  a  larger  and  larger  number  of  efferent  fibres. 

Obs.  III.  Pass  an  S  hook  through  the  lower  jaw,  and  thus 
suspend  the  animal  on  a  suitable  upright,  with  the  legs  and 
body  hanging  freely  down. 

Or,  take  a  piece  of  thin  wood,  about  an  inch  broad  and  five 
long ;  place  the  frog,  belly  downwards,  on  it,  in  such  a  wa}r 
that  the  wood  reaches  no  farther  down  than  the  lower  part  of 
the  abdomen,  and  secure  the  frog  to  it  by  two  slight  India- 
rubber  bands,  one  immediately  below  the  fore  limbs,  and  the 
other  a  little  above  the  thighs.  If  the  wooden  slip  be  now 
fastened  vertically  in  an  upright,  the  hind  limbs  will  hang 
freely  down,  completely  loose,  while  the  body  will  be  held 
sufficiently  firm. 

For  most  purposes  the  former  simpler  method  is  sufficient. 
When  it  is  desired  to  study  the  movements  of  the  legs  alone 
with  some  accuracy,  the  latter  method  must  be  adopted. 

The  legs  hanging  freely  down,  and  the  bod}'  being  com- 
pletely at  rest,  with  a  smooth  pair  of  forceps  gentl}-  pinch  the 
tip  of  one  of  the  toes.  The  leg  will  immediateljr  be  drawn 
sharply  up,  and  after  being  kept  in  the  flexed  position  for  a 
variable  time,  will  be  slowly  dropped  again. 


BY    DR.    MICHAEL    FOSTER.  409 

Repeat  the  observation  on  the  other  leg.  Only  that  leg,  the 
toes  of  which  are  pinched,  is  drawn  up :  and  if  the  toes  be  not 
too  roughly  treated,  no  other  movement  than  the  drawing  up 
of  the  leg  is  witnessed. 

Obs.  IV.  With  more  force  pinch  the  folds  of  the  skin  around 
the  anus.  Both  legs  will  be  suddenly  complete^'  drawn  up, 
so  that  the  toes  of  both  feet  are  brought  above  the  forceps,  and 
are  then  as  suddenly  and  completely  extended  again.  This 
movement  of  sudden  flexion  and  extension,  that  is  of  kicking, 
may  be  repeated  rapidly  several  times  as  the  result  of  one  for- 
cible pinching  of  the  region  in  question. 

Obs.  V.  Pinch  with  some  force  the  skin  at  a  point  on  one 
side  of  the  loins.  The  leg  of  the  same  side  will  be  suddenly 
flexed  over  the  back,  and  brought  round  back  again  with  a 
sweeping  movement. 

Obs.  VI.  The  hind  limbs  hanging  down  as  before,  place  a 
watch  or  other  small  glass  containing  very  dilute  sulphuric 
acid  (one  drop  to  20,  30,  or  50  CCm,  strong  enough  to  give  an 
acid  taste)  underneath  the  frog,  and  bring  it  close  up  to  one 
of  the  feet,  so  that  the  extreme  tip  of  the  longest  toe  just  dips 
into  the  acid.  Within  a  short  time,  the  exact  length  of  time 
being  determined  by  the  strength  of  the  acid  and  the  condition 
of  the  frog,  the  leg  will  be  flexed,  and  the  foot  withdrawn. 
Very  frequently  the  movement,  even  after  the  fluid  has  been 
taken  quite  out  of  the  wa}',  is  not  confined  to  a  single  flexion 
followed  by  a  relaxation,  but  consists  of  a  series  of  flexions 
and  relaxations,  each  succeeding  flexion  being  less  marked  than 
its  predecessor. 

Repeat  the  observation  with  varying  degrees  of  acidity, 
beginning  with  simple  distilled  water,  and  gradually  adding 
acid.  Be  careful  to  wash  the  foot  carefully  with  water  after 
each  observation,  to  wait  some  minutes  between  each  applica- 
tion, and  to  dip  only  the  tip  of  the  toe,  and  that  to  the  same 
extent  in  each  case. 

.Measure  by  means  of  a  metronome,  beating  very  rapidly,  the 
exact  time  intervening  between  the  actual  entrance  of  the  toe 
into  the  fluid,  and  its  withdrawal. 

With  an  acid  of  a  given  strength,  applied  to  the  same  frog 
under  varying  circumstances,  the  duration  of  this  interval  may 
be  taken  as  a  measure  of  the  power  of  reflex  action.  The  shorter 
the  interval,  the  more  prone  is  the  cord  to  reflex  actions.  In 
making  observations  on  the  length  of  this  interval,  it  is  as  well 
to  use  very  dilute  acid,  such  as  will  only  just  give  a  sensation 
of  acidity  when  applied  to  the  tongue. 

Obs.  VII.  Simple  water  of  a  sufficiently  high  temperature 
(25°-  35°C.)  may  be  used  instead  of  the  acid.  It  has  the  ad- 
vantage of  being  less  likely  than  the  acid  to  produce  a  perma- 
nent action  on  the  skin.     The  difficulty,  however,  of  keeping 


410  REFLEX    ACTIONS. 

up  exactly  the  same  temperature  renders  it  unsuitable  for  com- 
parative experiments. 

In  all  the  above  experiments  the  movements  produced  bear 
marks  of  purpose.  As  the  result  of  stimulation  of  a  particular 
region  of  the  surface  of  the  body,  we  find  a  complicated  move- 
ment, a  movement  brought  about  by  the  contraction  of  certain 
muscles  and  sets  of  muscles,  acting  in  a  definite  combination 
and  sequence.  The  movement  thus  produced  is  apparently 
directed  towards  an  end.  Thus  when  the  foot  is  pinched  or 
irritated  by  the  acid,  the  resulting  movements  appear  at  least 
directed  towards,  and  frequently  actually  effect,  the  withdrawal 
of  the  foot  from  the  offending  object ;  when  the  flank  is  pinched, 
the  movement  is  such  as  tends  to  thrust  away  the  points  of  the 
forceps ;  when  the  anus  is  pinched  to  kick  away  the  forceps, 
and  so  on. 

This  purposeful  character  of  reflex  actions  may  be  still  more 
conveniently  shown  b}r  adopting  the  following  method  : — 

Obs.  VIII.  Arrange  the  frog  with  the  legs  alone  free  ac- 
cording to  the  second  method  given  above.  Cut  small  pieces 
of  blotting-paper  about  1  or  2  millimetres  square,  dip  them  in 
strong  acetic  acid,  remove  from  them  all  superfluous  acid,  and 
then  place  them  on  definite  regions  of  the  skin.  In  this  wa}'  the 
stimulus  may  be  limited  to  very  small  areas  chosen  at  pleasure  ; 
and  it  will  be  found  that  very  different  movements  of  the  hind 
limbs  will  be  produced  by  applying  the  morsel  of  paper  to  dif- 
ferent regions  of  the  body.  Thus  if  the  morsel  be  placed  on 
the  heel  of  one  foot,  both  feet  will  be  violently  rubbed  together, 
while  the  legs  remain  foreibty  extended.  If  the  morsel  be 
placed  on  one  flank,  it  will  be  rubbed  off  by  the  foot  of  the 
same  side  ;  if  it  be  placed  in  the  mid-line  of  the  back,  either  or 
both  feet  will  be  employed  to  remove  it,  and  so  on. 

The  student  will  do  well  to  map  out  the  limbs  and  bod}r  of 
the  frog  into  small  areas,  and  to  determine  the  characters  of 
the  movements,  which  result  from  the  stimulation  of  each 
area.  He  will  in  this  way  find  abundant  instances  of  an  appa- 
rent purpose. 

06s.  IX.  It  has  been  seen  that  where  the  morsel  of  acid 
paper  is  placed,  say  on  the  right  flank,  it  is  the  right  leg,  and 
the  right  leg  only,  which  under  ordinary  circumstances  is  used 
to  rub  off  the  paper.  Choosing  a  strong  frog,  in  which  reflex 
action  has  been  found  to  be  highly  developed,  suspend  it  ac- 
cording to  the  second  method,  hold  the  right  leg  firmly  down, 
or  load  it  with  a  greater  weight  than  the  leg  is  able  to  lift,  and 
apply  a  morsel  of  acid  paper  to  the  right  flank.  Twitchings 
and  convulsive  movements  of  the  right  leg  are  first  witnessed, 
and  then  the  left  leg  is  brought  up  to  rub  the  right  flank. 

Place  a  similarly  strong  frog  with  powerful  reflex  capabilities 
on  its  back  on  the  table. 


BY    DR.    MICHAEL    FOSTER.  41 1 

If  a  morsel  of  paper  were  now  placed  on  the  surface  of  the 
right  thigh,  the  right  foot  would  be  brought  up  to  rub  away 
the  paper,  the  left  foot  remaining  quiet.  Hold  tight  the  right 
foot,  or  better  still,  place  a  ligature  below  the  right  knee,  and 
cut  away  the  whole  lower  leg  and  foot.  If  the  acid  paper  be 
now  placed  on  the  right  thigh,  convulsive  twitching  of  the 
stump  (ineffectual  as  far  as  the  removal  of  the  paper  is  con- 
cerned) will  follow,  and  then  the  left  foot  will  be  brought 
across  to  rub  the  paper  away.  % 

In  both  these  cases  we  have  instances  of  an  apparent  power 
of  the  organism,  even  in  the  total  absence  of  the  brain,  to 
change  its  customary  proceeding  and  to  adapt  itself  at  once 
to  new  circumstances,  instances  which  have  led  some  to  speak 
of  a  conscious  intelligence  residing  in  the  spinal  cord. 

Obs.  X.  As  an  instance  tending  directly  to  the  contrary 
supposition,  the  following  experiment  may  be  performed: — 

In  a  shallow  glass  or  porcelain  dish,  place  enough  water  to 
reach  up  to  the  head  of  a  frog.  Line  the  sides  and  bottom 
of  the  vessel  inside  with  felt  or  blotting-paper. 

Place  an  unmutilated  frog  in  the  water,  and  then  graduall}" 
raise  the  temperature.  Cover  the  top  of  the  vessel  with  a 
piece  of  gauze  or  netting,  to  prevent  the  escape  of  the  frog. 

As  the  temperature  rises  the  frog  becomes  uneasy,  and  after 
20°  C  or  30°  C  is  reached  makes  violent  attempts  to  escape. 

Place  in  exactly  similar  circumstances  a  frog  whose  medulla 
has  been  divided  ;  the  water  should  cover  the  whole  of  the 
animal  up  to  just  below  the  wound  in  the  neck  (care  being 
taken  that  the  water  gains  no  access  to  the  spinal  cord). 

Up  to  30°  or  above,  no  movement  of  any  kind  is  visible. 
About  35°,  slight  twitch ings  may  be  observed  in  some  of  the 
muscles  of  the  limbs  and  flanks.  At  38°-40°  the  whole  body 
becomes  rigid  (rigor  caloris),  and  the  frog  is  dead  without 
having  made  the  slightest  attempt  to  escape  from  the  hot 
water. 

This  observation  goes  quite  as  far  to  prove  that  the  frog,  in 
the  absence  of  the  brain,  has  no  consciousness  or  volition  as 
Observation  IX.  seems  to  point  to  the  contrary.  Both  obser- 
vations are  probably  to  be  explained  without  any  reference, 
negative  or  positive,  to  consciousness  or  volition. 

Oba.  XI.  As  a  useful  exercise,  the  student  may  lay  bare  the 
roots  of  the  7th,  8th,  9th,  and  10th  spinal  nerves  as  directed 
in  Chap.  XXXII.,  the  medulla  having  previously  been  divided. 
Let  him  now  divide  the  posterior  root  of  say  the  tth  nerve, 
and  determine  on  what  parts  of  the  skin  the  acid  papers  may 
be  placed  without  producing  reflex  actions.  In  this  way  he 
may  ascertain  the  distribution  in  the  skin  of  the  sensory  fila- 
ments of  that  nerve  ;  and  in  the  same  way  with  the  other 
nerves. 


412  REFLEX    ACTIONS. 

068.  XIT.  Having  divided  the  medulla,  make  a  tran verse 
incision  over  the  spine  a  little  below  the  level  of  the  fore  limbs 
(fig.  2C>C),  line  c-d)  cut  through  very  carefully  a  vertebral  arch 
on  each  side  of  the  middle  line  and  remove  the  piece.  With 
a  sharp-pointed  scalpel,  the  spinal  cord  may  be  divided  right 
across. 

After  the  shock  has  passed  away,  it  will  be  found  that  reflex 
actions  xmxy  be  called  forth  in  the  fore  limbs  by  stimulating 
the  skin  of  the  fore  limbs  or  of  the  fore  part  of  the  body, 
without  any  movement  whatever  being  produced  in  the  hind 
limbs  ;  and  vice  verm.  By  the  operation,  the  body  hns  be- 
come divided  into  two  segments,  which,  as'  far  as  all  reflex 
actions  are  concerned,  are  quite  independent  one  of  the  other. 
Sometimes,  when  the  movements  of  one  segment  are  very 
violent,  the  other  segment  becomes  displaced,  the  displace- 
ment serves  as  a  stimulus,  and  a  reflex  action  is  thereby  indi- 
rectly brought  about.  But  this  will  not  be  confounded  with 
direct  reflex  actions,  which  can  only  be  called  forth  by  stimu- 
lating the  respective  segments. 

Obs.  XIII.  In  any  of  the  above  frogs  which  have  shown 
good  reflex  actions,  destroy  the  spinal  cord  entirely  by  thrust- 
ing a  wire  or  blunt  needle  down  the  spinal  canal.  All  reflex 
actions  will  at  once  and  for  ever  cease. 

Obs.  XIV.  The  orderly  and  purposeful  character  of  reflex 
actions  may  be  modified  by  the  action  of  certain  poisons,  more 
particularly  by  strychnia. 

Having  divided  the  medulla  in  a  frog,  suspend  the  animal 
as  in  Obs.  III.  and  determine  the  readiness  with  which  reflex 
action  is  produced  by  mechanical  stimulation.  This  may  be 
taken  as  a  measure  of  the  reflex  excitability  of  the  spinal  cord 
(the  acid  method  being  unsuitable  in  this  case). 

Introduce  into  the  back  of  the  frog  a  ^oVff  or  Wott  °f  a 
grain  of  strychnia  sulphate  and  determine  again  after  a  short 
interval  the  effects  of  mechanical  stimulation.  They  will  be 
found  to  be  increased,  i.  e.,  the  reflex  excitability  has  become 
heightened. 

Now  inject  a  larger  quantity  of  the  poison,  and  in  a  very 
short  time  a  very  marked  change  becomes  obvious.  The 
movement  resulting  from  the  stimulus  is  no  longer  a  simple 
movement,  for  instance,  a  simple  withdrawal  of  the  foot,  but 
a  tetanic  extension  of  the  leg,  which  becomes  more  and  more 
violent  and  prolonged. 

Soon  each  application  of  the  stimulus  will  give  rise  to  a 
prolonged  tetanic  movement  which  is  no  longer  confined  to 
the  limb,  or  even  to  the  side  stimulated.  The  hind  limbs  are 
forcibly  extended,  the  fore  limbs  bent  over  the  sternum,  and 
every  muscle  of  the  trunk  is  thrown  into  a  state  of  prolonged 
tetanic  contraction. 


BY    DR.    MICHAEL    FOSTER.  413 

After  a  while  these  contractions  pass  off  and  the  body  and 
limbs  become  once  more  relaxed.  With  each  application  of 
the  stimulus  the  same  tetanus  of  the  whole  body  is  called  forth, 
no  matter  to  what  part  of  the  body  the  stimulus  be  applied,  or 
what  be  the  character  of  the  stimulus.  The  purposeful  nor- 
mal reflex  actions  are  lost  in  a  complete  spasm  of  the  whole 
body. 

It  is  possible  to  conceive  that  this  result  might  be  brought 
out  by  an  abnormal  intensity  of  the  impulses  generated  in 
the  afferent  nerve  by  the  stimulus,  or  by  an  abnormal  irrita- 
bility of  the  total  muscular  system,  or  by  an  abnormal  condi- 
tion of  the  spinal  cord.  That  the  last  and  not  either  of  the 
former  two  is  the  real  cause,  is  shown  by  the  following  obser- 
vation. 

Obs.  XV.  In  a  frog  with  divided  medulla,  ligature  the  hind 
limbs,  leaving  the  nerves  free  as  directed  in  Chap.  XXXI.  for 
urari,  and  afterwards  inject  a  small  dose  of  strychnia. 

In  spite  of  the  absence  of  the  blood-current  in  the  lower 
limbs,  the  reflex  actions  will  be  as  manifest  in  them,  and  as 
easily  brought  about  by  stimulating  them,  as  under  ordinary 
circumstances.  But  by  the  ligature  the  strychnia  has  been 
prevented  from  having  access  to  either  the  sensory  nerves  or 
the  motor  nerves  and  muscles  of  the  hind  limb.  Hence  the 
tetanic  character  of  the  reflex  actions  produced  in  them  must 
be  due  entirely  to  the  changed  conditions  of  the  spinal  cord 
itself. 


CHAPTER  XXXIV. 

ON  SOME  FUNCTIONS  OF  CERTAIN  PARTS  OF  THE 
ENCEPHALON. 

Most  of  the  experiments  illustrating  this  part  of  the  sub- 
ject, like  those  having  to  do  with  the  conduction  of  impulses 
through  the  spinal  cord,  are  of  a  kind  which  the  student  can- 
not be  expected  to  perform  for  himself,  and  are  consequently 
not  introduced  here.  Several  observations,  however,  of  a  very 
instructive  character  may  be  made  on  the  frog. 

The  brain  of  the  frog  may  be  considered,  for  present  physio- 
logical purposes,  as  consisting  of  three  segments.  We  have 
first  the  medulla  oblongata  (fig.  296  M.  0),  and  small  cerebel- 
lum c.  next  the  optic  lobes,  L.  Op.,  easily  recognized  in  an 
operation  by  the  pigment  contained  in  their  pia  mater,  and 
lastly,  the  cerebral   hemispheres  H.  C  lying  over  the  corpora 


414  ON   SOME   FUNCTIONS   OF   THE   ENCEPHALON. 

striata,  with  the  small  optic  thalami  Th.  0  between  them  and 
the  optic  lobes. 

The  position  of  the  optic  lobes  pretty  well  corresponds  to 
the  hind  part  of  the  fron to-parietal  bones,  which  are  distinctly 
seen  when  the  skin  over  the  skull  is  removed.  A  transverse 
incision  made  through  the  skull  with  a  narrow  strong  blade. 
in  a  line  which  runs  as  a  tangent  to  the  anterior  borders  of 
the  membranse  tympani,  will  separate  the  cerebral  from  the 
optic  lobes.  This  may  be  done  without  removing  even  the 
skin.  In  most  cases,  however,  it  is  better  to  remove  the  roof 
of  the  skull  and  to  see  the  parts  of  the  brain  which  are  being 
operated  on. 

The  frog  being  placed  under  chloroform,  make  a  longitudi- 
nal incision  over  the  mid-line  of  the  skull  from  behind  the 
nose  backwards,  and  convert  it  into  a  T  incision  by  a  trans- 
verse cut  immediately  behind  the  membranse  tympani  (fig.  266, 
e.f  a  b.).  Hook  back  the  flaps.  With  a  pair  of  fine  bone 
forceps  or  strong  scissors  cut  right  across  the  fronto-parietal 
bones  where  they  overlap  the  ethmoid.  Each  bone  may  then 
be  easily  seized  by  its  front  end  and  torn  away  without  any 
injury  to  the  cerebrum  below.  That  being  done,  the  blade  of 
a  pair  of  scissors  may  be  carefully  slipped  under  eacli  parietal 
bone  close  to  its  external  border  and  the  bone  cut  through. 
The  bones  may  then  be  carefully  seized  at  their  front  border 
with  a  pair  of  forceps,  lifted  up  and  torn  away.  If  the  blood- 
vessels at  the  side  have  been  avoided,  there  will  be  but  little 
bleeding,  and  what  does  occur  will  soon  cease.  The  cerebrum 
may  now  be  simply  divided  from  the  optic  lobes  by  a  trans- 
verse incision  and  removed.  A  better  method,  in  order  to 
prevent  any  injury  to  the  optic  nerves  and  optic  thalami,  is  to 
cut  across  the  cerebral  lobes  at  their  junction  with  the  olfac- 
tory lobes,  fig.  296  L.  oh,  to  lift  up  their  cut  ends  and  so  to 
remove  them  carefully,  working  gradually  backwards.  To 
separate  the  optic  lobes  from  the  medulla,  nothing  more  than 
a  simple  transverse  incision  is  necessary,  taking  care  not  to 
injure  the  cerebellum  ;  but  it  is  as  well  to  remove  all  the  parts 
in  front  of  the  incision.  The  flaps  of  skin  may  then  be 
brought  together  and  united  by  a  couple  of  sutures,  and  the 
animal  left  to  recover  from  the  operation.  All  plugging,  etc., 
should  be  avoided. 

Obs.  I.  The  phenomena  of  a  frog  when  the  animal  possesses 
the  medulla  oblongata  and  cerebellum  as  well  as  the  spinal 
cord,  but  all  the  rest  of  brain  has  been  removed.  The  follow- 
ing facts  may  be  observed  after  the  animal  has  completely 
recovered  from  the  operation,  and  should  be  compared  with 
the  phenomena  of  a  frog  possessing  a  spinal  cord  only. 

The  attitude  is  completely  normal,  quite  different  from  that 


BY   DR.    MICHAEL   FOSTER.  415 

of  a  frog  possessing  the  spinal  cord  only.     The  head  is  well 
raised  on  the  fore  limbs. 

Respiration  goes  on  in  an  almost  normal  manner. 

If  left  to  itself,  and  protected  from  all  external  stimuli,  the 
animal  will  remain  perfect^  motionless.  For  some  little  time 
after  the  operation  has  been  performed,  movements  apparently 
voluntary,  that  is,  occurring  without  any  obvious  cause,  are 
frequently  witnessed.  These,  however,  generally  cease  after  a 
little  while,  and  if  the  animal  lives  long  enough  for  the  wound 
to  heal,  entirely  disappear. 

The  animal  will  not  feed  of  itself.  Flies,  worms,  etc.,  may 
be  placed  close  to  it,  and  even  introduced  between  the  teeth, 
without  any  notice  being  taken  of  them.  If,  however,  the 
mouth  be  opened  and  a  morsel  be  introduced  into  the  pharynx, 
it  is  swallowed.  In  this  way  the  animal  may  be  kept  alive  for 
an  indefinite  period,  being  fed  on  pieces  of  worm  or  flesh  ;  frog's 
flesh  does  very  well ;  care  must  be  taken  not  to  introduce  too 
large  pieces,  and  not  to  feed  too  often. 

If  the  skin  round  the  anus  be  pinched,  the  animal  does 
more  than  simply  kick  out  its  hind  legs  :  it  leaps  forward,  often 
repeating  the  leap  several  times,  and  springing  forward  a  con- 
siderable distance ;  sometimes  it  crawls  instead  of  leaping,  and 
not  unfrequently  does  both.  If  placed  on  its  back,  it  imme- 
diately turns  over  again  to  its  normal  position.  This  it  does 
instantly  and  with  vigor.  It  has  to  be  held  down  forcibly  in 
order  to  keep  it  on  its  back  for  any  length  of  time. 

If  thrown  into  a  basin  of  water,  it  at  once  begins  to  swim, 
and  continues  swimming  about  with  considerable  energy  till 
it  finds  some  resting-place.  Having  found  a  suitable  support, 
it  crawls  upon  it,  and  assumes  the  normal  attitude,  and  there 
remains  motionless  until  again  disturbed. 

If  the  cerebellum  be  removed,  all  these  movements  and 
habits  become  much  impaired,  much  feebler,  and  less  striking; 
or  may  (with  the  exception  of  the  respiratory  movements)  be 
wholly  absent,  but  it  is  difficult  to  remove  the  entire  cerebellum 
without  injury  to  the  medulla.  Hence  the  share  taken  bjT  each 
organ  in  keeping  up  these  powers  of  executing  complicated 
movements  cannot  be  readily  ascertained. 

The  above  facts  all  point  to  the  existence  in  this  part  of  the 
brain  of  some  mechanism  connected  with  the  co-ordination  of 
movements.  The  crawling,  leaping,  swimming,  and  turning 
over  on  to  the  belly  all  demand  a  more  complex  nervous 
machinery  than  is  needed  for  the  purely  spinal  reflex  actions, 
intricate  as  many  of  these  are. 

The  persistence  of  what  we  have  called  the  normal  attitude 
is  very  remarkable.  Strictly  speaking,  the  natural  frog  varies 
its  attitude  constantly,  but  its  most  common  posture,  the  one 
into  which  it  naturally  falls  when  at  rest,  is  the  one  we  have 


41G      ON  SOME  FUNCTIONS  OF  THE  ENOEPHALON. 

described.  This  attitude  is  the  one  to  which  the  frog  with 
cerebellum  and  medulla  clinga  most  rigidly,  to  which  it  always 
returns  after  being  disturbed,  and  in  which  it  eventually  dies 
if  left  alone  and  not  fed. 

Obs.  II.  Influence  of  the  presence  of  optic  l<>l,r.<, —  Remove 
the  parts  in  front  of  the  optic  lobes  as  directed  ;  the  best  re- 
sults are  obtained  when  the  animal  is  allowed  to  remain  per- 
fectly quiet  for  a  day,  or  for  several  hours  at  least,  after  the 
operation. 

All  the  facts  mentioned  in  Obs.  I.  may  also  be  observed  in 
this  case  ;  in  addition,  there  are  certain  phenomena  which  are 
only  witnessed  when  the  optic  lobes  are  present. 

Goltz's  Balancing  Experiment. — Place  the  frog  on  a  rough 
board  (about  eight  or  nine  inches  square),  somewhat  near  to 
one  of  the  edges.  Hold  the  board  horizontal,  and  the  frog 
will  remain  motionless  in  the  normal  attitude. 

Tilt  the  board  gradually  up,  with  that  edge  uppermost  which 
is  farthest  away  from  the  frog,  and  towards  which  he  should 
be  looking.  Up  to  an  angle  of  about  45°  and  beyond  no 
change  will  be  observed  in  the  frog.  As  soon,  however,  as 
the  board  becomes  so  much  inclined  that  the  centre  of  gravity 
of  the  frog  is  thrown  outside  the  lower  edge,  the  frog  will 
begin  to  creep  up  the  board.  As  the  inclination  proceeds,  the 
frog  moves  higher  and  higher  up,  until,  wdien  the  board  at  last 
becomes  vertical,  the  frog  will  be  found  seated  in  the  normal 
attitude,  on  the  upper  edge.  On  continuing  the  movement 
of  the  board,  so  that  what  was  the  upper  surface  becomes  the 
lower,  the  frog  will  move  from  the  edge  downward  over  the 
now  upper  surface  ;  and  when  that  surface,  by  the  continuance 
of  the  revolving  motion,  again  becomes  inclined  upward,  will 
again  creep  over  it  as  before  towards  the  new  upper  edge. 

Evidently  here  the  disturbance  of  the  centre  of  gravity  pro- 
duces such  an  effect  as  to  give  rise  to  movements  which  are 
directed  towards  the  re-establishment  of  equilibrium,  and  which 
are  continued  until  that  result  is  achieved.  At  first  sight  this 
may  appear  very  much  like  an  act  of  conscious  intelligence,  but 
if  the  student  carefully  observes  the  different  behavior  of  an 
entire  frog  and  of  a  frog  in  this  condition,  the  contrast  between 
the  two  will  be  found  very  striking.  This  frog  does  nothing 
but  crawl,  and  stops  crawling  as  soon  as  the  stimulus  of  the 
disturbed  equilibrium  passes  away.  When  the  experiment  is 
successful,  he  remains  perched  motionless  on  the  edge  of  the 
vertical  board,  and  never  leaps  away.  The  entire  frog  leaps 
away  at  once. 

Goltz's  Croaking  Experiment. — Place  the  frog  on  the  table, 
and  with  the  thumb  and  forefinger  gently  stroke  down  the 
flanks  on  either  side.  A  little  very  gentle  pressure  must  be  ex- 
ercised.    As  the  thumb  is  thus   carried  backward  along:  the 


BY    DR.    MICHAEL    FOSTER.  417 

sides  of  the  animal,  he  will  utter  a  single  distinct,  sharp,  short 
croak,  and  as  often  as  the  movement  is  repeated  the  croak  will 
be  heard. 

This  again  is  very  different  from  the  behavior  of  the  entire 
frog.  The  entire  frog,  when  thus  stroked,  may  or  may  not 
croak;  for  a  single  stroke  he  may  croak  several  times,  or  not 
at  all.  The  frog  without  the  cerebral  hemispheres,  but  posses- 
sing the  optic  lobes,  and  otherwise  in  good  condition,  croaks 
at  every  stroke,  and  croaks  once  only  for  each  stroke. 

One  seems  driven  to  regard  this  behavior  as  the  result  of  a, 
so  to  speak,  croaking  mechanism  ;  and  not  as  the  act  of  a  con- 
scious intelligence. 

Obs.  III.  The  cerebral  hemispheres  having  been  carefulby  re- 
moved, in  such  a  way  as  to  leave  intact  the  optic  nerves,  the 
student  may  attempt  the  following  experiment  of  Goltz  to  test 
the  persistence  of  any  visual  sensations. 

Place  the  frog  on  the  table,  with  his  head  towards  the 
window,  and  some  six  or  eight  inches  in  front  of  him  place  a 
large  book,  or  other  thoroughly  opaque  mass.  Gently  pinch 
him  behind,  in  any  spot  which  is  exactly  in  the  median  line  of 
his  body.  Under  ordinary  circumstances,  he  would  spring  for- 
ward in  a  straight  line,  and,  in  the  absence  of  all  vision,  would 
strike  his  head  against  the  book.  It  will  be  found  in  this  case, 
however,  if  the  experiment  be  successful,  that  instead  of  spring- 
ing forward  in  a  straight  line,  he  turns  a  little  to  the  right  or 
to  the  left,  so  as  to  avoid  the  book. 

If  he  turns  to  the  left,  shift  the  book  to  the  left  and  then 
repeat  the  experiment.  He  will  now  move  in  a  straight  line  or 
to  the  right.  In  the  same  way,  if  the  book  be  to  the  right  he 
will  incline  to  the  left. 

The  student  will  do  well  to  try  this  experiment,  but  it  fre- 
quently fails.  Care  should  be  taken  to  have  the  light  coming 
into  the  room  as  directly  in  front  of  the  animal  as  possible,  in 
order  to  exaggerate  the  shadow  cast  by  the  book.  Apparently 
the  image  of  the  opaque  book  produces  some  sort  of  visual  im- 
pression sufficient  to  guide  the  movements  of  the  animal.  But 
it  would  be  hazardous  to  say  that  the  animal  sees,  for  it  is  diffi- 
cult, or  rather  impossible,  to  obtain  any  other  evidence  of  the 
influence  of  vision  in  a  frog  in  such  a  condition. 

These  observations  arc;  introduced  to  illustrate  the  fact  that, 
in  the  absence  of  the  cerebral  hemispheres,  whether  the  optic 
lobes  be  present  or  no,  the  frog  possesses  no  volition.  He  exe- 
cutes none  of  those  so-called  spontaneous  movements  which  we 
are  in  the  babit  of  attributing  to  volition.  This  leads  us  to  infer 
the  absence  of  at  least  that  amount  of  consciousness  which  we 
find  inseparably  connected  with  volition.  At  the  same  time, 
we  learn  that  the  presence  of  certain  parts  of  the  brain  lying 
behind  the  cerebrum,  determines  the  nature  of  the  movements 
27 


418  ON   SOME   FUNCTIONS    OF   TIIE    ENCEPIIALON. 

which  arc  called  forth  by  external  stimuli,  rendering  them  very 
complicated  and  delicate,  especially  giving  them  features  which 
cause  them  closely  to  resemble  ordinary  voluntary  movements, 
and  suggesting  the  idea  of  intricate  arrangements  within  certain 
parts  of  the  brain,  of  afferent  (including  nerves  from  the  sense 
organs)  and  efferent  nerves  and  nervous  centres,  winch  maybe 
set  into  action  by  volition  on  the  one  hand,  or  by  some  external 
stimulus  on  the  other. 

Obs.  IV.  Inhibitory  Influence  of  parts  of  the  Brain  over  the 
Reflex  Actions  of  the  Spinal  Cord. 

The  reflex  actions  of  the  cord  much  more  readily  occur,  and 
are  much  more  vigorous  and  complete,  in  the  absence  than  in 
the  presence  of  the  brain.  The  brain,  therefore,  must  in  some 
way  or  other  prevent  reflex  actions. 

Irritation  of  the  optic  lobes. — Having  prepared  a  frog,  as  in 
Obs.  II.  etc.,  ascertain  the  intensity  of  the  reflex  activity  by  the 
sulphuric  acid  method.     (Chapter  XXXIII.,  Obs.'YI.). 

Touch  with  a  small  crystal  of  sodium  of  chloride,  or  with  the 
point  of  a  brush  dipped  in  saline  solution,  the  cut  surface  of 
the  optic  lobes  and  determine,  after  a  few  seconds  before  con- 
vulsions, which  may  occur,  have  set  in,  the  duration  of  the 
interval  between  the  exposure  of  the  foot  to  the  acid  and  its 
withdrawal.  It  will  be  found  to  be  greatly  prolonged.  In 
other  words,  irritation  of  the  optic  lobes  has  interfered  with,  or 
partially  inhibited,  the  reflex  action  of  the  eord.  If  the  optic 
lobes  be  removed,  and  the  medulla  irritated  instead,  the  result 
will  be  much  less  marked. 

Obs.  V.  Having  prepared  a  frog  with  optic  lobes,  and  deter- 
mined the  reflex  interval  as  above,  inject  into  the  back  \  grain 
of  quinine  sulphate,  and  determine  the  interval  again  from  time 
to  time.     It  will  be  found  to  be  much  prolonged. 

Having  prepared  a  frog  with  divided  medulla  (Chapter 
XXXIII.),  and  determined  the  duration  of  the  reflex  interval, 
inject  the  same  quantity  of  quinine,  and  again  determine  the 
interval  as  before.  No  prolongation  of  the  interval  will  be  ob- 
served. These  results  may  be  explained  bj*  supposing  that  the 
quinine  is  unable  to  act  directly  on  the  reflex  activity  of  the 
cord,  but  is  able  either  to  stimulate  an  inhibitory  mechanism 
in  the  brain,  or  at  least  to  affect  the  brain  in  such  a  manner  as 
to  interfere  with  the  reflex  actions  of  the  cord. 

Obs.  VI.  Removal  of  the  Cerebral  Hemispheres  in  the  Bird. — 
Select  a  vigorous  pigeon,  so  young  as  to  be  just  able  to  fly  well. 
Keep  it  on  dry  food  for  a  few  days,  in  order  to  avoid  an  excess 
of  bleeding. 

Having  placed  it  under  chloroform,  using  as  little  chloro- 
form as  possible,  make  an  incision  in  the  median  line  over  the 
roof  of  the  skull,  and  hook  back  the  two  flaps  of  skin.  The 
thin  skull  may  now  be  easily  cut  through  with  a  pair  of  scis- 


BY   DR.    MICHAEL   FOSTER.  419 

sovs.  and  the  roof  removed.  Without  waiting  to  stop  the 
bleeding,  draw  the  cerebral  hemispheres  gently  forward,  and 
cany  a  traverse  incision  from  side  to  side  with  a  blunt- 
pointed  bistoury  through  the  brain  in  front  of  the  corpora 
bigeminal,  and  with  a  narrow  spatula  remove  the  hemispheres 
en  masse  from  behind  forwards.  Place  the  animal  on  a  perch, 
and  leave  it  to  itself.  Do  not  attempt  to  plug  or  staunch  the 
bleeding ;  a  clot  will  soon  form  and  serve  as  the  best  protec- 
tion against  further  bleeding.  Postpone  putting  sutures  into 
the  flaps  of  skin  until  the  bleeding  has  wholly  ceased. 

If  it  be  desired  to  keep  the  animal  alive  for  any  length  of 
time,  it  will  be  as  well  to  allow  it  to  remain  perfectly  quiet  for 
some  time  after  the  operation,  avoiding  all  observations  and 
experiments  upon  it.  Only  on  the  second  or  third  day  begin 
to  feed  it  gradually  with  a  few  grains  of  softened  barley  or 
of  rice. 

Otherwise,  observations  may  be  begun  as  soon  as  the  bleed- 
ing has  ceased. 

The  bird  so  deprived  of  its  cerebral  hemispheres  (together 
with  its  corpora  striata  and  optic  thalami),  if  placed  on  the 
finger  or  on  a  perch,  will  settle  itself  in  a  balanced  position, 
and  remain  thus  for  an  indefinite  period  motionless,  or  all  but 
motionless,  except  as  far  as  the  breathing  is  concerned.  It 
seems  to  be  plunged  in  the  most  profound  sleep,  with  the  head 
drooping  and  the  ej'elids  closed. 

If  irritated,  it  appears  to  awake;  it  opens  its  eyes,  raises  its 
head,  and  more  or  less  opens  its  wings,  and  otherwise  moves 
its  bod}'  or  limbs. 

If,  while  in  a  state  of  complete  rest,  perched  on  the  fore- 
finger, the  finger  be  gently  revolved,  so  as  to  throw  the  centre 
of  gravity  outside  the  finger,  the  wings  will  immediately  spread 
out  as  if  for  the  act  of  flight. 

If  thrown  into  the  air,  it  will  actually  fly  for  some  little  dis- 
tance, eventually  settling  down  into  its  lethargic  but  balanced 
condition.  If  in  its  flight  it  meets  any  objects  it  blindly  strikes 
against  them. 

For  a  detailed  description  of  the  phenomena  exhibited  by 
such  a  bird,  see  Flourens's  Systome  Nerveux,  p.  123. 

06*.  VII.  Removal  of  the  Cerebral  Hemispheres  in  the  Mam- 
mal.— A  young  rabbit,  about  two  months  old,  is  the  most  suit- 
able animal  to  operate  upon.  It  should  be  fed  for  some  days 
previouslj-  on  dry  food.  The  method  of  operating  is  very 
much  the  same  as  in  the  bird.  Fasten  the  animal  on  a  Cer- 
mak's  rabbit-holder  (Fig.  204),  which  should  be  raised  at  an 
angle  of  60°  or  so,  in  order  that  the  head  may  be  as  high  as 
possible,  and,  consequently,  the  bleeding  diminished.  The 
removal  of  the  roof  of  the  skull  will  be  facilitated  by  first 
making  a  small  hole  in  each  parietal  with  a  trephine  about  a 


420  ON    SOME    FUNCTIONS   OF    THE   ENCEPIIAL0N. 

third  of  an  inch  in  diameter,  and  thou  slipping  the  blade  of  the 
scissors  from  one  hole  to  the  other  between  the  bone  and  the 
dura  mater,  and  cutting  the  bone  through.  The  rest  of  the 
roof  may  then  be  removed  piecemeal.  Carefully  avoid  wound- 
ing the  venous  sinuses,  and  carry  the  operation  through  as 
speedily  as  possible.  The  amount  of  ether  or  chloroform  given 
should  be  no  more  than  is  absolutely  necessary  just  to  send 
the  animal  off.  Previous  ligature  of  the  carotid  does  very 
little  good,  and  only  complicates  the  operation. 

The  animal  will  not  survive  the  operation  very  long,  but  for 
several  hours  after  the  operation  the  phenomena  of  complicated 
movements  consequent  on  stimulation,  with  total  absence  of 
volition,  may  be  witnessed  as  in  the  bird  and  in  the  frog. 

Obs.  VIII.  Division  of  the  Semi-circular  Canals. — This  is 
best  performed  on  the  bird,  ex.  gr.,  a  young  pigeon'.  The  stu- 
dent should  first  make  himself  acquainted  with  the  position  and 
relation  of  the  ganals  in  a  dead  bird.  Make  a  vertical  incision 
along  the  back  of  the  head,  hook  back  the  flaps  of  skin,  scrape 
away  the  insertion  of  the  muscles  of  the  neck,  remove  the  outer 
tablet  of  the  diploe  of  the  skull  behind  each  ear,  and  pick  away 
in  minute  pieces  with  a  small  pair  of  forceps  the  cancellous 
bone,  embedded  in  which  the  hard  bony  canals  will  then  easily 
be  found. 

Having  thus  determined  their  exact  position  in  the  dead  bird, 
the  student  will  find  no  great  difficulty  in  reaching  them  by  a 
similar  proceeding  in  the  living  bodj'.  Having  found  them,  cut 
one  o,r,  better  still,  two  on  each  side  right  through  with  a  pair 
of  small  but  strong  scissors.  The  bleeding,  which  is  generally 
excessive,  may  be  staunched  by  styptics. 

Immediately  after  the  operation,  and  for  an  indefinite  time 
afterwards,  the  bird  exhibits  the  utmost  disorder  in  its  move- 
ments. Though  able  apparently  to  move  each  and  every  mus- 
cle of  its  body,  it  has  completely  lost  the  so-called  co-ordina- 
ting power.  For  a  particular  account  of  this  condition,  see 
Flourens's  Systeme  Kerveux,  p.  454,  and  Goltz  Pfluger's  Archiv. 
Vol.  III.  p.  172. 


PHYSIOLOGY. 

PART  III -DIGESTION  AND  SECRETION. 

WITH  INTRODUCTORY  CHAPTERS  ON  THE  ALBUMINOUS 
COMPOUNDS,  AND  ON  THE  CHEMISTRY  OF  THE 
TISSUES. 

By  Dr.  LAUDER  BROTTOK 


CHAPTER  XXXY. 
ALBUMINOUS  COMPOUNDS. 

Section    1. — Properties  of  Albumin. 

1.  Albuminous  bodies  occur  in  all  the  tissues  of  the  higher 
animals,  and  form  the  chief  part  of  their  bulk.  They  derive 
their  name  from  white  of  egg,  which  may  be  taken  as  a  t3rpe  of 
the  group,  and  they  all  resemble  one  another  very  closely,  both 
in  properties  and  composition.  They  contain  52.7-54.5  per 
cent,  of  carbon,  6.9-7.3  per  cent,  hydrogen,  20.9-23.5  per  cent, 
oxygen,  15.4-16.5  per  cent,  nitrogen,  and  0.8-1.6  sulphur.  In 
the  body  they  occur  partly  in  a  solid  form  and  partly  in  solu- 
tion. The  herbivora  derive  them  from  vegetables  in  which 
they  are  contained,  and  the  carnivora  from  the  animals  on  which 
they  feed.  They  do  not  diffuse,  and  only  a  small  part  of  the 
albuminous  matter  taken  as  food  passes  through  the  walls  of 
the  alimentary  canal  into  the  circulation  unchanged.  The 
greater  portion  is  converted  into  diffusible  bodies  nearly  allied 
to  albumin,  called  peptones,  which  are  readily  absorbed. 

The  organism  not  011I3'  possesses  the  power  of  transforming 
albuminous  bodies  of  one  kind  into  those  of  another,  so  that, 
e.  fj.,  the  casein  of  milk  is  converted  into  the  muscles  of  the 
sucking  infant,  but  of  combining  them  with  other  substances, 
BO  as  to  form  such  compounds  as  the  haemoglobin  of  blood,  and 
of  altering  them  in  such  a  way  as  to  obtain  from  them  the  so- 


4-2:2  ALBUMINOUS    COMPOUNDS. 

called  albuminoids  of  which  connective  and  elastic  tissue,  carti- 
lage, and  epithelium  are  composed. 

Alter  serving  their  purpose  in  the  organism,  the}'  are  ex- 
creted, not,  however,  in  the  form  of  albumin,  but  in  that  of 
urea.  It  is  extremely  improbable  that  they  are  converted  di- 
rectly into  urea,  but  rather  into  leucine  and  tyrosine,  uric  acid, 
kreatin  and  [creatinine,  and  other  substances,  from  which  urea 
is  produced  by  further  decomposition.  Lately,  some  have 
seemed  inclined  to  put  forth  the  opinion  that  peptones,  after 
their  absorption,  instead  of  being  raised  again  to  the  rank  of 
albuminous  bodies,  undergo  still  further  decomposition,  and 
yield  hydro-carbons,  which  serve  as  fuel  to  the  body,  and  nitro- 
genous substances,  which  are  rapidly  converted  into  urea  and 
excreted,  while  the  waste  of  the  tissues  proper  is  supplied  by 
albumin  absorbed  as  such  from  the  alimentary  canal  (Fick). 

*  *  2.  Preparation  of  a  Solution  of  Albumin  to  be 
used  in  testing. — Egg  Albumin. — In  order  to  get  a  solu- 
tion of  albumin  for  examination,  pour  the  whites  of  two  or  three 
hen's  eggs  into  a  beaker,  and  cut  them  up  with  a  pair  of  scis- 
sors, so  as  to  liberate  the  albumin  from  the  network  of  line  mem- 
branes in  which  it  is  inclosed  ;  stir  the  viscous  fluid  vigorously 
with  a  glass  rod,  and  then  press  it  through  a  piece  of  linen. 
Mix  it  with  an  equal  quantity  of  water,  allow  it  to  stand  at 
rest  for  some  time,  and  then  filter  it.  It  passes  very  slowly 
through  the  filter  and  chokes  it  very  quickly.  Several  small 
filters  should  therefore  be  used  in  preference  to  one  or  two 
large  ones,  and  they  should  be  changed  as  soon  as  they  get 
choked.  The  filtration  should  also  be  quickened  by  the  use  of 
the  air-pump  (see  Appendix,  §  211). 

This  filtrate  contains  inorganic  salts  as  well  as  albumin,  but 
it  will  serve  perfectly  well  to  show  most  of  the  properties  of 
albumin.  For  some  purposes,  however,  serum  albumin  is  to  be 
preferred  (.see  §  18). 

*  3.  Preparation  of  Pure  Albumin. — If  pure  albumin 
is  wanted,  it  may  be  prepared  by  separating  the  inorganic  salts 
from  it  by  dialysis,  and  this  operation  is  also  useful  in  showing 
that  albumin  does  not  diffuse. 

Before  subjecting  the  diluted  and  filtered  albumin  to  dialysis, 
it  is  advisable  to  concentrate  it  by  evaporation  at  40°  C,  so  as 
to  quicken  the  diffusion  of  the  salts.  Then  place  the  concen- 
trated liquid  in  a  dialyser  (App.  §  212),  and  let  it  remain  over 
distilled  water.  Change  the  water  every  six  hours,  till  the  water 
no  longer  gives  a  turbidity  with  silver  nitrate.  As  sodium 
chloride  is  the  chief  salt  contained  in  the  egg  albumin  its  ab- 
sence in  the  ditfusate  may  be  regarded  as  a  sign  that  the  albu- 
min is  free  from  all  salts  which  diffuse.  The  vessels  used  must 
be  perfectly  clean,  and  the  distilled  water  tested  beforehand,  as 
this  test  is  very  delicate.     The  albumin  still  retains  a  certain 


BY    DR.    LAUDER    BRUNTON.  423 

proportion  of  inorganic  salts,  but  there  is  no  way  known  of 
removing  them  without  completely  altering  its  constitution. 

4.  Preservation  of  Albumin. — If  kept  in  solution, 
albumin  will  quickly  decompose,  and  it  is  inconvenient  to 
prepare  it  from  eggs  every  time  that  a  solution  is  required. 
It  may.  however,  be  preserved  for  a  long  while  by  evaporating 
the  solution  to  dryness  at  40 c  C.  (see  App.  §  208).  The  dry 
albumin  forms  a  j-ellowish  transparent  glassy  substance,  which 
may  be  kept  in  a  stoppered  bottle,  and  dissolved  as  required. 

5.  Serum  Albumin. — Preparation:  Add  very  dilute 
acetic  acid,  drop  by  drop,  to  serum  of  blood  or  hydrocele  fluid, 
stirring  it  constantly  all  the  time,  till  a  flocculent  precipitate 
is  produced.  Filter.  Add  a  dilute  solution  of  sodium  carbo- 
nate to  the  filtrate  till  it  is  nearly  neutralized  ;  evaporate  it  to 
a  small  bulk  at  40°  C. ;  separate  the  salts  by  diffusion,  and 
evaporate  the  solution  at  40°  C.  to  dryness,  in  the  same  way 
as  directed  for  egg  albumin.  It  still  contains  small  quantities 
of  salts,  but  it  is  almost  impossible  to  separate  them  from  it. 

6.  Differences  between  Serum  Albumin  and  Egg 
Albumin. — Serum  albumin  agrees  with  egg  albumin  in  most 
of  its  characters,  but  it  differs  from  it  in  the  following  re- 
spects:— 

1.  Its  solutions  are  not  coagulated  by  ether. 

2.  It  is  more  easi^  precipitated  from  its  solution  by  hydro- 
chloric acid. 

3.  It  dissolves  more  readily  in  concentrated  nitric  or  hydro- 
chloric acid,  and  the  precipitate  thrown  down  by  dilution  from 
the  solutions  in  these  acids,  as  well  as  that  thrown  down  by 
these  acids  from  solutions  in  other  menstrua,  is  readiby  and 
completely  soluble  in  the  concentrated  acids,  while  the  pre- 
cipitate of  egg  albumin  is  not. 

When  injected  under  the  skin  of  an  animal  it  does  not 
appear  in  the  urine,  while  egg  albumin  does  so  either  when 
injected  under  the  skin  or  introduced  in  large  quantities  into 
the  stomach  or  rectum  (Stockvis). 

*  7.  Solubility  of  Dry  Albumin.— In  testing  the  solu- 
bility of  albumin  or  other  substances  to  be  afterwards  men- 
tioned, they  ought  first  to  be  pulverized  and  then  agitated  or 
stirred  with  the  liquid.  If  the  powder  runs  into  masses,  these 
ought  to  be  broken  up  with  a  glass  stirring  rod  ;  this  ma}'  be 
done  much  more  easily  if  the  rod  is  very  thick  or  has  a  bulb- 
ous end. 

If  simple  agitation  or  heat  suffices  to  dissolve  a  substance, 
it  may  be  placed  in  a  test-tube,  but  if  it  requires  stirring  it 
should  be  put  in  a  test-glass  (as  the  rod  is  apt  to  break  the 
tube),  and  afterwards  transferred  to  a  tube  if  heat  is  to  be 
applied. 

The  fact  of  a  substance  being  soluble  in  a  liquid  is  ascer- 


424  ALBUMINOUS    COMPOUNDS. 

tained  by  the  quantity  which  was  at  first  put  in  becoming 
gradually  less,  and  finally  disappearing.  When  it  is  only 
sparingly  soluble  no  diminution  in  the  substance  may  be 
observable,  and  the  liquid  is  then  to  be  decanted  or  filtered  off, 
and  something  added  or  done  to  it  which  will  indicate  the 
presence  of  the  substance,  if  any  has  become  dissolved.  It  is 
sometimes  more  convenient,  especially  when  alcohol  and  ether 
are  employed  as  solvents,  to  evaporate  the  filtered  liquid  to 
dryness,  and  see  whether  it  leaves  any  residue  or  not. 

Pulverize  a  little  albumin  in  a  Wedgwood  mortar.  Put  a 
little  of  it  in  several  test-tubes,  and  test  its  solubility  in  the 
following  reagents: — 

fl.  Water:  The  albumin  will  dissolve,  and  may  be  shown 
to  be  present  in  solution  by  boiling,  when  it  will  be  precipi- 
tated. 

f  2.  Liquor  Potassse :  The  albumin  will  dissolve,  and  may 
be  precipitated  from  the  solution  by  neutralizing. 

3.  Alcohol. 

4.  Ether  :  The  albumin  does  not  dissolve  either  in  alcohol 
or  ether.  The  clear  liquid,  when  filtered  and  evaporated,  will 
leave  no  residue. 

f  5.  Acetic  Acid  dissolves  albumin.  On  adding  potassium 
ferrocyanide  to  the  solution,  a  precipitate  falls. 

fO.  Concentrated  Hydrochloric  Acid:  The  albumin  dis- 
solves, and  the  solution  gradually  becomes  blue,  then  violet, 
and,  lastly,  brown.  Test  this  with  one  portion  at  the  tempera- 
ture of  the  room,  and  with  another  heated  over  a  spirit-lamp. 
The  same  changes  will  occur  in  both,  but  much  more  quickly 
in  that  which  is  heated.  A  precipitate  falls  when  either  solu- 
tion is  neutralized. 

7.  Concentrated  Sulphuric  Acid :  The  albumin  dissolves, 
and  more  quickly  if  heated. 

8.  Concentrated  Nitric  Acid  :  The  albumin  dissolves,  form- 
ing a  yellowish  solution.  When  boiled  it  dissolves  more 
quickly.  When  the  solution  is  allowed  to  cool,  and  ammonia 
added  to  it,  it  becomes  orange  colored. 

**  8.  Coagulation  of  Albumin. — One  of  the  most  re- 
markable properties  of  albumin  is  its  precipitation  from  neutral 
solutions  as  an  insoluble  coagulum  by  boiling. 

In  heating  albuminous  solutions  care  must  be  taken  not  to 
hold  them  too  near  the  flame,  and  also  to  shake  or  stir  them 
about,  as  otherwise  the  coagulum  sticks  to  the  tube  and  be- 
comes burnt,  and  the  test-tube  cracks.  Boil  a  watery  solution 
of  albumin  in  a  test-tube;  a  coagulum  separates. 

Alkali  ajypears  to  be  set  free  during  Coagulation. — Add  a  few 
drops  of  neutral  solution  of  litmus  to  a  solution  of  albumin  and 
boil.     The  color  will  become  more  decidedly  blue. 


BY    DR.    LAUDER    BRUNTON.  425 

Circumstances  ivhich  influence  Coagulation.  Temperature 
at  ivhich  Coagulation  occurs. — Although  solutions  of  albumin 
are  generally  boiled  in  order  to  produce  coagulation,  it  takes 
place  much  below  the  boiling  point.  The  temperature  at  which 
it  occurs  sometimes  serves  to  separate  albuminous  bodies  which 
could  not  otherwise  he  distinguished  (see  §  60).  The  method 
of  ascertaining  it  is  as  follows :  Put  some  aqueous  solution  of 
albumin  in  a  test-tube;  place  it  along  with  a  thermometer  in  a 
beaker  containing  water,  and  apply  heat  very  gradually  till 
coagulation  begins  to  take  place  and  the  solution  grows  milky 
from  the  formation  of  a  precipitate.  Then  note  the  tempera- 
ture of  the  water.  If  the  liquid  is  heated  over  a  naked  flame, 
it  cannot  be  so  equally  and  gradually  warmed  throughout,  nor 
the  temperature  at  which  coagulation  occurs  so  accurately 
ascertained. 

Effect  of  Acids  and  Alkalis  on  the  Temperature  of  Coagula- 
tion.— The  addition  of  very  dilute  acetic  or  phosphoric  acid 
causes  coagulation  to  take  place  at  a  lower  temperature.  The 
addition  of  a  very  little  sodium  carbonate  pi'events  coagulation 
from  taking  place  till  the  solution  has  been  raised  to  a  higher 
temperature  than  is  necessary  in  neutral  solutions.  A  large 
quantity  will  prevent  it  altogether. 

Put  some  albumin  solution  into  three  test-tubes,  acidulate 
one  slightly  with  very  dilute  acetic  or  phosphoric  acid,  add  to 
another  a  drop  or  two  of  a  solution  of  sodium  carbonate,  and 
keep  the  third  without  any  addition,  for  the  purpose  of  com- 
parison. Put  a  drop  or  two  of  litmus  solution  into  each,  so 
that  they  may  be  distinguished  by  their  color,  or  attach  a  small 
label  to  each.  Place  all  three  in  a  beaker,  and  warm  them  as 
in  the  previous  experiment.  As  the  temperature  rises  coagu- 
lation Avill  occur,  first  in  the  acid,  next  in  the  neutral,  and  lastly 
in  the  alkaline  solution. 

Effect  of  neutral  Alkaline  Salts  on  the  Temperature  of  Co- 
agulation.— The  addition  of  neutral  alkaline  salts,  such  as 
sodium  chloride  or  sulphate,  to  a  solution  of  albumin  causes  it 
to  coagulate  at  a  lower  temperature  than  it  would  otherwise 
do.  The  salts  produce  this  effect  in  neutral,  in  acid,  and  in 
alkaline  solutions  of  albumin. 

Repeat  the  previous  experiment,  dividing  each  solution  into 
two  parts  and  adding  to  one  of  them  some  saturated  solution 
of  sodium  sulphate.  In  each  case  coagulation  will  take  place 
at  a  lower  temperature  in  the  solution  to  which  the  salt  has 
been  added  than  in  the  corresponding  one  to  which  no  addition 
has  been  made. 

As  the  acetic  acid  alone  lowers  the  temperature  of  coagula- 
tion, and  the  addition  of  neutral  salts  does  so  still  further,  the 
solution  to  which  both  have  been  added  will  coagulate  first. 
J5y  adding  a  large  quantity  of  the  salt  and  of  acetic  acid  coagu- 


426  ALBUMINOUS   COMPOUNDS. 

lation  may  be  produced  at  a  temperature  between  20°  C.  and 
30°  C.  (Hoppe-Seyler). 

f  Coagulation  is  not  due  to  heat  alone,  but  to  the  presence  of 
Water. — Take  some  perfectly  dry  albumin,  put  it  in  a  test-tube, 
cover  the  mouth  of  the  tube  and  plunge  its  lower  end  into 
boiling  water.  Keep  it  there  sufficiently  long  to  be  certain  that 
the  albumin  has  been  heated  to  100°  C.  Take  it  out,  let  it 
cool,  and  then  add  water  to  the  albumin.  It  will  be  found  solu- 
ble. Plunge  the  tube  a  second  time  into  the  boiling  water,  and 
the  solution  will  be  coagulated. 

**  9.  Precipitation  of  Albuminous  Bodies. — Though 
the  action  of  the  following  reagents  may  be  conveniently  tried 
with  a  solution  of  egg  albumin,  their  power  of  precipitating 
albumin  is  not  limited  to  that  obtained  from  eggs,  but  extends 
equally  to  all  other  albuminous  bodies. 

Take  a  solution  of  albumin  in  water,  put  some  of  it  into  ten 
test-tubes  and  add  the  following  reagents.  They  all  precipitate 
albumin. 

fl.  Concentrated  nitric  acid. 

2.  Concentrated  lrydrochloric  acid. 

3.  Concentrated  sulphuric  acid. 

f4.  Acetic  acid,  or  a  little  hydrochloric  acid,  and  afterwards 
a  solution  of  potassium  ferrocyanide. 

5.  Acetic  acid  and  a  considerable  quantity  of  a  concentrated 
solution  of  sodium  sulphate.  [Other  neutral  salts  of  the  alkalis 
or  alkaline  earths  as  well  as  gum  arabic  or  dextrin  have  a  simi- 
lar action  to  sodium  sulphate.] 

6.  Basic  lead  acetate. 

7.  Mercuric  chloride. 

8.  Tannic  acid. 

9.  Powdered  potassium  carbonate  thrown  into  the  solution 
till  it  is  almost  saturated. 

10.  Alcohol. 

**  10.  Detection  of  Albumin. — The  three  tests  ordina- 
rily used  to  detect  the  presence  of  albumin  in  a  fluid  are 

1st.  Its  precipitation  when  boiled  and  acidulated  with  nitric 
acid. 

2d.  Its  precipitation  by  acetic  acid  and  ferrocyanide  of 
potassium. 

3d.  Its  precipitation  when  boiled  with  acetic  acid  and  a  strong 
solution  of  neutral  salt. 

The  student  should  first  try  these  tests  with  a  solution 
known  to  contain  albumin,  so  as  to  become  familiar  with  tlu2tn, 
and  afterwards  with  a  solution  which  may  or  may  not  contain 
it. 

1.  Put  some  of  the  fluid  in  a  test-tube  and  heat  it  over  a 
spirit-lamp  or  Bunsen's  burner  till  it  boils.  Add  a  drop  or 
two  of  nitric  acid  so  as  to  give  it  a  most  distinctly  acid  reac- 


BY    DR.    LAUDER    BRUNTON.  427 

tion.  If  a  precipitate  is  formed  by  boiling  and  is  unchanged 
by  the  nitric  acid,  or  if  one  forms  after  the  addition  of  the 
acid,  the  fluid  contains  albumin. 

The  acid  is  added  for  two  reasons,  (a)  To  dissolve  any 
substance  which  might  be  present  in  the  solution,  and  being 
precipitated  by  boiling  might  simulate  albuminous  coagula- 
tion. Such  substances  are  calcium  phosphate  which  is  present 
in  human  urine,  and  calcium  carbonate  in  the  urine  of  herbi- 
vora.  As  this  test  is  very  frequently  used  for  detecting  albu- 
min in  urine,  these  substances  might  very  easily  lead  to  error. 
Albumin  which  has  been  coagulated  b}r  heat  is  not  soluble  in 
nitric  acid,  and  if  the  precipitate  produced  in  the  fluid  by 
boiling  disappears  on  the  addition  of  acid,  no  albumin  is 
present. 

(b)  To  neutralize  alkali  which  might  hinder  the  albumin 
from  being  precipitated  by  boiling. 

Take  some  solution  of  albumin  in  water,  add  a  few  drops  of 
liquor  potassoe  and  boil.  No  precipitate  occurs.  Add  one 
drop  of  dilute  nitric  acid — any  precipitate  which  forms  disap- 
pears on  shaking  the  tube.  Add  sufficient  to  make  the  fluid 
very  distinctly  acid,  and  a  permanent  coagulum  will  he  pro- 
duced. The  quantity  of  acid  added  must  therefore  not  be  too 
small,  or  some  albumin  may  remain  in  the  solution.  Some- 
times, instead  of  using  nitric  acid,  the  fluid  is  kept  boiling, 
and  acetic  acid  added  very  gradually  till  the  fluid  is  neutral. 
Unless  very  great  care  is  taken  to  neutralize  the  fluid  exactly, 
this  method  may  fail,  for  if  an  excess  of  acetic  acid  be  added 
it  will  retain  the  albumin  solution.  If  neutralized  exactly, 
the  albumin  will  be  precipitated,  and  may  be  separated  from 
the  fluid  by  filtration. 

2.  Acidulate  the  fluid  strongly  with  acetic  acid,  and  then 
add  several  drops  of  a  solution  of  potassium  ferrocyanide.  If 
albumin  be  present,  a  white  flocculent  precipitate  will  occur. 

3.  Add  acetic  acid  to  the  fluid  till  it  is  very  distinctly  acid, 
mix  it  with  its  own  volume  of  a  strong  solution  of  sodium  sul- 
jmate,  and  heat  to  boiling.  If  albuminous  bodies  are  present, 
a  permanent  precipitate  will  be  formed. 

This  last  method  enables  us  not  only  to  discover  albumin 
when  present,  but  to  separate  it  from  the  solution,  so  that 
tests  for  other  substances,  such  as  sugar,  with  which  the  pres- 
ence of  albumin  would  have  interfered,  may  then  be  applied 
to  it. 

11.  Separation  of  Albuminous  Bodies  from  other 
Substances  in  solution. — 1.  The  usual  way  of  separating 
albuminous  bodies  from  solutions  is  by  boiling,  so  as  to  coagu- 
late the  albumin.  If  the  solutions  are  already  acid,  they  are 
boiled   without  adding  anything,   but    if  not,  a   little  dilute 


428  ALBUMINOUS    COMPOUNDS. 

acetic  acid  is  to  be  added  before  boiling,  excess  being  carefully 
avoided. 

2.  If  complete  coagulation  is  not  produced  by  boiling  with 
acetic  acid  alone,  an  equal  volume  of  concentrated  solution  of 
sodium  sulphate  may  be  added,  and  the  liquid  again  boiled. 

**  12.  Tests  for  traces  of  Albumin  in  solution. — 1. 
Caustic  Potash  and  Copper  Test. — It  is  advisable,  before  try- 
ing this  test,  which  is  also  used  for  the  detection  of  sugar,  to 
become  acquainted  with  the  reaction  presented  when  a  caustic 
alkali  is  added  to  a  solution  of  cupric  sulphate,  and  the  mix- 
ture heated  without  any  foreign  substance  being  present  in 
the  solution.  Put  a  little  distilled  water  into  a  test-tube,  with 
a  drop  or  two  of  a  dilute  solution  of  cupric  sulphate.  Pour 
into  it  some  liquor  potassa?,  and  a  light  blue  precipitate  of 
hydrated  cupric  oxide  will  be  thrown  down.  Boil  the  liquid, 
and  the  blue  precipitate  will  be  converted  into  a  black  powder, 
which  is  anhydrous  cupric  oxide.  If  it  is  gently  warmed,  in- 
stead of  boiled,  the  powder  will  be  dark  brown. 

The  hydrated  cupric  oxide  is  not  soluble  in  excess  of  ordi- 
nary liquor  potassa?,  but  is  slightly  soluble  in  very  concen- 
trated solutions  of  potash,  and  imparts  to  them  a  light  blue 
color.  The  presence  of  certain  organic  substances  renders 
hydrated  cupric  sulphate  soluble  in  weaker  alkaline  solutions. 
Put  some  water  and  cupric  sulphate  solution  in  a  test-tube ; 
add  a  small  crystal  of  tartaric  acid,  or  a  few  drops  of  its  solu- 
tion, and  then  liquor  potassa?.  Either  no  precipitate  will  form, 
or  it  will  redissolve,  and,  on  shaking  the  tube,  the  liquid  will 
become  of  a  bright  blue  color.  Boil  it:  no  precipitate  will  fall, 
and  no  change  in  the  color  will  take  place. 

Application  of  this  Test  to  Albumin. — Put  some  solution  of 
albumin  in  a  test-tube ;  add  a  drop  or  two  of  cupric  sulphate 
and  liquor  potassa? ;  an  excess  of  liquor  potassa?  does  not  inter- 
fere with  the  reaction.  Either  no  precipitate  will  fall,  or  it 
will  be  dissolved  on  shaking  the  tube,  the  liquid  assuming  a 
violet  color.  Boil  it.  No  precipitate  falls,  but  the  violet 
color  will  become  deeper. 

**  2.  Xanthoprolein  Reaction. — Add  to  the  fluid  some  con- 
centrated nitric  acid,  and  boil.  Let  the  liquid  cool,  and  then 
add  a  little  ammonia.  If  albumin  is  present,  an  orange  color 
will  be  produced.  This  is  one  of  the  most  delicate  tests  for 
albuminous  substances. 

**  3.  Millon's  Reaction.— KM  to  the  fluid  a  little  of  Mil- 
Ion's  reagent  and  heat.  If  albumin  be  present  in  considerable 
quantities,  a  white  precipitate  will  fall  and  become  red  on  heat- 
ing ;  if  only  a  trace  be  present,  the  fluid  will  become  red.  The 
red  color  is  produced  even  at  ordinary  temperatures,  but  it  is 
increased  by  heating. 

To  prepare  Millon's  reagent  take  two  beakers,  one  of  which 


BY    DR.    LAUDER    BRUNTON.  429 

may  be  considerably  larger  than  the,  other ;  place  one  on  each 
pan  of  a  pair  of  scales,  and  add  shot  or  weights  to  the  pan 
containing  the  lighter  beaker  till  the  other  is  counterbalanced. 
Four  into  the  smaller  beaker  a  little  mercury,  and  into  the 
other  the  same  weight  of  nitric  acid  (sp.  gr.  1042).  Dissolve 
the  mercury  in  the  nitric  acid  at  first  without,  and  afterwards 
with  gentle  warmth.  Pour  the  solution  into  a  graduated  glass 
measure,  and  add  to  it  twice  its  volume  of  water.  Let  it  stand 
for  some  hours,  and  then  decant  the  fluid  from  the  crystalline 
deposit. 

Section  II. — Alteration  of  Albumin  by  Alkalis. 
Ew  albumin  is  converted  into  alkali-albuminate  when  it  is 

CO 

dissolved  in  caustic  potash  or  soda,  or  when  they  are  added  to 
its  solutions.  Alkali-albuminate  is  the  substance  first  described 
b}'  Mulder  under  the  name  of  protein.  He  considered  it  to  be 
the  essential  part  of  all  albuminous  bodies,  and  regarded  them 
as  compounds  of  it. 

Albuminous  bodies  are  not  converted  immediately  into 
alkali  albuminate,  but  they  undergo  this  change  when  allowed 
to  stand  with  caustic  alkalis,  and  it  is  greatly  accelerated  by 
the  application  of  heat. 

Alkali  albuminate  is  not  coagulated  by  heat.  It  is  soluble 
in  weak  alkalis.  It  is  precipitated  when  the  alkaline  solutions 
are  neutralized  by  acids.  It  is  soluble  in  very  dilute  acids, 
especially  hydrochloric  acid,  and  when  the  acid  is  added  in 
excess  to  an  alkaline  solution,  the  precipitate  which  was 
thrown  down  by  its  neutralization  is  again  dissolved  very 
readily  by  the  acid.  When  the  acid  solution  is  neutralized 
by  an  alkali  the  albumin  is  again  precipitated. 

If  the  alkali  albuminate  is  precipitated  by  neutralization, 
and  the  precipitate  immediately  dissolved  in  acid,  it  is  quickly 
converted  into  syntonian.  If  it  is  precipitated,  and  allowed 
to  stand  for  some  time,  it  will  still  be  dissolved  by  dilute 
acids,  but  not  so  readily  as  immediately  after  precipitation, 
and  it  must  be  warmed  with  them  to  60°  C.  in  order  to  convert 
it  into  syntonian. 

If  alkaline  phosphates  are  present  in  the  solution,  alkali 
albuminate  is  not  precipitated  by  neutralization.  When  just 
sufficient  acid  has  been  added  to  a  solution  of  alkali  albumi- 
nate to  convert  the  basic  phosphate  into  acid  phosphate,  the 
slightest  excess  of  acid,  or  even  C02  will  produce  a  precipitate. 
In  studying  the  action  of  alkalis  on  albumin,  it  is  as  well  to 
begin  with  their  action  on  solution  of  albumin,  and  afterwards 
to  examine  the  solid  alkali  albuminate. 

**  13.  Alkali  Albuminate. — Dissolve  some  albumin  in 
water  in  a  beaker  ;  add  to  it  a  few  drops  of  liquor  potassaj,  and 


430  ALBUMINOUS   COMPOUNDS. 

put  a  little  of  the  mixture  into  four  test-tubes.  The,  Alkali 
Albuminate  is  not  formed  immediately. — To  the  solution  in 
the  first  tube  add  a  drop  of  watery  solution  of  litmus  (see 
App.  §  217).  Then  add  very  dilute  acid  till  the  blue  color  of 
the  litmus  begins  to  change  to  red.  No  precipitate,  or  only  a 
very  slight  one,  will  take  place.  Boil  the  neutral  liquid  ;  a 
precipitate  is  produced  showing  that  much  unchanged  albumin 
is  still  present.  If  a  precipitate  falls,  the  presence  of  much 
unchanged  albumin  may  still  be  demonstrated  by  filtering  and 
boiling  the  filtrate,  or  adding  tannin  to  it,  when  a  precipitate 
will  be  produced.  It  is  quickly  formed  when  heat  is  applied. 
It  is  not  coagulated  by  boiling.  Gently  warm  the  fluid  in  the 
second  test-tube  till  it  boils  ;  no  precipitate  forms.  Let  it 
cool,  add  a  drop  of  litmus  to  it,  and  neutralize.  Just  when 
the  blue  begins  to  change  to  red  the  fluid  will  become  turbid 
from  the  precipitation  of  the  alkali  albuminate.  Let  the  pre- 
cipitate settle,  and  filter  the  fluid.  Boil  the  filtrate ;  no  pre- 
cipitate is  formed,  showing  that  the  whole  of  the  albumin  has 
become  insoluble  in  water,  and  has  been  precipitated  b}'  neu- 
tralization. It  is  soluble  in  dilute  acids.  Warm  and  neutral- 
ize the  solution  in  the  third  tube  as  in  last  experiment,  then 
add  an  excess  of  hydrochloric  acid  to  the  neutralized  solution, 
and  the  liquid  will  again  become  clear.  On  neutralizing  the 
solution  a  second  time  the  precipitate  re-appears.  It  is  formed 
at  ordinary  temperatures,  but  more  slowly.  Let  the  solution 
in  the  fourth  tube  stand  for  some  time,  and  then  neutralize  it. 
The  precipitate  will  be  greater  than  in  that  which  was  neutral- 
ized immediately  after  adding  the  potash.  Filter  and  test  the 
amount  of  albumin  in  the  filtrate  by  adding  tannin.  It  will 
vary,  being  greater  or  less,  according  to  the  shorter  or  longer 
time  the  solution  has  been  allowed  to  stand. 

*  14.  Preparation  of  Solid  Alkali  Albuminate. — a. 
From  esrafs.  Put  the  white  of  one  or  two  esus  in  a  beaker,  cut 
it  up  with  scissors  and  shake  it  vigorously  with  air  in  a  flask 
until  the  membranes  separate  and  come  to  the  top  with  the 
foam.  Filter  it  through  a  piece  of  linen.  Add  strong  solu- 
tion of  caustic  potash  to  it  drop  by  drop,  until  the  whole  mass 
becomes  transformed  into  a  stiff'  jelly.  Cut  it  into  pieces 
about  the  size  of  a  horse-bean  and  throw  them  into  a  large 
quantity  of  distilled  water.  Stir  them  round  and  round  a  few 
times  and  then  pour  off  the  water,  keeping  back  the  pieces  bjr 
a  piece  of  gauze  stretched  across  the  mouth  of  the  beaker. 
Wash  the  albuminate  with  fresh  water  several  times  in  order 
to  remove  the  free  alkali  until  the  pieces  begin  to  turn  white 
at  the  edges  and  exhibit  only  a  faint  though  distinct  alkaline 
reaction.  As  the  albuminate  is  soluble  in  water  containing 
alkali,  a  good  deal  of  it  is  lost  in  the  process.    When  deprived 


BY   DR.    LAUDER    BRUNTON.  431 

of  its  alkali  by  prolonged  washing  or  by  soaking  in  dilute 
acids  it  forms  2)seild°fibrin.  Like  fibrin  this  substance  is 
elastic,  and  it  swells  but  does  not  dissolve  in  dilute  hydro- 
chloric acid.  Unlike  fibrin  it  contains  no  ash,  and  when  put 
into  ln'drogen  peroxide  does  not  readily  decompose  it ;  so  that 
few  hubbies  of  gas  appear. 

b.  From  milk.  Alkali  albuminate  may  be  prepared  from 
milk  by  shaking  with  caustic  potash  and  ether,  removing  the 
ether,  precipitating  the  albuminate  by  acetic  acid  and  washing 
the  coagulum  with  water,  alcohol,  and  ether. 

15.  Properties. — Boil  some  pieces  of  albuminate  in  water; 
it  still  contains  alkali,  and  is  soluble  in  boiling  water,  forming 
a  feebly  alkaline  solution.  Let  it  cool,  divide  it  into  several 
portions  and  apply  the  following  tests  : — 

1.  Pass  CO.,  through  the  solution  and  a  precipitate  will  fall. 
No  precipitate  is  produced  if  the  solution  is  strongly  alkaline. 

2.  Add  alcohol  to  the  solution  ;  no  precipitate  is  produced. 

3.  Add  magnesium  sulphate  in  substance  till  the  solution  is 
saturated.  The  albuminate  will  be  precipitated.  Calcium 
chloride  will  have  the  same  effect. 

It  is  precipitated  by  metallic  salts  like  other  albuminous 
solutions.  It  is  precipitated  by  neutralization,  and  behaves 
to  alkaline  phosphates  like  the  solution  of  alkali  albuminate 
prepared  by  heating  solutions  of  albumin  with  potash. 

*  It  is  not  precipitated  by  Neutralization  in  presence  of 
Alkaline  Phosphates. — A  very  small  quantity  of  acid  is  suffi- 
cient to  give  a  distinctly  acid  reaction  to  a  pure  solution  of 
alkali  albuminate,  but  if  sodium  or  potassium  phosphate  is 
present  a  considerable  amount  of  dilute  acid  may  be  added  to 
the  liquid  after  the  point  of  neutralization  has  been  reached 
without  given  it  a  very  distinctly  acid  reaction  ;  for  the  acetic 
acid  and  neutral  phosphate  react  on  each  other,  forming- 
sodium  or  potassium  acetate  and  acid  phosphate.  Whenever 
the  solution  becomes  distinctly  acid,  the  albumin  is  precipi- 
tated, whether  sodium  phosphate  be  present  or  not.  If  suffi- 
cient acid  has  been  added  to  convert  all  but  a  trace  of  the 
sodium  phosphate  present  into  acid  phosphate,  the  further 
addition  of  C02will  cause  a  precipitate.  Heating  the  solution 
will  also  cause  a  precipitate,  for  it  converts  the  acid  phosphate 
into  neutral  phosphate,  and  by  thus  liberating  free  acid  acts 
just  as  the  addition  of  more  acid  would  do. 

Put  some  solution  of  alkali  albuminate  into  two  test-tubes  ; 
add  solution  of  sodium  phosphate  to  one  of  them,  and  color 
them  both  equally  witli  solution  of  litmus. 

Neutralize  them  both  with  very  dilute  acetic  acid.  Very 
little  acid  will  neutralize  the  pure  solution  of  albuminate,  and 
the   slightest   excess    will   at   once   turn   the   litmus   red.     A 


432  ALBUMINOUS   COMPOUNDS. 

greater  quantity  may  lie  added  to  the  other  without  turning  it 
red.  and  till  it  turns  red  no  precipitate  will  fall.1 

16.  Alkali  Albuminate  should  contain  no  Sulphur. 
— The  sulphur  which  is  contained  in  albumin  is  said  to  he  re- 
moved by  the  alkali  used  in  converting  it  into  alkali  albumi- 
nate, and  it  therefore  differs  from  casein  and  syntonin,  in  both 
of  which  sulphur  is  present.  The  presence  of  sulphur  is  thus 
tested:  Put  a  piece  of  alkali  albuminate  into  liquor  potassa?, 
add  a  drop  of  solution  of  lead  acetate  and  boil.  The  solution 
should  not  become  brown,  as  it  would  do  from  the  formation 
of  lead  sulphide,  if  sulphur  were  present  in  the  alkali  albumi- 
nate. The  sulphur  is,  however,  by  no  means  always  removed 
during  the  preparation,  and  it  is  very  probable  that  a  brown 
color  will  be  got. 

Section  III.— Alteration  of  Albumin  by  Acids.     Acid  Albumin 
or  Syntonin. 

When  a  solution  of  albumin  is  treated  with  very  dilute  acids, 
or  when  solid  albumin  is  dissolved  in  concentrated  acids,  it  is 
converted  into  acid  albumin,  which  is  identical  with  syntonin, 
or,  at  any  rate,  appears  to  be  so.  Myosin,  vitellin,  and  fibrin 
are  quickly  dissolved  by  dilute  acids,  and  converted  into 
syntonin.  It  is  soluble  in  very  dilute  acids,  but  is  insoluble  in 
water,  and  it  is,  therefore,  precipitated  by  neutralization.  It 
is  redissolved  by  excess  of  alkali,  as  it  is  soluble  in  alkalis 
and  alkaline  carbonates.  Unlike  alkali  albuminate,  its  pre- 
cipitation is  not  prevented  by  the  presence  of  alkaline  phos- 
phates. It  is  not  precipitated  from  decidedly  acid  solutions 
by  boiling,  but  when  the  solutions  are  nearly  neutralized,  and 
only  very  faintly  acid,  boiling  precipitates  it. 

1  It  is  usually  stated  that  alkali  albuminate  is  precipitated  by  neutral- 
ization. In  the  text  I  have  made  use  of  this  expression,  which  is  per- 
haps a  convenient  one,  since  the  quantity  of  acid  necessary  to  produce 
precipitation  being  extremely  small  and  the  precipitate  soluble  in  excess, 
the  direction  to  neutralize  rather  than  to  acidulate  is  more  likely  to 
lead  to  the  desired  result,  I  believe  the  student  will  readily  convince 
himself  that  alkali  albuminate  is  not  precipitated  from  its  solutions  by 
exact  neutralization,  and  is  only  thrown  down  when  a  slight  excess  of 
acid  is  present.  I  am  inclined  to  think  that  the  sodium  phosphate  acts 
simply  by  preventing  the  inadvertent  addition  of  a  slight  excess  of  acid, 
which  is  extremely  liable  to  occur  in  solutions  of  alkali  albuminate,  and 
that  syntonin  is  precipitated  by  neutralization  in  presence  of  sodium 
phosphate,  while  alkali  albuminate  is  not,  because  the  point  of  slight 
acidity  at  which  the  albumin  is  precipitated  is  reached  before  that  of 
neutralization  in  the  former  case,  so  that,  before  neutralization  is 
effected,  the  albumin  is  thrown  down  ;  while  in  the  latter,  the  solution 
does  not  become  acid,  and  the  albumin  is  therefore  not  precipitated, 
till  after  neutralization.  On  this  subject  compare  Rollett,  Wien.  Sitz. 
Ber.  XXXIX.  p.  547,  and  Molcschott's  Untersuch,  VII.  p.  230,  also' 
Soxhlet,  Journ.  f.  pract.    Chemie,  N.  F.  1872,  VI.  p.  1. 


BY   DR.    LAUDER   BRUNTON.  433 

**  17.  Preparation  of  a  Solution  of  Acid  Albumin 
or  Syntonin. — Put  some  solution  of  albumin  in  water  into 
a  beaker  and  mix  it  with  its  own  bulk  of  dilute  hydrochloric 
acid  (four  cubic  centimetres  of  strong  commercial  acid  in  one 
litre  of  water).  Pour  some  of  the  mixture  into  several  test- 
tubes.  The  dilute  acid  does  not  convert  the  albumin  immedi- 
ately into  syntonin.  Add  to  the  fluid  in  the  first  test-tube  a 
drop  of  litmus  solution,  and  then  neutralize  it  exactly  with 
dilute  liquor  potassae.  Little  or  no  precipitate  will  fall.  If 
any  should  be  produced,  filter,  and  boil  the  filtrate  or  add  tan- 
nin to  it.  A  copious  precipitate  will  appear,  showing  that 
there  is  much  albumin  in  the  solution.  The  prolonged  action 
of  the  acid  converts  it  into  syntonin,  which  is  precipitated  by 
neutralization.  Let  one  tube  stand  for  some  hours,  and  then 
examine  it,  or  prepare  it  some  hours  before,  and  examine  it 
at  the  same  time  as  the  rest.  Put  a  drop  of  litmus  into  it, 
divide  the  liquid  into  two  parts  and  then  neutralize  one  part 
exactly.  The  whole  of  the  albumin  will  be  precipitated  from 
the  liquid.  To  show  this,  filter  and  boil  the  filtrate;  no  precipi- 
tate will  be  produced.  Acid  albumin  is  not  precipitated  from 
acid  solutions  by  boiliyig.  Boil  the  other  part  of  the  liquid. 
The  albumin  in  it  has  been  already  shown  to  be  converted  into 
syntonin.  No  coagulation  will  occur.  The  formation  of  acid 
albumin  is  accelerated  by  heat.  Warm  a  test-tube  containing 
albumin  solution  mixed  with  acid  gently  to  boiling.  Add  a 
drop  of  litmus  solution,  and  neutralize.  The  albumin  will  be 
completely  precipitated,  and  the  solution,  when  filtered,  will 
give  no  precipitate  on  boiling. 

f  Syntonin  is  precipitated  from  its  solutions  by  neutraliza- 
tion, even  though  alkaline  phosphates  be  present.  Repeat  the 
last  experiment,  adding  a  little  sodium  phosphate  before 
neutralizing.     The  S}rntonin  will  be  precipitated  as  before. 

**  18.  Behavior  of  Syntonin  with  Acids. — Syntonin 
is  solnble  in  concentrated  mineral  acids  ;  it  is  insoluble  in 
them  when  they  are  moderately  dilute,  and  it  is  soluble  in  them 
when  very  dilute. 

Heat  a  watery  solution  of  albumin  gently  to  boiling,  with 
its  own  bulk  of  very  dilute  hydrochloric  or  nitric  acid  (four 
parts  of  commercial  acid  in  1000  of  water).  No  coagulum 
will  be  produced.  Add  a  small  quantity  of  strong  acid  and  a 
precipitate  will  form  which  will  dissolve  in  a  large  quantity  of 
the  acid,  especially  when  heated. 

Put  a  little  serum  albumin  into  three  test-tubes,  and  add  to 
one  concentrated  nitric  acid,  to  another  hydrochloric,  and  to  a 
third  sulphuric  acid.  Dissolve  the  albumin  in  the  acid  by 
heating. 

Dilute  the  solutions  with  twice  their  volume  of  water,  and  a 
precipitate  will  fall.    Let  it  settle,  and  pour  off  the  superna- 
28 


434  ALBUMINOUS    COMPOUNDS. 

tant  liquid  or  filter  it ;  throw  the  precipitate,  still  moist  with 
acid,  into  water,  and  it  will  dissolve.  This  is  not  a  solution  in 
water,  but  in  dilute  acid,  for  a  considerable  quantity  of  acid 
still  remains  in  the  precipitate.  Egg  albumin  differs  from 
serum  albumin  in  its  behavior  with  acids,  and  this,  and  its 
coagulability  by  ether,  form  the  chief  distinctions  between 
them. 

Repeat  the  last  experiment  with  egg  albumin.  It  will  not 
dissolve  so  readily  in  nitric  or  hydrochloric  acid,  and  when 
precipitated  by  dilution  will  dissolve  slowly  and  imperfectly 
in  more  water,  instead  of  doing  so  readily,  like  serum  albumin. 

The  precipitate  from  hydrochloric  acid  will  be  brittle  and 
fibrous  if  the  solution  has  been  recently  made,  but  if  the  solu- 
tion is  boiled  until  it  begins  to  become  violet,  or  allowed  to 
stand  for  some  days,  the  precipitate  will  be  flocculent  and 
soluble,  like  that  of  serum  albumin. 

*  19.  Preparation  of  Syntonin. — (a.)  From  serum  or 
ess;  albumin.  Neutralize  the  solution  in  dilute  acid,  obtained 
in  last  experiment,  with  dilute  liquor  potassa- ;  a  gelatinous 
flocculent  precipitate  of  pure  syntonin  will  fall. 

(&.)  From  fibrin.  Dissolve  it  in  concentrated  hydrochloric 
acid  ;  filter  the  solution  if  necessary,  and  then  proceed  as  with 
serum  albumin. 

(c.)  From  muscle.  Mince  some  muscle,  wash  it  with  water, 
add  to  it  a  considerable  quantity  of  dilute  hydrochloric  acid 
(four  cubic  centimetres  of  strong  acid  to  one  litre  of  water), 
and  let  it  stand  for  several  hours,  stirring  it  frequently.  Fil- 
ter it  through  a  plaited  filter.  Dilute  the  filtrate  with  water, 
neutralize  it  with  a  solution  of  sodium  carbonate,  and  wash 
the  precipitate  with  water. 

20.  Characters. — When  freshly  precipitated,  syntonin 
forms  a  sticky  jell}',  but  it  is  not  tenacious. 

Solubility. — It  is  insoluble  in  water,  and  in  dilute  XaCl 
solution.  It  is  readil}"  soluble  in  lime  water,  in  dilute  hydro- 
chloric acid,  and  weak  alkaline  solutions.  It  is  not  soluble  in 
a  solution  of  six  parts  of  potassium  nitrate  in  100  of  water. 

Its  solutions  behave  like  those  made  by  heating  albuminous 
solutions  with  dilute  acids. 

21.  Tests. — Dissolve  some  syntonin  in  lime-water  and  boil 
it.     Coagulation  will  occur. 

Add  magnesium  sulphate  or  calcium  chloride  to  a  cold  alka- 
line solution  of  syntonin.  Unlike  alkali  albuminate,  it  will 
not  be  precipitated.  Boil  the  solution,  and  precipitation  will 
occur. 

Boil  an  alkaline  solution  of  syntonin,  and  then  add  magne- 
sium sulphate  or  calcium  chloride,  and  a  precipitate  will  fall 
at  once.  This  would  seem  to  be  due  to  the  syntonin  being 
converted  into  alkali  albuminate  bv  boiling. 


BY   DR.    LAUDER    BRUNTON.  435 

22.  Syntonin  contains  Sulphur. — Dissolve  some  syn- 
tonin  in  liquor  potassre,  add  a  drop  of  a  solution  of  lead  acetate 
to  it,  and  boil.  It  will  become  brown  from  the  formation  of 
lead  sulphide. 

23.  Distinction  between  Alkali  Albumin  and  Syn- 
tonin.— If  a  solution  of  alkali  albuminate  contains  an  alkaline 
phosphate,  the  alkali  albumin  is  not  precipitated  when  the 
solution  is  neutralized,  but  syntonin  is  precipitated  from  its 
solutions  b}'  neutralization  whether  an  alkaline  phosphate  be 
present  or  not. 

Synopsis  of  the  Chief  Albumixoes  Bodies.     (Hoppe-Seyler.) 

24.  I.  Albumins. — Albuminous  bodies  which  are  soluble 
in  water,  and  are  not  precipitated  by  very  dilute  acids,  alka- 
line carbonates,  NaCl,  or  platino-hydrocianic  acid.  Their 
solutions  are  coagulated  by  boiling. 

1.  Serum  Albumin. — Not  coagulated  by  shaking  with  ether. 
Readily  soluble  in  concentrated  hydrochloric  acid ;  water 
added  to  this  solution  causes  a  precipitate  which  is  readily 
dissolved  by  more  water. 

2.  Egg  Albumin. — Precipitated  by  ether.  Less  readily  solu- 
ble in  concentrated  hydrochloric  acid  :  water  added  to  this" 
solution  causes  a  precipitate  which  dissolves  with  difficult}*  in 
a  large  quantity  of  water. 

25.  II.  Globulins. — Albuminous  substances,  insoluble  in 
water,  soluble  in  dilute  NaCl  solution.  The  solution  is  coagu- 
lated by  beat.  Very  dilute  hydrochloric  acid  dissolves  them 
and  converts  them  into  syntonin. 

1.  Vitellin. — Not  precipitated  by  the  addition  of  NaCl  in 
substance  to  the  solution  until  it  is  saturated. 

2.  Myosin. — Precipitated  from  its  solution  in  dilute  NaCl 
solution  by  the  addition  of  NaCl  in  substance. 

3.  ttbrinogenic  Substance  and — 

4.  Fibrinoplastic  Substance  {Paraglobulin)  agree  with  myosin 
in  their  reactions,  but  together  in  neutral  solutions  they  form 
fibrin. 

26.  III.  Fibrins. — Insoluble  in  water  or  in  NaCl  solution. 
In  dilute  acids  they  swell,  and  also  in  solutions  of  soda,  though 
to  a  less  extent.     The  swollen  substance  is  coagulated  by  heat. 

27.  IV.  Albuminates. — Insoluble  in  water  or  in  NaCl 
solution.  Easily  soluble  in  very  dilute  hydrochloric  acid  and 
in  alkaline  carbonates.  The  solutions  are  not  altered  by  boil- 
ing. They  are  not  precipitated  from  their  solutions  by  neutrali- 
zation if  alkaline  phosphates  are  present. 

1.  Casein  yicids  potassium  sulphide  when  allowed  to  stand 
with  liquor  potassce,  and  still  more  quickly  when  heated  with  it. 


436  ALBUMINOUS   COMPOUNDS. 

2.  Alkali  albuminates  (Proteins)  do  not  yield  potassium  sul- 
phide with  liquor  potassse. 

28.  V.  Acid  Albumins,  or  Syntonin.— Insoluble  In 
water  or  in  NaCl  solution.  Easily  soluble  in  dilute  hydro- 
chloric acid.  Precipitated  from  solution  by  neutralization, 
even  in  presence  of  alkaline  phosphates. 

29.  VI.  Amyloid. — Insoluble  in  water,  dilute  hydrochloric 
acid  and  sodium  carbonate  ;  in  solutions  of  NaCl  it  does  not 
perceptibly  swell.  It  is  colored  reddish-brown  or  violet  by 
iodine.  It  is  not  digested  by  gastric  juice  at  the  temperature 
of  the  blood. 

30.  VII.  Coagulated  Albuminous  Bodies. — Insoluble  in 
water,  very  dilute  hydrochloric  acid  and  sodium  carbonate;  in 
NaCl  solutions  thejr  do  not  swell  up  perceptibly.  They  are 
colored  yellow  by  iodine.  They  are  readil}'  converted  into 
peptones  by  gastric  juice  at  the  temperature  of  the  blood. 

31.  VIII.  Peptones. — Soluble  in  water,  not  precipitated 
from  the  solution  by  acids,  alkalis,  or  heat. 

33.  Decomposition  of  Albumin. — The  decomposition  of 
albumin  by  various  agencies  is  of  great  interest,  as  it  is  only 
by  a  study  of  the  way  in  which  it  splits  up  that  a  knowledge 
of  its  constitution  can  be  obtained. 

When  treated  with  powerful  oxidizing  agents  albuminous 
bodies  yield  formic,  acetic,  propionic,  butyric,  valerianic,  ca- 
proic,  and  benzoic  acids  and  the  corresponding  aldeli3Tdes,  am- 
monia, and  volatile  organic  bases. 

Such  substances  are,  however,  too  far  removed  from  albumin ; 
it  is  not  from  these  final  products  of  its  decomposition  that 
much  information  is  to  be  got,  but  rather  from  those  bodies  of 
a  tolerably  complex  nature  into  which  it  first  splits  up  when 
treated  with  less  active  decomposing  agents.  These  may  after- 
wards undergo  further  decomposition,  and  yield  substances  of 
a  simple  constitution. 

The  most  important  decomposition  is  that  which  albuminous 
bodies  undergo  when  boiled  with  water  or  with  acids,  or  when 
subjected  to  the  action  of  one  of  the  pancreatic  ferments.  Under 
such  circumstances  peptones  are  first  formed,  and  afterwards 
split  up,  yielding  leucine  and  tyrosine. 

34.  Peptones. — These  are  distinguished  from  other  albu- 
minous bodies  by  not  being  precipitated  by  boiling,  by  alkalis 
or  acids,  nor  by  acetic  acid  and  potassium  ferrocyanide.  They 
are  precipitated  by  alcohol.  Unlike  albumin,  they  diffuse  easily 
through  vegetable  parchment.  With  caustic  potash  and  a 
trace  of  cupric  sulphate,  the}-  give  a  precipitate,  which  dissolves 
on  shaking,  and  forms  a  solution  of  a  red  color,  becoming  violet 
on  the  addition  of  more  copper  sulphate. 

Bodies  which  closely  resemble  the  peptones  formed  during 
digestion  may  be  prepared  by  boiling  albuminous  bodies,  such 


BY    DR.    LAUDER    BRUNTON. 


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438  ALBUMINOUS    COMPOUNDS. 

as  fibrin,  for  along  time  with  water,  especially  under  pressure, 
in  a  Papin's  digester,  in  a  sealed  glass  tube, or  in  a  soda-water 
bottle.  By  boiling  with  dilute  sulphuric  acid  or  concentrated 
hydrochloric  acid,  they  are  produced  in  a  shorter  time.  The 
production  of  peptones  by  the  digestive  ferments  will  be  con- 
sidered a  ft  e  r  w  a  rds. 

35.  Leucine. — Preparation. — It  may  be  obtained  by  boil- 
ing fibrin  with  dilute  acid  for  a  long  time,  or  by  digesting  it 
with  pancreas,  but  it  is  more  usually  got  from  horn  chips. 
Boil  two  parts  of  horn  shavings  with  five  parts  of  sulphuric 
acid,  previously  diluted  with  thirteen  parts  of  water,  for  twenty- 
four  hours,  loss  of  water  by  evaporation  being  prevented  by 
the  arrangement  shown  in  fig.  329.  Saturate  the  fluid  while 
hot,  with  chalk,  filter,  evaporate  the  filtrate  to  half  its  bulk,  add 
oxalic  acid  to  precipitate  the  lime,  filter  and  evaporate  till  a 
scum  forms  on  the  surface,  and  then  set  it  aside  to  crystallize. 
A  considerable  amount  of  tyrosine  will  crystallize  out  first. 
Pour  off  the  liquor,  let  it  stand  till  crystals  of  leucine  form. 
Purify  them  by  boiling  with  water  and  lead  hydrate,  filter,  re- 
move the  lead  by  sulphuretted  hydrogen,  filter,  evaporate  the 
filtrate  in  a  water-bath  to  dryness:  dissolve  the  residue  in  hot 
weak  alcohol,  and  let  it  cool  and  evaporate  till  crystallization 
takes  place. 

Leucine  can  be  formed  synthetically,  and  if  wanted  pure, 
this  is  the  best  way  of  obtaining  it. 

For  this  purpose  a  mixture  of  valeral-ammonia,  hydrocyanic 
and  hydrochloric  acids  are  boiled  together  in  a  retort  till  the 
oil}'  ammonium  compound  has  disappeared.  The  liquid  is  then 
evaporated  to  dryness,  the  residue  is  boiled  with  water  and 
lead  hydrate,  and  the  product  purified  as  already  directed. 

Characters. — Leucine  forms  extremel}"  slender,  white,  glisten- 
ing plates.  Allow  a  drop  of  a  solution  in  water  or  alcohol  to 
evaporate  on  an  object-glass  and  examine  it  under  the  micro- 
scope. It  will  form  round  balls,  which  arc  either  hyaline,  and 
strongly  resemble  fat  globules,  or  exhibit  radiating  lines.  Or 
it  may  appear  as  very  thin  plates  grouped  in  a  radiating  fashion. 
They  differ  from  urates  presenting  a  similar  form  in  not  being 
strongly  refractive. 

Solubility. — 1.  Water:  Pure  leucine  dissolves  slowly,  and  is 
soluble  in  about  twent3*-seven  parts  of  cold  water.  It  dissolves 
more  easily  in  hot  water.  When  impure  it  is  more  easity  solu- 
ble. 

2.  Alcohol:  Pure  leucine  dissolves  in  1040  parts  of  cold, 
and  in  800  of  hot  alcohol.     If  impure,  it  is  much  more  soluble. 

3.  In  Liquor  potassa>,  4,  ammonia,  and  5,  dilute  acids,  it  is 
readily  soluble. 

6.  Concentrated  hydrochloric  or  sulphuric  acids.     It  is  dis- 


BY    DR.    LAUDER    BRUNTON.  439 

solved  without  decomposition.  Neutralize  them,  and  it  is 
precipitated. 

f  Effect  of  Heat. — At  170°  C.  it  sublimes  unchanged  :  a 
higher  temperature  decomposes  it. 

Put  a  little  leucine  into  a  dry  test-tube  and  heat  it  gently. 
It  will  rise  in  white  clouds  and  be  deposited  on  the  cool  part 
of  the  tube.  Heat  the  deposit  strongly  and  a  strong  smell  of 
amylamine  will  be  perceived. 

Decomposition. — When  decomposed  by  heat  it  yields  C02 
XH3,  and  amylamine. 

To  show  this  put  a  portion  of  leucine  into  a  hard  glass  bulb, 
and  connect  this  by  means  of  India-rubber  tubing  with  a  glass 
tube  long  enough  to  reach  to  the  bottom  of  a  test-tube.  Pre- 
pare two  other  similar  pieces  of  glass  tubing  and  three  test- 
tubes,  the  first  of  which  should  be  about  half  filled  with  caus- 
tic baryta  solution,  the  second  with  Nessler's  reagent,  and  the 
third  with  water.  Heat  the  bulb  containing  the  leucine,  apply- 
ing the  heat  first  to  the  upper  part  of  the  bulb  and  gradually 
moving  it  downwards,  so  that  as  the  leucine  sublimes  its  vapor 
may  be  strongly  heated  and  decomposed.  Pass  the  fumes  into 
the  baryta  solution,  then  disconnect  the  glass  tubing,  and  after 
attaching  a  clean  piece,  pass  them  into  Nessler's  reagent  and 
then  into  water.  The  baryta  will  be  precipitated  as  white  car- 
bonate, the  Nessler's  reagent  will  become  brown,  showing  the 
presence  of  ammonia,  and  the  water  in  the  third  test-tube  will 
acquire  the  peculiar  smell  of  amylamine  and  an  alkaline  reac- 
tion. Add  to  the  barium  solution  a  little  nitric  acid.  It  will 
become  clear  and  evolve  gas,  showing  that  the  precipitate  was 
barium  carbonate.  A  minute  quantity  onljr  of  NH3  is  disen- 
gaged when  leucine  is  heated  alone,  and  the  coloration  of  Ness- 
ler's reagent  is  therefore  very  slight.  If  a  little  lime  and  caus- 
tic soda  or  potash  are  heated  with  the  leucine  much  more  NH3 
is  given  off. 

36.  Preparation  of  Nessler's  Reagent. — Dissolve  4 
grammes  of  potassium  iodide  in  250  cub.  cent,  of  distilled 
water.  Set  aside  a  few  cub.  cent,  and  add  a  cold  saturated  solu- 
tion of  mercuric  chloride  to  the  remainder,  till  the  precipitate  of 
mercuric  iodide  is  no  longer  dissolved  on  stirring.  Add  that 
part  of  the  potassium  iodide  solution  which  was  set  aside,  to 
the  rest,  so  as  to  dissolve  the  remaining  precipitate,  and  then 
add  mercuric  chloride  again  very  gradually,  till  a  slight  per- 
manent precipitate  is  produced.  If  a  few  cub.  cent,  of  the 
potassium  iodide  solution  were  not  set  aside,  great  caution 
would  be  required  in  adding  the  mercuric  chloride  so  as  to 
avoid  excess.  Dissolve  150  grammes  of  potassium  hydrate  in 
1  50  'ul).  cent,  of  distilled  water,  allow  the  solution  to  cool,  and 
arid  it  gradually  to  the  potassium  iodide  solution.  Pour  the 
mixture  into  a  measuring-glass  or  flask,  and  add  distilled  water 


440  ALBUMINOUS    COMPOUNDS. 

to  make  up  a  litre.  Pour  it  into  a  large  well-stoppered  bottle, 
taking  care  that  there  is  no  ammonia  near  it  at  the  time.  It 
will  deposit  a  brown  precipitate,  and  become  quite  clear  and 
of  a  pale  greenish-yellow  color.  It  is  then  ready  for  use  ;  a 
little  of  it  should  be  poured  into  a  smaller  bottle  when  wanted. 

37.  Detection  of  Leucine  in  Tissues. — In  order  to  de- 
tect the  presence  of  leucine,  cut  up  the  organ  (the  pancreas  of 
a  sheep  or  ox,  for  example)  into  small  pieces  with  a  large  knife 
or  sausage-making  machine.  Mix  it  with  water  and  let  it  stand 
for  a  little  while,  stirring  it  frequently  ;  filter  it  through  a  piece 
of  cloth,  and  press  out  the  water  first  with  the  hand,  and  then 
with  a  screw-press.  Extract  it  with  water  a  second  time  in  the 
same  way.  Mix  the  watery  extracts  together,  acidify  slightly 
with  acetic  acid,  and  boil,  to  coagulate  the  albumin.  Filter: 
add  a  solution  of  lead  acetate  to  the  filtrate.  Filter:  pass  sul- 
phuretted hydrogen  through  the  filtrate  to  remove  the  excess 
of  lead.  Filter  :  evaporate  the  filtrate  to  dryness.  Extract 
the  residue  with  boiling  alcohol.  Filter:  evaporate  the  filtrate 
to  a  syrup,  and  set  it  aside  for  several  days  to  crystallize.  If 
leucine  is  present,  it  will  crystallize  in  a  day  or  two  in  balls  or 
knots,  or,  possibly,  in  shining  plates,  but  will  not  form  good 
crystals.  It  is  not  pure,  but  is  mixed  with  a  number  of  other 
substances.  In  order  to  free  it  from  these,  the  following  method 
is  recommended  by  Hoppe-Seyler.  Dissolve  it  in  ammonia, 
add  lead  acetate  till  no  further  precipitate  is  produced.  Filter: 
wash  the  precipitate  with  a  little  water.  Suspend  it  in  water, 
and  pass  sulphuretted  hydrogen  through  it.  Filter,  and 
evaporate  the  filtrate  in  the  water  bath. 

38.  Tests  for  Leucine. — The  formation  of  round  lumps  or 
plates  is  not  sufficient  to  prove  that  a  substance  is  leucine,  and 
other  tests  must  be  applied  to  them.  Before  doing  so,  the}' 
should  be  purified  by  drying  them  between  two  folds  of  blot- 
ting-paper, dissolving  them  in  boiling  alcohol,  and  letting  them 
crystallize  out  again.     The  following  tests  may  be  applied: — 

1.  Put  a  portion  into  a  dry  test-tube  and  heat  it  over  a 
Bunsen's  burner  or  spirit-lamp.  If  it  consists  of  leucine,  it 
will  emit  the  smell  of  amylamine. 

2.  Scherer's  Test:  Put  a  small  portion  of  the  supposed 
leucine  with  a  drop  of  nitric  acid  on  a  piece  of  platinum  foil, 
and  evaporate  it  gently.  If  it  is  pure  leucine,  a  colorless, 
almost  invisible,  residue  will  remain  on  the  foil.  Add  a  few 
drops  of  liquor  potassa:  to  it,  and  heat.  It  will  become  yellow 
or  brownish,  and  then  form  an  oily  drop,  which  runs  about 
upon  the  foil  without  adhering  to  it. 

39.  Tyrosine. — Prej>aration. — Boil  horn  shavings  with 
dilute  sulphuric  acid,  crystallize  out  the  tyrosine,  as  directed 
in  the  preparation   of  leucine,  wash  the  crystals  with   cold 


BY    DR.    LAUDER    BRUNTON.  441 

■water,  dissolve  them  in  ammonia,  and  allow  the  solution  to 
evaporate,  until  the  tyrosine  cr3rstallizes. 

It  forms  fine  colorless  microscopic  needles,  with  a  silky 
lustre,  and  without  taste  or  smell. 

Or  digest  fibrin  with  pancreas,  see  §  171. 

Characters. — Let  a  drop  of  a  solution  of  tyrosine  in  hot 
water  evaporate  on  an  object-glass,  and  examine  it  under  the 
microscope.  Long  needle-like  crystals  will  be  seen  which  are 
often  united  in  single  tufts,  or  in  radiating  groups  of  tufts. 

Solubility. — 1.  Cold  water  dissolves  it  with  difficulty.  2. 
Boiling  water  dissolves  it  easily.  Almost  all  the  tyrosine 
crystallizes  out  on  cooling.  It  is  insoluble  in,  3.  Absolute 
alcohol,  4.  Ether.  It  is  easy  soluble  in,  5.  Ammonia,  6.  Liq- 
uor potassse,  7.  Concentrated  solution  of  potassium  or  sodium 
carbonate,  8.  Alcoholic  solution  of  caustic  potash,  9.  Concen- 
trated 113-drochloric  or  sulphuric  acid,  and,  10.  Dilute  mineral 
acid.  11.  Acetic  acid  dissolves  it  with  difficult}'.  12.  Nitric 
acid  dissolves  it.  Let  the  solution  stand  a  while.  A  yellow 
ciystalline  powder  of  nitro-tyrosine  will  separate.  Pour  off  the 
liquid  and  add  liquor  potassse  to  the  powder.  It  will  dissolve 
and  form  a  red  solution. 

40.  Detection  of  Tyrosine. — Treat  the  organ  exactly 
as  described  in  the  process  for  the  detection  of  leucine.  The 
dried  residue,  after  it  has  been  extracted  with  boiling  alcohol 
to  remove  the  leucine,  consists  of  tyrosine.  Dissolve  it  in  boil- 
ing water  or  ammonia,  and  let  it  ciystallize  out. 

41.  Tests  fcr  Tyrosine. — It  is  distinguished  b}r  its  micro- 
scopic appearance,  and  by  the  following  reactions. 

1.  Hoffmann's  Test. — Put  a  little  of  the  solution  supposed 
to  contain  tyrosine  in  a  test-tube  ;  add  some  water,  and  a  few 
drops  of  mercuric  nitrate  solution.  Boil  it  for  a  little  while. 
If  tyrosine  is  present,  the  liquid  will  become  rose-colored,  and 
will  afterwards  deposit  a  red  precipitate. 

2.  Piria's  Test. — Pour  a  few  drops  of  concentrated  sulphu- 
ric acid  on  two  or  three  pieces  of  t3rrosine  the  size  of  a  pin's 
head  in  a  wTatch-glass.  Gently  warm  it  for  a  little.  Let  the 
solution  cool.  Mix  it  with  a  little  water,  and  add  chalk  or 
barium  carbonate  till  all  effervescence  has  ceased.  Filter. 
Evaporate,  if  necessary,  to  a  small  bulk  at  a  gentle  heat,  and 
add  a  few  drops  of  a  neutral  solution  of  ferric  chloride.  The 
fluid  will  become  of  a  beautiful  violet. 

•';.  Scherer's  Test. — Put  a  little  of  the  supposed  tyrosine, 
witli  a  drop  or  two  of  nitric  acid,  on  a  piece  of  platinum  foil, 
and  evaporate  gently.  If  it  is  really  tyrosine,  it  will  quickly 
become  of  a  bright  yellow  color,  and  will  leave  a  deep  yellow 
shining  residue.  Add  a  few  drops  of  liquor  potasses  to  it,  and 
it  will  form  a  yellowish-red  solution.  Evaporate,  and  it  will 
leave  a  brown  residue. 


442  CHEMISTRY    OF    THE    TISSUES. 


CHAPTER  XXXVI. 

CHEMISTRY  OF  THE  TISSUES. 

42.  Epithelial  Tissues. — The  epithelial  tissues — nails, 
hair,  epidermis,  and  epithelium,  as  well  as  horns  and  feathers 
— contain  a  small  quantity  of  fat,  and  a  substance  which  con- 
stitutes the  chief  part  of  their  bulk,  and  to  which  their  form  is 
due.  To  this  substance  the  name  of  keratin  has  been  given. 
It  is  prepared  by  removing  the  fat,  etc.,  from  any  of  the  epi- 
dermal tissues  by  boiling  with  ether,  alcohol,  water,  and  dilute 
acid.  As  the  elementary  anatyses  of  it  do  not  agree,  it  is  rpiite 
possible  that  it  is  a  mixture  of  several  substances,  but  this  is 
not  yet  certainly  made  out.  It  is  nearly  allied  to  albumin,  as 
is  shown  by  its  yielding  the  same  products,  leucine  and  tyro- 
sine, when  decomposed  by  boiling  with  dilute  sulphuric  acid 
(.see  §  35).  It  contains  sulphur,  which  seems  to  be  in  a  very 
loose  state  of  combination.  Hair,  as  is  well  known,  becomes 
blackened  by  lead  sulphide  when  a  leaden  comb  is  used.  To 
show  the  presence  of  sulphur,  put  a  few  parings  of  nails  into 
a  test-tube;  add  a  little  liquor  potassre,  and  boil.  Add  a  little 
hydrochloric  or  sulphuric  acid  to  the  solution  thus  obtained. 
Hydrogen  sulphide  will  be  given  off",  and  may  be  recognized  by 
the  smell. 

43.  Connective  Tissue. — In  the  group  of  tissues  so  desig- 
nated, there  are  several  which  do  not  seem  very  like  one  another. 
Such  are  mucous  tissue,  reticular  and  ordinary  connective  tis- 
sue, adipose  tissue,  cartilage,  bone,  and  dentine.  Their  close 
relation  to  one  another  is  shown  by  their  being  linked  together 
by  intermediate  forms,  by  one  tissue  sometimes  passing  into 
another  so  that  the  boundary  between  them  cannot  be  defined, 
and  \>y  one  occasionally  replacing  another.  Thejr  all  contain 
substances  which*  are  either  derived  from  albumin  or  are  nearl3r 
connected  with  it,  and  have  received  the  name  of  albuminoids. 

44.  Albuminoids. — These  are  nitrogenous,  and  resemble 
albuminous  bodies  in  composition,  but  differ  from  them  in  their 
behavior  with  acetic  acid,  potassium  ferrocyanide,  nitric  and 
hydrochloric  acids.     The}'  are  mucin,  gelatin,  and  chondrin. 

**  45.  Mucin. — This  is  found  in  foetal  connective  tissue, 
and  although  not  present  in  the  fasciculi  is  an  important  con- 
stituent of  tendon  tissue.  It  occurs  also  in  all  mucous  secre- 
tions, and  gives  them  a  tenacious  character.  It  is  distinguished 
by  its  solutions  not  being  coagulated  or  rendered  turbid  by 


EY    DR."   LAUDER    BRUNTON.  443 

boiling ;  by  giving  with  acetic  acid  a  precipitate  which  shrinks 
together  in  pure  acid,  instead  of  swelling  and  dissolving  as 
albuminous  bodies  do.  The  addition  of  potassium  ferrocyanide 
to  the  acetic  acid  prevents  it  from  precipitating  mucin,  so  that 
no  turbidity  is  produced  unless  albuminous  substances  are  also 
present.  It  gives  no  precipitate  with  mercuric  chloride ;  when 
heated  with  liquor  potassas  and  cupric  sulphate,  the  solution 
remains  of  a  clear  blue. 

Preparation,  (a)  From  Saliva?~y  Glands. — Wash  the  sali- 
vary glands  of  an  ox  or  sheep  well.  Cut  them  up  into  small 
pieces.  Wash  away  any  remaining  blood  with  a  little  water. 
Mix  the  glandular  substance  well  up  with  a  considerable  quan- 
tity of  water,  and  filter  through  linen.  Add  acetic  acid  gradu- 
ally to  the  filtrate,  till  a  precipitate  parti}'  fibrous  and  partly 
flocculent  is  obtained.  Filter  through  linen.  Wash  the  pre- 
cipitate with  water,  and  then  with  alcohol  and  ether,  to  remove 
the  fat. 

(b)  From  Tendons. — Free  the  sinews  of  the  legs  of  an  ox  or 
sheep  from  muscle.  Wash  them  well,  and  cut  them  up  in  small 
pieces.  Extract  them  with  water.  Put  them  into  a  large  quan- 
tity of  lime  or  baryta  water,  and  let  them  stand  in  a  closed  ves- 
sel for  several  days.  Filter.  Add  acetic  acid  in  excess  to  the 
filtrate  to  precipitate  the  mucin.  Wash  the  white  flocculent 
precipitate  with  dilute  acetic  acid  and  then  with  dilute  alcohol. 

(c)  From  Ox  Gall.     (See  §  134). 

Solubility. — 1 .  Water : — It  does  not  dissolve,  but  swells  very 
much;  when  the  mixture  is  filtered,  part  of  the  mucin  often 
passes  through,  forming  a  turbid  filtrate.  The  mixture  with 
water  is  not  tenacious,  and  no  foam  is  produced  on  shaking  it. 
2.  XaCl  solution.  Add  a  little  solid  NaCl  to  a  mixture  of 
mucin  and  water.  It  will  become  clearer.  Put  a  glass  rod  into 
the  liquid.  It  will  now  be  found  to  be  tenacious,  and  on  with- 
drawing the  rod  a  long  thread  will  follow  it  from  the  fluid. 
Shake  it,  and  foam  will  form.  Add  a  large  quantity  of  water 
to  the  solution  or  mixture  (for  it  is  not  certain  which  it  is),  and 
the  mucin  will  be  precipitated.  3.  Very  dilute  hydrochloric 
acid  of  less  than  1  per  cent.,  or  other  mineral  acid,  does  not  dis- 
solve mucin.  4.  Dilute  hydrochloric  acid  of  5  per  cent,  partly 
dissolves  it.  Shake  the  solution  and  it  foams.  Add  a  little 
NaCI  to  it,  and  the  mucin  will  dissolve  much  more  readily. 
"i.  Concentrated  hydrochloric,  or  other  mineral  acid,  dissolves 
it  completely.  6.  Liquor  potassae  dissolves  it;  add  a  little  to 
some  mucin,  but  not  enough  to  dissolve  the  whole  of  it.  Filter. 
The  filtrate  is  not  tenacious,  and  is  neutral,  t.  Baryta  and 
limewater  dissolve  mucin,  and  when  used  in  small  quantity 
give,  like  liquor  potassse,  a  neutral  filtrate. 

Precipitation  of  Mucin. — f  1.  Boil  the  neutral  or  slightly 
alkaline  solution.     It  will  not  be  altered. 


444  CHEMISTRY    OF   TIIE    TISSUES. 

f  2.  Add  acetic  acid.  A  precipitate  will  fall.  Let  it  settle. 
Pour  off  the  liquid  and  pour  on  glacial  acetic  acid.  Generally 
it  will  not  dissolve. 

f  3.  Add  acetic  acid  with  solution  of  potassium  ferrocyanide. 
If  the  mucin  is  pure  no  turbidity  will  appear  at  first,  but  will 
do  so  after  the  solution  has  stood  for  some  time. 

4.  Add  mercuric  chloride.     No  precipitate. 

5.  Add  basic  lead  acetate.     A  copious  precipitate  will  form. 
f  Reaction  with  Cupric  Oxide. — Add  liquor  potassre  and  a 

little  cupric  sulphate  to  a  solution  of  mucin.  The  cupric  hy- 
drate will  be  dissolved.  Boil.  The  liquid  will  still  remain  of 
a  clear  blue  color.  This  distinguishes  mucin  from  albumin, 
pepsine,  and  gelatin,  which  give  a  violet  or  red  color. 

**  46.  Ordinary  Connective  Tissue. — Tendons. — 
Gelatigenous  Substance,  or  Collagen. — This  substance 
forms  the  organic  basis  of  bones  and  teeth,  and  the  principal 
or  fibrous  part  of  connective  tissue,  tendons,  ligaments,  and 
fascire. 

Preparation,  (a)  From  Bones Soak  some  bones  in  hydro- 
chloric acid  diluted  with  8  or  9  times  its  bulk  of  water,  chang- 
ing the  acid  several  times.  This  will  remove  the  inorganic 
salts  which  are  deposited  in  the  bone  and  impart  hardness  to 
it;  so  that  when  they  are  entirely  removed,  the  bone  will  retain 
its  original  shape,  but  be  quite  soft  and  pliable.  The  time 
during  which  the  bones  must  be  soaked  in  order  to  remove  the 
whole  of  the  salts  they  contain,  varies  with  their  size  ;  but  if 
the  bones  be  cut  into  small  pieces,  or  thin  bones  such  as  ribs 
are  used,  a  dajr  or  two  is  sufficient.  Wash  them  well  with 
water  to  remove  the  acid  and  dry  them  over  the  water  bath. 

(b)  From  Tendons. — After  removing  the  mucin  from  tendons 
by  means  of  lime  or  baryta  water  {see  §  45),  wash  the  swollen 
pieces  first  with  water,  and  then  with  a  little  acetic  acid  much 
diluted,  so  that  they  contract  and  do  not  again  swell.  Then 
soak  and  wash  them  for  a  while  in  water,  changing  it  several 
times. 

Characters. — When  fresh,  it  is  soft,  but  it  shrinks  and  be- 
comes hard  when  it  is  dried  or  alcohol  is  added  to  it. 

Solubility. — 1.  In  cold  water,  it  will  not  dissolve.  2.  Boil 
the  water.  It  will  dissolve  and  be  converted  into  gelatin. 
On  cooling,  it  will  form  a  jell}'.  3.  In  cold  dilute  acetic  or 
other  acid,  it  will  swell  up.  4.  In  boiling  dilute  acids,  it  is 
dissolved  and  converted  into  gelatin  still  more  readily  than 
b}7  water.  5.  In  hot  liquor  potassae,  it  dissolves  tolerably 
easily. 

47.  Gelatin. — Preparation. — Boil  collagen  obtained  from 
bones  or  siuews  in  the  manner  already  described.  Filter  the 
solution  hot.  Divide  the  filtrate  into  three  parts.  Allow  one 
of  them  to  cool;  it  will  form  a  jelly.     Evaporate  another  to 


BY   DR.    LAUDER   BRUNTON.  445 

dryness  on  the  water  bath.     Use  the  third  for  testing  various 
precipitants. 

Solubility. — 1.  Cold  water.  Dried  gelatin  will  swell,  bnt 
will  not  dissolve.  2.  Boil  the  water,  it  will  dissolve.  3.  Cold 
dilute  acids,  and  4.  Cold  dilute  alkalis,  will  dissolve  it  readily. 

Precipitation. — It  is  precipitated  by  1,  tannic  acid ;  2, 
mercuric  chloride.  Unlike  albumin,  pure  gelatin  is  not  pre- 
cipitated by,  1,  acetic  acid  and  ferrocyanide  of  potassium  ;  2, 
man}'  metallic  salts,  as  lead  acetate,  cupric  or  ferric  sulphate. 
It  is  not  precipitated  by  acids  or  alkalis. 

Alteration  by  Boiling. — Boil  a  solution  of  gelatin  for  some 
time  with  an  acid  or  alkali  and  let  it  cool.  It  will  remain 
fluid  and  will  not  form  a  jelly.  Test  its  reactions.  They  will 
be  found  the  same  as  before.  The  same  effect  is  produced  by 
prolonged  boiling  with  water  alone. 

48.  Elastic  Tissue. — Elastin. — The  elastic  fibres  which 
occur  in  the  connective  tissue  in  various  parts  of  the  bod}", 
and  are  especially  abundant  in  the  middle  coats  of  the  aorta 
and  large  arteries,  and  in  the  ligamentum  nuchas,  and  ligamenta 
subjlava,  are  supposed  to  consist  of  elastin. 

Preparation. — Remove  the  adhering  cellular  tissue  from  the 
fresh  ligamentum  nuchee  of  an  ox.  Cut  it  into  small  pieces, 
and  boil  it  with  alcohol  and  ether  to  remove  the  fat.  Boil  it 
for  24  hours  with  water,  to  dissolve  the  collagen,  renewing  the 
water  as  it  evaporates,  or  preventing  evaporation  (see  §  207). 
Boil  the  residue  with  concentrated  acetic  acid  for  a  consider- 
able time ;  remove  the  acetic  acid  by  boiling  with  water,  and 
then  boil  with  moderately  dilute  liquor  soda?  or  potassre  till  it 
begins  to  swell.  Remove  the  alkali  by  boiling  with  dilute 
acetic  acid,  then  with  water.  Put  the  residue  into  cold  hydro- 
chloric acid  ;  let  it  remain  for  24  hours,  and  then  wash  it  with 
water  till  the  washings  have  no  longer  an  acid  reaction  and 
leave  no  residue  on  evaporation. 

Characters. — The  elastin  which  remains  after  the  treatment 
just  described  is  yellowish  and  elastic  while  moist,  but  when 
dry  becomes  hard  and  brittle. 

Solubility. — 1.  Put  a  piece  of  dry  elastin  in'  water.  It  will 
swell  up  but  will  not  dissolve.  2.  Boil  the  water.  Unlike  the 
collagen  of  connective  tissue,  it  will  not  dissolve.  It  does  not 
form  gelatin,  and  the  water  will  not  gelatinize  on  cooling.  3. 
It  does  not  dissolve  in  alcohol,  ether,  or  acetic  acid,  though  it 
swells  in  the  latter.  4.  Boil  it  with  a  strong  solution  of 
caustic  potash  ;  it  will  dissolve. 

Precipitation. — Neutralize  the  solution  in  potash  with  hy- 
drochloric or  other  acid.  No  precipitate  will  fall.  Add  tannin 
to  the  neutral  solution.  A  precipitate  will  be  produced.  No 
other  acids  cause  a  precipitate. 

Reactions. — 1.  Xanthoprotein  reaction.     Put  a  piece  of  elas- 


440  CHEMISTRY   OF   THE   TISSUES. 

tin  in  concentrated  nitric  acid,  and  let  it  stay  some  time.  It 
will  swell  up,  then  become  yellow,  and  lastly  form  a  mucilagi- 
nous solution.  Add  ammonia,  and  it  will  become  a  deep 
orange-red.     2.  Millon's  reaction.     Test  a  piece  of  elastin  with 

Millon's  reagent.     It  will  become  slightly  red. 

Decomposition. — On  boiling  elastin  with  concentrated  sul- 
phuric acid,  it  is  decomposed  and  yields  leucine,  but  no 
tyrosine. 

**  49. v  Cartilage. — Chondrogen. — The  intercellular  sub- 
stance of  hyaline  cartilage,  and  that  which  lies  between  the 
fibres  of  fibrocartilage,  consists  mainly  of  chondrogen,  so 
named  because  it  is  dissolved  b}'  boiling  in  water  and  forms 
chondrin. 

Solubility. — Take  a  piece  of  costal  cartilage  of  a  sheep  or  ox 
and  test  its  solubilitj'  in  the  following  reagents  :  1.  Cold  water. 
It  is  insoluble.  "When  allowed  to  dry  before  it  is  put  in  water, 
it  swells  up  slightly.  2.  In  boiling  water,  it  dissolves.  On 
cooling,  it  forms  a  jelly.  3.  In  acetic  acid  it  is  insoluble. 
When  dry,  it  swells  very  little  in  acetic  acid. 

50.  Chondrin. — Preparation — Boil  the  costal  cartilages  or 
trachea  of  a  sheep  or  ox  in  water  till  the  perichondrium  strips 
easily  oft",  Bemove  the  perichondrium.  Cut  up  the  cartilages 
into  very  small  pieces,  and  boil  them  with  water  for  several 
hours.  If  a  Papin's  digester  is  at  hand,  boil  them  in  it  under 
a  pressure  of  2-3  atmospheres.  Filter  while  hot.  The  fil- 
trate will  be  strongly  opalescent.  Put  part  of  it  into  a  beaker 
and  allow  it  to  cool.  It  will  form  a  jelly.  To  the  remainder 
of  the  filtrate  add  acetic  acid,  and  the  chondrin  will  be  pre- 
cipitated. 

Solubility. — Test  the  solubility  of  chondrin,  using  either 
that  precipitated  b}r  acetic  acid,  or  the  jelly  which  formed  on 
cooling,  in  the  following  reagents:  1.  In  cold  water  it  is  in- 
soluble. Heat  it,  and  it  is  dissolved.  It  is  soluble  in  2.  Solu- 
tions of  alkaline  salts,  as  sodium  sulphate,  and  is  easily  solu- 
ble in  3.  Dilute  mineral  acids,  4.  Liquor  potassa?,  and  5.  Liquor 
ammoniae.     It  is  insoluble  in  G.  Alcohol,  and  7.  Ether. 

Precipitation. — Add  to  a  warm  solution  of  chondrin  in 
water,  f  1.  Acetic  acid.  It  will  be  precipitated,  f  2.  Add  to 
this  a  little  sodium  chloride  or  sulphate.  The  precipitate  will 
redissolve.  3.  Add  sodium  sulphate  to  a  watery  solution  of 
chondrin,  and  afterwards  acetic  acid.  No  precipitate  will  fall. 
4.  Dilute  hydrochloric  or  other  mineral  acid.  The  chondrin  is 
precipitated  and  is  dissolved  by  excess  of  acid.  5.  Alum  pre- 
cipitates chondrin  ;  excess  dissolves  it.  6.  Lead  acetate,  7.  Sil- 
ver nitrate,  8.  Chlorine  water,  all  precipitate  chondrin. 

Effect  of  Boiling. — Boil  a  watery  solution  of  chondrin  for  a 
long  time.     Let  it  cool,  and  it  will  be  found  to  have  lost  its 


BY   DR.    LAUDER   BRUNTON.  447 

power  of  gelatinizing,  but  it  will  give  the  other  reactions  just 
as  before. 

Decomjiosition  of  Ghondrin. — By  boiling  with  concentrated 
hydrochloric  acid,  chondrin  is  decomposed,  and  yields  grape 
sugar,  and  certain  nitrogenous  substances.  The  presence  of 
grape  sugar  may  be  tested  by  the  reactions  given  in  §  17 
or  §  155. 

51.  Distinctive  Characters  of  Mucin,  Chondrin, 
Gelatin,  and  Albumin. 

Mucin. — Precipitated  by  acetic  acid,  the  precipitate  is  not 
dissolved  by  sodium  sulphate. 

Chondrin. — Precipitated  by  acetic  acid,  the  precipitate  is 
dissolved  by  sodium  sulphate. 

Gelatin. — Not  precipitated  by  acetic  acid,  nor  by  acetic  acid 
and  potassium  ferrocyanide. 

Albumin. — Dissolved  by  acetic  acid,  the  solution  is  precipi- 
tated b}'  potassium  ferrocyanide,  or  by  the  addition  of 
alkaline  salts  and  heat. 

Gelatin  and  Chondrin  are  most  generally  recognized  by  their 
hot  solutions  forming  a  jelly  on  cooling ;  but  as  they  are  both 
deprived  of  this  property  by  long  boiling  or  boiling  with  acids, 
this  test  is  not  always  to  be  depended  on. 

**  52.  Bone. — When  bone  is  subjected  to  the  action  of 
acids,  the  earthy  salts  are  removed.  The  remainder,  to  which 
the  name  ossein  has  been  given,  consists  chiefly  of  gelatigenous 
substance.  The  earthy  salts  are  tribasic  calcium,  and  magne- 
sium phosphates,  calcium  carbonate,  and  small  quantities  of 
calcium  fluoride. 

To  remove  the  earthy  salts,  and  leave  the  ossein,  place  a  bone 
for  some  time  at  a  low  temperature  in  very  dilute  hydrochloric 
acid.  When  treated  with  warm  dilute  hydrochloric  acid,  bone 
gives  out  CO.,  and  is  apt  to  separate  into  lamellae.  The  ossein 
is  soft,  flexible,  and  elastic  while  moist,  but  becomes  hard 
when  dry.  It  retains  the  form  of  the  bone.  In  its  chemical 
characters  it  resembles  the  arelatisenous  substance  from  con- 
nective  tissue. 

To  get  the  earthy  salts,  incinerate  the  bone,  when  the  organic 
substance  will  be  consumed,  and  they  will  remain  behind,  mixed 
with  other  salts  formed  during  the  combustion,  for  here  as  in 
other  cases  the  salts  in  the  ash  differ  considerably  from  those 
which  exist  in  the  tissue. 

**  53.  Adipose  Tissue. — Fats. — Fats  differ  from  each 
other  in  appearance  and  consistence.  Their  general  properties 
may  be  conveniently  studied  in  olive  oil,  for  which  cod  liver  oil 
or  train  oil  may  be  substituted,  if  an  animal  fat  is  desired. 

8olubility^—F&tB  are  insoluble  in  1.  Water,  and  2.  Cold  al- 
cohol, f  3.  Hot  alcohol.  Warm  a  test-tube  containing  oil 
and  alcohol  over  a  spirit-lamp  or  Bunsen's   burner.     As  the 


448  CHEMISTRY    OF   THE    TISSUES. 

spirit  becomes  warm,  part  of  the  oil  will  be  dissolved.  Pour 
off  some  of  the  clear  alcoholic  solution  into  another  tube  and 
cool  it.  It  will  become  milky  from  tin-  deposition  of  oil.  f  4. 
Cold  ether.  Shake  a  little  oil  wit h  ether  and  it  will  dissolve 
readily.  The  test-tube  containing  the  ether  must  not  he 
brought  near  a  flame,  as  its  vapor  is  readily  inflammable.  ;">. 
Chloroform  ;  6.  Oil  of  turpentine,  and  other  volatile  oils,  also 
dissolve  fat  readily. 

*  JEmulaionizing  of  Fats. — Shake  a  little  oil  with  a  solution 
of  albumin  in  a  test-tube.  The  oil  will  become  finely  divided, 
and  form  a  milky-looking  fluid  or  emulsion.  Put  a  drop  of 
this  under  the  microscope,  and  it  will  be  found  to  consist  of 
minute  globules  of  fat.  The  globules  in  the  emulsion  unite 
again  and  form  large  globules,  but  very  slowly.  Add  a  little 
acetic  acid  to  the  emulsion  and  shake  it.  The  globules  will 
unite  much  more  quickly.  Repeat  the  experiment  with  a  solu- 
tion of  gelatin.     This  also  will  emulsionize  the  fat. 

Reaction. — Wash  a  piece  of  lard  in  water  and  press  a  piece 
of  litmus  paper  against  it,  or  melt  it  in  a  test-tube,  and  put  a 
drop  of  it  or  of  olive  oil  on  the  paper.  Its  reaction  will  be 
neutral. 

Composition  of  Fats. — Fat  consists  of  a  triatomic  radicle, 
propenyl  or  glyceryl,  combined  with  three  atoms  of  a  mona- 
toinic  fatty  acid.  The  glyceryl  may  be  displaced  by  inorganic 
bases,  such  as  potassium,  lead,  etc.,  and  glyceryl  hydrate,  or 
glyceryl  alcohol  (glycerin)  is  produced.  The  replacement  of 
glycerin  by  other  basis  is  termed  saponification. 

Boil  two  and  a  half  grammes  of  olive  oil  with  one  gramme 
of  very  finely  powdered  lead  oxide,  and  about  fifty  cubic  centi- 
metres of  water  in  a  beaker  or  evaporating  dish  for  some 
hours,  stirring  the  mixture  well  to  prevent  the  lead  oxide  from 
falling  to  the  bottom,  and  replacing  the  water  as  it  evaporates. 
The  lead  will  combine  with  the  fatty  acid  in  the  oil,  forming  a 
slightly  yellowish  mass,  and  the  glycerin  will  be  set  free.  To 
obtain  the  glycerin,  filter  the  fluid  ;  pass  sulphuretted  l^drogen 
through  the  filtrate,  add  a  little  animal  charcoal  to  decolorize 
it;  let  it  stand  for  a  while  in  a  warm  place  ;  filter  and  evapo- 
rate the  filtrate. 

54.  Glycerin. — Gl3"cerin  is  a  S}*rup3-  fluid,  with  a  sweet 
taste  and  a  neutral  reaction. 

Solubility. — 1.  With  water,  and,  2,  with  alcohol,  it  mixes 
very  readily.     3.  With  ether  it  does  not. 

Solvent  Foiver — It  dissolves  many  metallic  oxides.  Add  a 
little  liquor  potassae  to  a  solution  of  copper  sulphate  or  lead 
acetate,  a  precipitate  will  fall.  Add  a  little  glycerin,  and  the 
precipitate  will  redissolve. 

It  also  acts  to  some  extent  as  a  solvent  for  fatty  acids. 

Decomposition. — Put  a  little  glycerin,  free  from  water,  into 


BY   DR.   LAUDER   BRUNTON.  449 

.1  test-tube,  with  glacial  phosphoric  acid  or  acid  potassium 
sulphate,  aud  heat.  The  glycerin  will  be  decomposed,  aud  yield 
water  and  acrolein  or  acrol,  a  body  which  has  an  extremely 
unpleasant  smell,  and  causes  great  irritation  of  the  nose  and 
eyes. 

Test  for  Glycerin. — As  no  other  body  yields  acrolein  when 
decomposed  in  the  way  just  mentioned,  its  formation  serves  as 
a  test  for  glycerin ;  and  as  it  is  very  pungent,  small  quantities 
of  glycerin  can  easil}'  be  detected. 

55.  Muscle. — For  the  structure  of  muscle,  see  Chap.  IV. 
Reaction. — Muscles  which  have  been  at  rest  have  an  amphi- 

cromatic  reaction ;  i.  e.,  they  change  red  litmus  to  blue,  and 
also  blue  litmus  to  red.  They  do  not  alter  the  color  of  blue 
litmus  so  much  as  that  of  red,  and  they  are  therefore  alkaline. 
Alteration  in  the  Reaction  by  Contraction. — The  reaction 
changes  to  acid  after  contraction  of  the  muscle  or  after  death. 
See  Chap.  XX.,  Obs.  YI. 

56.  Composition  of  Muscle. — The  Sarcolemma  is 
usually  said  to  agree  with  elastic  tissue  in  its  characters,  and 
to  yield  no  gelatin,  but  it  has  been  recently  stated  to  be  solu- 
ble, though  slowly,  in  alkalies  and  acids,  as  well  as  in  gastric 
juice,  and  would  thus  more  nearly  resemble  connective  tissue. 

51.  Sarcous  Elements. — Little  is  known  regarding  the 
chemical  composition  of  the  sarcous  elements,  except  that 
they  swell  slightly,  and  lose  their  power  of  double  refraction 
when  boiled  or  when  heated  with  alkalies  or  very  dilute  acids. 
Alcohol  does  not  alter  them. 

f  58.  Muscle  Plasma. — When  muscles  are  subjected  to 
pressure  at  0°  C,  a  fluid  termed  muscle  plasma  is  obtained. 
The  plasma  of  muscles  resembles  the  plasma  of  the  blood,  in 
possessing  the  power  of  coagulating  spontaneously,  and  sepa- 
rating into  a  clot,  and  serum.  To  this  clot,  corresponding  to 
the  fibrin  of  the  blood,  the  name  myosin  has  been  given.  Co- 
agulation of  the  plasma  causes  the  muscles  to  lose  their  elas- 
ticity and  become  stiff  and  hard,  and  thus  gives  rise  to  rigor 
mortis.  After  some  time,  decomposition  sets  in,  and  the  mus- 
cles again  become  soft  and  flexible.  Muscle  plasma  is  some- 
what troublesome  to  obtain,  as  it  coagulates  too  quickly  in  the 
muscles  of  warm-blooded  animals  to  allow  of  its  preparation 
from  them,  and  the  muscles  of  frogs,  in  which  it  coagulates 
more  slowly,  are  not  always  to  be  had  in  sufficient  quantity. 

Preparation. — Prepare  a  freezing  mixture  by  mixing  to- 
gether equal  parts  of  salt  and  snow,  or  pounded  ice.  Intro- 
duce it  into  a  large  beaker,  and  plunge  a  platinum  crucible  or 
small  tin  box  into  it.  Fill  another  beaker  with  half  per  cent, 
salt  solution,  and  put  it  in  a  vessel  containing  snow  or  ice. 
Prepare  several  frogs  in  the  following  manner:  Open  the  thorax, 
cut  off  the  apex  of  the  heart,  push  a  canula  up  into  the  aortic 
29 


450  CHEMISTRY    OF. THE    TISSUES. 

bulb,  and  inject  a  half  percent,  salt  solution  through  it,  in  the 
manner  directed  tor  artificial  circulation  in  Chap.  XVI.  §  I-"'. 
till  the  fluid  which  issues  from  the  veins  is  quite  colorless. 
Cut  away  the  muscles  close  to  their  attachments,  and  wash 
them  with  half  per  cent,  salt  solution  cooled  to  0°  C.  When 
washed,  squeeze  them  tightly  together  into  a  ball,  and  tie  them 
up  in  a  piece  of  thin  linen  ;  put  them  into  the  crucible  or  tin 
box.  As  the  muscles  of  each  frog  are  prepared  add  them  to 
those  in  the  crucible,  and  let  it  remain  in  the  freezing  mixture 
until  they  are  all  frozen  quite  hard.  Take  a  sharp  knife  and 
cool  it  in  the  freezing  mixture;  cut  the  frozen  mass  of  muscle 
into  very  thin  slices;  throw  them  into  a  mortar  cooled  in  the 
same  way,  and  break  them  up  small.  Tie  them  up  in  a  piece 
of  strong  linen,  and  put  them  into  a  strong  screw-press.  As 
the  temperature  of  the  muscle  is  gradually  raised  by  the 
warmth  of  the  room  to  0°  C,  the  frozen  plasma  melts  and 
issues  from  the  press.  It  must  be  collected  in  a  vessel  cooled 
in  ice,  and  filtered  through  paper  moistened  with  cold  half  per 
cent,  salt  solution,  and  collected  in  a  cold  beaker.  The  funnel 
may  be  kept  cold  during  filtration  by  placing  it  in  a  double  cop- 
per filtering  stand  of  the  form  shown  in  fig.  336,  but  filled  with 
snow  or  pounded  ice,  instead  of  hot  water.  As  the  filters  get 
soon  choked,  they  must  be  frequently  renewed.  The  filtered 
plasma  is  a  slightly  yellowish  and  opalescent,  syrupy,  but  not 
tenacious,  fluid. 

Reaction. — Its  reaction  is  alkaline,  like  that  of  muscle. 

Coagulation  of  Muscle  Plasma. — Transfer  a  little  plasma 
from  the  beaker  to  cooled  test-tubes  and  observe  the  following 
facts : — 

It  will  coagulate  spontaneously  when  allowed  to  stand  at 
the  temperature  of  the  room,  and  form  a  gelatinous  clot,  which 
will  begin  at  the  sides  of  the  tube,  and  extend  inwards. 

B}'  stirring,  a  coagulum  is  obtained,  which  is  flocculent,  and 
not  fibrous  like  the  fibrine  of  blood. 

Heat  greatly  accelerates  its  coagulation,  and  at  40°  C.  it 
coagulates  almost  instantaneous^. 

Cold  water  coagulates  it  at  once,  so  that  the  plasma  when 
dropped  into  it,  forms  white  elastic  balls.  Cold  NaCl  solution, 
of  fifteen  per  cent.,  also  coagulates  it,  but  a  solution  of  five 
per  cent.,  does  not.  Dilute  hydrochloric  acid  of  ten  per  cent, 
coagulates  it  at  once,  but  dissolves  the  coagulum,  and  forms 
syntonin  almost  immediately. 

**  59.  Examination  of  the  Aqueous  Extract  of 
Muscle. — In  order  to  obtain  an  aqueous  extract  of  muscle,  a 
dog  must  be  killed  by  decapitation,  and  the  blood  removed 
from  the  vessels  of  the  lower  extremities  by  artificial  circula- 
tion. For  this  purpose  open  the  abdomen  quickly,  and  insert 
a  canula  iu  the  aorta.     Inject  ten  per  cent.  NaCl  solution  into 


BY   DR.    LAUDER    BRUNTON.  451 

it  till  the  blood  returns  colorless  by  the  vena  cava.  Cut  off 
some  of  the  muscles  of  the  thigh  quicklj",  and  mince  them  up 
small.  This  is  best  done  by  a  sausage-making  machine.  Mix 
the  mass  with  distilled  water,  stir  it  up  well,  and  let  it  stand 
for  a  quarter  of  an  hour.  Filter  it  through  linen,  aiding  its 
filtration  by  pressure. 

**  60.  Albuminous  Substances  in  Muscle. — Alkali 
Albuminate. — The  watery  extract  thus  obtained  contains 
alkali  albuminate.  It  is  at  first  alkaline  or  neutral,  but  after- 
wards becomes  acid,  and  the  alkali  albuminate  is  then  thrown 
down  as  a  flocculent  precipitate.  The  source  of  the  acid  is 
not  known.  If  the  extract  has  been  made  from  muscle  which 
has  already  become  acid,  this  precipitate  will  not  fall. 

To  a  portion  of  the  extract  add  dilute  hydrochloric,  acetic, 
or  lactic  acid  very  gradually.  A  flocculent  precipitate  will 
fall. 

Repeat  the  last  experiment,  using  exactly  the  same  quanti- 
ties of  extract  and  acid,  but  add  a  little  sodium  phosphate  to 
the  extract  before  acidulating  it.  No  precipitate  will  fall. 
See  §  15. 

Albumins. — Besides  alkali  albuminate,  the  extract  contains 
two  other  albuminous  substances,  one  of  which  coagulates  at 
45°  C,  the  other  at  75?  C.  Filter  the  fluid  from  which  the 
alkali  albuminate  has  been  precipitated  either  by  the  develop- 
ment or  the  addition  of  acid.  Put  some  in  a  test-tube  and 
warm  it  in  a  water  bath  to  45°  C.  A  precipitate  will  form. 
The  coagulation  is  not  affected  at  all  by  previously  rendering 
the  liquid  neutral  or  alkaline.  Let  the  fluid  stand  till  the 
precipitate  subsides,  and  then  remove  it  by  filtration,  and 
warm  the  filtrate  to  70°  C.  A  second  coagulation  will  take 
place. 

**  61.  Myosin. — Free  the  remainder  of  the  muscles  from 
fascia,  tendons,  fat,  nerves,  and  vessels,  and  cut  them  up  small. 
Put  the  mass  of  finely-divided  muscle  into  five  or  six  times 
its  weight  of  water  and  stir  it  well.  Let  it  stand  for  several 
hours  and  then  strain  it  through  a  linen  cloth,  and  express 
the  fluid  with  the  aid  of  a  screw-press.  Treat  the  muscles  a 
second  time  with  water  in  the  same  way,  and  strain  and  press 
again.  Unite  all  the  fluids  thus  obtained  and  keep  them  for 
examination.  Wash  the  muscle,  which  remains  on  the  linen, 
with  water,  as  before,  till  it  becomes  of  a  grayish  color,  and 
the  water  is  no  longer  colored. 

Throw  it  into  a  mortar,  and  rub  it  up  with  ten  per  cent,  salt 
solution  in  sufficient  quantity  to  prevent  it  from  being  too 
thick  and  to  allow  it  to  flow  tolerably  easily.  Let  it  stand  for 
several  hours ;  filter,  first  through  linen,  then  through  paper, 
and  add  to  the  filtrate  several  pieces  of  rock  salt.  As  the  salt 
dissolves, the  myosin,  which  is  insoluble  in  a  concentrated  NaC 


452  CHEMISTRY   OF   THE   TISSUES. 

solution  is  precipitated  in  flocculi.  If  any  salt  remains  undis- 
solved after  the  myosin  seems  fully  precipitated,  remove  it,  and 
then  filter  the  solution.  The  myosin  which  contains  a  large 
amount  of  NaCl  remains  on  the  filter.  In  order  to  free  it  from 
this,  dry  it  as  well  as  possible  by  pressing  it  between  folds  of 
filtering  paper  ;  dissolve  it  in  a  little  water,  and  throw  the  solu- 
tion into  a  large  beaker  full  of  water,  when  it  will  again  be  pre- 
cipitated. Let  it  stand  for  a  day,  pour  off  the  clear  fluid  as  well 
as  possible,  and  then  collect  the  precipitate  on  a  filter.  After 
the  greater  part  of  the  water  has  passed  through  the  filter,  but 
while  the  precipitate  is  still  moist,  remove  it  into  a  beaker,  as 
it  cannot  be  separated  from  the  filter  after  it  becomes  dry. 

Solubility. — Test  the  solubility  of  the  moist  myosin  in  the 
following  reagents :  f  1.  Ten  per  cent.  NaCl  solution.  The 
myosin  will  dissolve.  Put  some  sodium  chloride  in  substance 
into  the  solution.  As  it  dissolves,  and  the  solution  becomes 
saturated,  the  myosin  will  be  precipitated.  It  is  soluble  in  2. 
Solution  of  sodium  sulphate  or  other  neutral  salt ;  3.  Very 
dilute  liquor  potassa? ;  and  4.  Very  dilute  h}-drochloric  acid. 

Action  of  Acids  and  Alkalies. — Dilute  acid  and  alkalies  dis- 
solve myosin,  as  has  just  been  seen.  At  first  it  is  simply  dis- 
solved, but  is  very  soon  converted  into  acid  albumin  or  alkali 
albuminate.  Divide  the  solutions  of  myosin  in  dilute  liquor 
potassoe  and  dilute  lrydrochloric  acid  just  made,  into  two  por- 
tions, add  salt  solution  immediately  to  one  portion  of  each,  put 
in  a  drop  of  litmus,  and  neutralize  both.  No  precipitate  will 
fall,  for  the  myosin  being  unchanged  is  soluble  in  the  salt  solu- 
tion. Let  the  other  portions  stand  for  ten  minutes,  and  then 
treat  them  in  the  same  way.  A  precipitate  will  fall  on  neutral- 
izing them,  for  the  myosin,  being  now  converted  into  alkali  al- 
buminate and  syntonin,  is  no  longer  soluble  in  NaCl  solution. 

Coagulation  of  Myosin. — 1.  Boil  a  NaCl  solution  of  myosin  ; 
it  will  coagidate.  2.  Add  alcohol  to  its  NaCl  solution,  and  a 
similar  coagulum  will  form. 

Effect  of  Drying. — Dried  myosin  is  tough  and  difficult  to 
powder,  and  almost  insoluble  in  NaCl  solution. 

**  62.  Extractive  Matters  in  Muscle.— The  cold 
watery  extract  of  muscle  contains,  beside  the  albuminous  mat- 
ters, creatine,  creatinine,  hypoxanthine  (sarkin),  xanthine,  uric 
acid,  inosic  acid  (apparently  not  always  present),  glucose,  ino- 
site,  salts  of  lactic  acid,  and  volatile  fatty  acids  and  acid  phos- 
phates of  the  alkalies.  Unless  a  large  quantity  of  muscle  can 
be  got,  it  will  be  better  to  use  Liebig's  extract  for  the  prepara- 
tion of  these  substances.  Put  the  wateiy  extract  of  muscle  in 
a  tin  kettle;  heat  it  quickly  to  boiling,  so  as  to  coagulate  the 
albumin.  Filter  it  through  a  linen  cloth.  Let  the  filtrate  be- 
come quite  cool,  and  add  acetate  of  lead  to  it  as  long  as  a  pre- 
cipitate is  formed.     Excess  of  lead  must  be  avoided  as  much  as 


BY    DR.   LAUDER   BRUNTON.  -         453 

possible.    Collect  the  precipitate  on  a  filter,  and  keep  it  for  after 
examination.  .  ......         (a) 

63.  Creatine. — Precipitate  any  lead  present  in  the  filtrate 
b}'  hydrogen  sulphide :  filter ;  evaporate  the  filtrate  to  a  thin 
syrup  on  the  water-bath.  Put  it  in  a  cool  place  for  several 
daj's,  and  the  creatine  will  separate  in  short  colorless  crystals. 
Let  it  stand  till  no  more  crystals  are  deposited ;  pour  off  the 
mother  liquor  from  the  crystals,  and  add  to  it  two  or  three  times 
its  volume  of  alcohol  of  88  per  cent.,  so  as  to  cause  the  sus- 
pended creatine  to  be  deposited.  Filter  it,  and  wash  the  crys- 
tals with  a  little  alcohol.  Wash  off  the  crystals  which  still  re- 
main on  the  evaporating  dish  with  the  alcohol  which  drops 
from  the  filter,  throw  them  also  on  the  filter,  and  wash  them 
with  a  little  alcohol.  Collect  the  filtrates,  mix  them  and  put 
them  aside.      .........         (b) 

Dissolve  the  ciystals  in  a  little  boiling  water,  and  allow  the 
solution  to  cool,  when  the  creatine  will  crystallize  out  in  color- 
less transparent  and  lustrous  oblique  rhombic  prisms,  which, 
when  gently  heated  on  a  piece  of  platinum  foil,  lose  water  of 
crystallization,  and  become  dull  and  whitish. 

Solubility. — Creatine  is  sparingly  soluble  in  cold  water ; 
easiby  soluble  in  boiling  water  ;  almost  insoluble  in  strong  alco- 
hol ;  insoluble  in  ether. 

Reaction. — The  solution  in  hot  water  has  a  neutral  reaction, 
and  bitter  taste. 

Test. — Creatine  has  no  very  characteristic  reactions,  and  it 
is  best  recognized  by  converting  it  into  creatinine.  If  it  is 
pure,  no  precipitate  will  fall  on  the  addition  of  zinc  chloride  to 
its  solutions,  but  if  mixed  with  creatinine  a  precipitate  will  be 
produced. 

Decomposition. — When  it  is  boiled  for  a  considerable  time 
with  caustic  baryta,  creatinine  decomposes  into  urea  and  sar- 
cosin.  If  the  boiling  is  continued  still  longer,  the  urea  decom- 
poses into  carbonic  acid  and  ammonia.  This  reaction  is  very 
interesting  as  indicating  one  source  of  urea  in  the  body.  When 
boiled  with  water  for  a  long  time  or  with  acids,  it  loses  water 
and  is  converted  into  creatinine. 

64.  Creatinine. — Boil  creatine  for  half  an  hour  with  dilute 
hydrochloric  acid  ;  neutralize  with  h}*drated  lead  oxide  ;  filter  ; 
evaporate  the  filtrate  to  dryness  on  the  water-bath.  Extract 
the  residue  with  alcohol,  and  evaporate  the  extract.  The  crea- 
tinine will  crystallize  in  colorless  lustrous  prisms,  which,  when 
heated  on  platinum  foil,  do  not  dry  like  creatine. 

Solubility. — It  is  soluble  in  water,  especially  when  hot.  Un- 
like creatine,  it  is  soluble  in  hot  alcohol. 

Reaction. — Test  the  watery  solution  with  litmus  or  turmeric 
paper  ;  it  will  be  found  strongly  alkaline.  It  has  a  taste  like 
dilute  ammonia. 


454  CHEMISTRY    OF    THE    TISSUES. 

Characters. — Creatinine  nets  like  a  strong  alkali,  and  forms 
double  salts  with  metals.  Themosl  importanl  is  its  compound 
with  zinc  chloride.  Add  to  an  alcoholic  or  not  very  dilute 
watery  solution  of  creatine,  a  concentrated  Byrupy  solution  of 
zinc  chloride  free  from  hydrochloric  acid  ;  a  precipitate  of 
warty  granules  will  fall  at  once  if  the  solution  is  concentrated  : 
but  if  dilute,  groups  of  needles  will  slowly  form.  The  granules 
are  seen  under  the  microscope  to  consist  of  radiating  groups 
of  fine  needles.  They  are  very  sparingly  soluble  in  cold  water  ; 
more  so  in  hot ;  insoluble  in  alcohol ;  but  very  soluble  in  mine- 
ral acids. 

This  test  is  sufficient  to  distinguish  creatinine.  It  is  fur- 
ther precipitated  by  silver  nitrate,  by  mercuric  chloride,  and 
by  mercuric  nitrate  with  the  gradual  addition  of  sodium  carbo- 
nate. 

65.  Sarkin  (Hypoxanthine). —  Evaporate  the  alcohol 
from  the  filtrate  (b)  upon  the  water-bath  ;  dilute  it  with  water  ; 
render  it  alkaline  by  ammonia,  and  then  add  an  ainmoniacal 
solution  of  silver  nitrate.  Sarkin  will  be  precipitated.  Let  the 
flocculcnt  precipitate  subside  ;  wash  it  several  times  by  decan- 
tation  with  water  containing  ammonia;  throw  it  on  a  smooth 
porous  filter,  and  wash  it  thoroughly  ;  push  a  glass  rod  through 
the  bottom  of  the  filter,  and  wash  the  precipitate  with  nitric 
acid  of  1.100  sp.  gr.  into  a  small  Bask.  Heat  it  to  boiling,  and 
add  more  nitric  acid  till  the  whole  is  dissolved.  The  fluid 
should  be  kept  nearly  boiling.  Sometimes  a  few  flakes  of 
silver  chloride  remain  undissolved.  Decant  the  liquid  from 
them  into  a  beaker,  and  let  it  stand  for  six  hours.  A  double 
nitrate  of  silver  and  hypoxanthine  will  crystallize  out. 

Decant  the  liquid  (c)  from  the  crystals  and  preserve  it  for 
the  preparation  of  xanthine.  Wash  them  with  an  ammoniacal 
solution  of  silver  nitrate  to  remove  the  free  acid.  Suspend  them 
in  water,  and  pass  hydrogen  sulphide  through  it.  Filter  from 
the  silver  sulphide,  and  evaporate  the  filtrate.  The  hypoxan- 
thine  will  crj-stallize  out. 

In  its  reactions  it  resembles  xanthine,  but  differs  from  it  in 
being  precipitated  by  silver  nitrate. 

66.  Xanthine. — To  the  mother  liquor  (c)  of  the  hypoxan- 
thine add  ammonia  in  excess.  A  flocculent  precipitate  of  nitrate 
of  silver  and  xanthine  will  fall.  Wash  it  by  decantation  ;  sus- 
pend it  in  boiling  water,  and  decompose  it  by  hydrogen  sul- 
phide. Filter  and  evaporate.  The  xanthine  will  separate  as  a 
scaly  film. 

I'ests. — Put  a  little  xanthine  in  ammonia.  It  will  dissolve. 
Add  a  little  nitric  acid  to  a  portion  of  xanthine  in  a  porcelain 
capsule;  evaporate  to  dryness.  A  yellow  residue  will  remain. 
Add  a  drop  of  caustic  soda  to  it,  and  it  will  become  red.  Heat 
it,  and  the  color  will  change  to  purple  red. 


BY    DR.    LAUDER    BRUNTON.  455 

Put  liquor  soda?  in  a  watch-glass  with  a  little  chloride  of 
lime  ;  stir  it,  and  introduce  a  portion  of  xanthine.  A  ring  will 
form  round  it,  at  first  dark  green,  but  soon  becoming  brown, 
and  then  disappearing. 

67.  Uric  Acid. — Suspend  the  lead  precipitate  (a)  in  water ; 
decompose  it  complete^  by  hydrogen-sulphide  ;  filter;  concen- 
trate the  filtrate  in  a  water-bath.  Uric  acid  will  separate  gradu- 
ally. 

Filter,  and  set  the  filtrate  aside  (d).  Wash  the  crystals  on 
the  filter  with  a  little  water  and  then  with  alcohol.  If  desired, 
they  may  be  further  purified  by  dissolving  them  in  a  little 
liquor  sodae,  precipitating  by  ammonium  chloride  ;  filtering  and 
decomposing  by  dilute  hj-drochlorie  acid. 

Jfurexide  Test. — Put  a  small  portion  of  uric  acid  on  a  watch- 
glass,  with  one  or  two  drops  of  nitric  acid,  and  evaporate  to 
dryness  at  a  moderate  temperature.  A  yellow  residue  will  re- 
main, which  becomes  red  when  quite  dry.  Put  a  drop  of  am- 
monia on  the  side  of  the  glass,  and  let  it  run  gently  down  to 
the  uric  acid,  which  will  then  become  of  a  beautiful  purple.  If 
a  drop  of  liquor  potassre  or  liquor  sodas  is  used  instead  of  am- 
monia, a  bluish-violet  color  will  be  produced. 

Inosite. — Evaporate  the  filtrate  (d)  till  a  permanent  tur- 
bid it}r  is  produced  by  the  addition  of  alcohol.  Then  add  its 
own  volume  of  alcohol  to  it  and  warm  it,  when  the  turbidity 
will  disappeai*.  Set  it  aside  for  several  days.  Inosite  ma}' 
then  crystallize  out.  If  it  does  not,  add  ether ;  and  if  still  no 
crystals  form,  evaporate  almost  to  dryness  ;  add  a  little  nitric 
acid,  evaporate  to  dryness;  moisten  it  with  calcium  chloride, 
and  evaporate  to  dryness  again.  If  inosite  is  present,  a  rosy 
red  spot  will  remain. 

If  crystals  have  been  formed,  dissolve  some  in  water,  in  which 
they  are  easily  soluble,  and  apply  the  same  test. 

68.  Brain. — The  brain  contains  cholesterin,  lecithin,  and 
cerebrin,  besides  albuminous  substances,  which  chiefly  form  the 
axis  cylinders,  and  are  insoluble  in  water.  Cerebrin  probably 
belongs  to  the  white  substance  of  nerves. 

The  specific  gravity  of  the  brain  may  be  ascertained  in  the 
manner  directed  in  A  pp.  §  210,  and  the  amount  of  water  it 
contains  by  weighing  it,  drying  it  in  a  hot  chamber,  or  over 
sulphuric  acid,  and  estimating  the  loss.  To  separate  the  sub- 
stances contained  in  the  brain,  remove  the  membranes  and  ves- 
sels as  much  as  possible  from  it,  wash  its  surface  with  water, 
and  rub  it  to  a  paste  in  a  mortar.  Mix  it  with  great  excess  of 
alcohol,  and  let  it  stand  for  several  days,  stirring  it  frequently. 
Separate  the  alcohol  by  filtration,  and  set  it  aside  for  the  pre- 
paration of  lecithin.        .......         (a) 

Knit  up  the  brain  again,  and  extract  it  with  large  quantities 
Of  ether,  as  long  as  they  take  up  much  lecithin  or  cholesterin. 


456  CHEMISTRY    OF    THE    TISSUES. 

This  is  known  by  evaporating  a  small  quantity  of  the  ether 
each  time  it  is  taken  from  the  brain.  Put  the  ether  aside ;  ex- 
tract the  brain  with  hot  alcohol  several  times,  and  filter  it  hot. 
On  cooling,  cerebrin  will  crystallize  out,  mixed  with  lecithin. 

69.  Cerebrin. — Purification. — Filter  off  the  alcohol  from 
the  crystals,  wash  them  with  cold  ether,  and  boil  them  for  an 
hour  with  baryta  water.  Pass  C0.2  through  the  liquid  to  pre- 
cipitate the  excess  of  baryta  ;  filter,  and  wash  the  precipitate 
first  with  cold  water  and  then  with  cold  alcohol.  Put  the  pre- 
cipitate in  a  beaker  with  alcohol  and  heat  it,  to  extract  the 
cerebrin  from  it,  and  filter  it  hot.  On  cooling,  crystals  of 
cerebrin  will  be  deposited,  which  should  be  again  dissolved  in 
hot  alcohol,  allowed  to  crystallize  out  again,  washed  with  ether, 
and  dried  at  a  moderate  temperature. 

Cerebrin  forms  a  white  hygroscopic  powder.  Put  a  little  on 
a  piece  of  platinum  foil  and  heat  it.  It  will  become  brown, 
melt,  and  then  burn. 

From  the  mode  of  preparation,  it  is  evident  that  it  is  inso- 
luble in  cold  but  soluble  in  hot  alcohol,  and  that  it  is  not  de- 
stroyed by  boiling  with  baryta  water. 

Put  it  in  water.  It  will  slowly  swell  up,  somewhat  like 
starch. 

70.  Lecithin. — Add  to  the  alcoholic  extract  (a)  a  solution 
of  platinum  chloride,  acidified  with  hydrochloric  acid.  A  }'el- 
low  flocculent  precipitate  of  lecithin  platinum  chloride  will 
fall.  Filter,  and  dissolve  the  precipitate  in  ether ;  pass  hydro- 
gen sulphide  through  the  solution  to  precipitate  the  platinum. 
Filter  and  evaporate.  Lecithin  chloride  will  remain  a  waxy 
mass. 

Decomposition. — When  treated  with  acids  or  with  boiling 
baryta  water  it  is  decomposed,  and  yields  glycerophosphoric 
acid,  neurin,  and  fatty  acids. 

Dissolve  some  lecithin  chloride  in  alcohol  and  pour  it  into 
boiling  baryta  water.  It  will  be  decomposed,  and  a  smeary 
precipitate  will  fall. 

71.  Neurin. — Filter ;  pass  CO.,  through  the  filtrate  to  re- 
move the  baryta ;  filter ;  evaporate  to  dryness ;  extract  with 
alcohol.  Add  to  the  alcoholic  extract  platinum  chloride,  and 
a  precipitate  of  neurin  platinum  chloride  will  fall.  The  pla- 
tinum may  be  removed  by  hydrogen  sulphide  and  the  neurin 
chloride  obtained,  but  it  is  with  difficulty  crystallizable. 


BY   DR.    LAUDER   BRUNTON.  457 


CHAPTER  XXXVII. 

DIGESTION. 

Section  I. — Saliva  and  its  Secketions. 

72.  Mode  of  obtaining  Mixed  Saliva. — To  obtain  a 
sufficient  quantity  of  human  saliva  for  examination,  the  secre- 
tion of  the  salivary  glands  must  be  stimulated  artificially. 
For  this  purpose  anj7  of  the  mechanical  or  chemical  stimuli  to 
be  mentioned  in  §  85  may  be  used.  To  avoid  the  risk  of  the 
saliva  becoming  altered  by  mixture  with  the  substance  used 
to  quicken  its  secretion,  the  mechanical  stimuli  should  be  pre- 
ferred. There  is  no  objection,  however,  to  the  employment  of 
ether  vapor. 

**  73.  Examination  of  Mixed  Saliva — Appearance. — 
Saliva  is  transparent  or  opalescent.  It  sometimes  deposits  a 
white  precipitate  almost  immediately  after  it  has  been  col- 
lected. When  poured  from  one  vessel  to  another,  it  is  seen 
to  be  more  or  less  viscid,  in  consequence  of  which  it  is  gen- 
erally filled  with  air-bubbles.  If  none  are  present,  they  are 
readily  produced  by  blowing  into  the  liquid  through  a 
narrow  glass  tube,  when  it  is  seen  that  they  take  a  long  time 
to  subside.  If  the  saliva  is  allowed  to  stand  long,  a  thin  pelli- 
cle of  carbonate  of  lime  forms  on  its  surface.  Microscopical 
Examination. — Saliva  contains  numerous  air-bubbles,  paAre- 
ment  epithelium  cells  from  the  mouth,  and  round  cells  (sali- 
vary corpuscles)  resembling  tyrnph  corpuscles,  within  which 
are  numerous  granules  in  constant  movement. 

**  74.  Determination  of  the  Amount  of  Water  and 
of  Solids. — Take  a  small  porcelain  crucible  with  a  lid,  dry  it 
in  an  air-bath  at  100°  C,  put  it  under  a  bell-jar  over  a  dish 
containing  strong  sulphuric  acid  till  it  is  quite  cool,  then 
weigh  it  immediately  and  note  its  weight  carefully.  After 
weighing  it,  replace  it  in  the  air-bath  for  another  hour,  cool  it 
and  weigh  it  again  as  before.  If  the  weight  is  less  the  second 
time  than  the  first,  the  process  must  be  repeated  till  no  further 
loss  of  weight  occurs.  Introduce  some  saliva  into  it  and 
Weigh  again.  The  amount  of  saliva  used  is  ascertained  by  de- 
ducting the  weight  of  the  crucible  alone  from  the  weight  of 
the  crucible  and  its  contents,  thus : — 


458  DIGESTION. 

Wright  of  crucible  and  saliva     33.562  grm. 
Weight  of  crucible  alone  23.296  grin. 

10.2GG  =  weight  of  saliva  used. 

Evaporate  the  saliva  to  dryness  either  in  the  air-bath  or  over 
a  water-bath,  but  finish  the  desiccation  in  the  air-bath.  Cool 
and  weigh  the  crucible  as  before.  The  amount  of  solid  residue 
is  determined  in  the  same  way  as  that  of  the  saliva  itself, 
thus : — 

Weight  of  crucible  and  dried  residue     23.342  grm. 
"Weight  of  crucible  alone  23.200  grin. 

Difference  .046  grm.  =  weight 

of  residue. 

The  amount  of  water  is  found  by  subtracting  the  weight  of 
the  solid  residue  from  that  of  the  saliva  used,  thus  : — 

Weight  of  saliva  used         10.266 

"Weight  of  solid  residue  .046 

10.220  weight  of  water. 

10.220  x  100       nft  .       , 
Hence  percentage  of  water  =  •—        =  yy.O  and 

7>  -,.-,.,  0.046  x  100        n  .. 

Percentage  of  solid  residue  =  — . =0.44 

10.266 

*  75.  Qualitative  Investigation  of  Inorganic  Con- 
stituents.— For  this  purpose  the  saliva  must  be  filtered  so 
as  to  separate  the  epithelium  and  mucus.  It  contains  carbo- 
nates, chlorides,  phosphates  and  sulphates  of  potassium, 
sodium,  calcium,  and  magnesium,  and  in  most  cases  also 
potassium  sulphocyanide.  The  presence  of  these  several  salts 
may  be  demonstrated  as  follows  :  Carbonates. — If  a  drop  of 
saliva  is  placed  on  an  object-glass  and  covered  in  the  usual 
way,  and  a  drop  of  acetic  acid  added,  bubbles  of  gas  will  be 
seen  to  form  under  the  cover-glass.  Chlorides. — The  saliva 
is  acidulated  strongly  with  nitric  acid,  after  which  solution  of 
silver  nitrate  is  added  ;  the  precipitate  formed  is  insoluble  in 
excess  of  acid,  but  dissolves  readily  in  ammonia.  Sulphates. 
— The  turbidity  produced  b}r  solution  of  barium,  chloride,  or 
nitrate  does  not  disappear  when  nitric  acid  is  added,  and  the 
liquid  is  boiled.  Potassium. — If  a  little  saliva  is  gently  evapo- 
rated on  a  platinum  wire  and  then  heated  in  the  flame  of  a 
Bunsen's  lamp,  the  flame  seen  through  blue  glass  exhibits  a 
violet  color.  Sodium. — Without  the  glass  it  presents  the  well- 
known  yellow  color  due  to  the  presence  of  sodium.  Calcium 
may  be  precipitated  as  oxalate  by  the  addition  of  ammonium 
oxalate.  Magnesium  as  ainmoniaco-magnesian  phosphate.  To 
obtain  the  latter,  ammonium  chloride,  and  ammonia  must  first 


BY    DR.   LAUDER   BRUNTON.  459 

be  added,  then  sodium  phosphate.  Potassium  Sulphocyanide. 
— This  is  generally,  though  not  invariably,  present  in  mixed 
saliva.  It  is  derived  from  the  saliva  secreted  b}^  the  parotid 
gland,  and  is  not  contained  in  that  of  the  submaxillary  gland. 
To  show  its  presence,  add  a  drop  of  solution  of  perchloride  of 
iron,  so  very  dilute  as  to  be  almost  colorless,  to  a  little  saliva, 
in  a  porcelain  crucible  or  capsule,  and  stir  it.  A  reddish  color 
is  developed,  which  remains  unchanged  after  the  addition  of 
hydrochloric  acid,  but  is  at  once  removed  by  a  solution  of  cor- 
rosive sublimate.  Perchloride  of  iron  gives  a  similar  color 
with  acetic  acid  and  with  meconic  acid,  but  the  color  produced 
in  the  former  case  is  destnryed  by  h3'drochloric  acid  and  in 
the  latter  by  mercuric  chloride.  When  undiluted  perchloride 
of  iron  is  used,  the  color  is  deep  red,  and  ma}'  be  shown  to 
persons  at  a  little  distance.  If  the  test  does  not  at  first  suc- 
ceed, the  saliva  should  be  evaporated  to  one-third  of  its  bulk, 
and  the  test  then  applied. 

To  determine  the  percentage  of  inorganic  salts,  the  dry  resi- 
due must  be  incinerated  (see  §  214),  weighed,  and  calculated, 
as  in  §  74. 

*  76.  Organic  Constituents. — These  are  albumin, mucin, 
ptyalin.  Albumin. — If  saliva  is  strongl}'  acidified  with  nitric 
acid,  it  becomes  turbid,  but  no  precipitate  is  formed.  On  then 
boiling  it  becomes  clearer,  and  the  color  changes  to  yellow  ; 
the  addition  of  ammonia  changes  the  yellow  to  orange-red. 
If  to  another  portion  a  mixture  of  acetic  acid  and  potassium 
ferrocyanide  is  added,  a  white  precipitate  is  produced.  Saliva 
contains  two  albuminous  bodies — albumin  proper  dissolved  in 
salts,  and  globulin.  Globulin  is  precipitated  from  dilute  solu- 
tions by  CO,,,  ordinary  albumin  is  not.  To  separate  them,  a 
stream  of  carbonic  acid  gas  must  be  passed  through  saliva,  di- 
luted with  a  large  quantity  of  water,  for  some  time.  A  very 
fine  flocculent  precipitate  is  formed,  which  tends  to  disappear 
when  the  turbid  liquid  is  agitated  with  air.  After  the  precipi- 
tate has  settled,  the  liquid  may  be  decanted  off  with  a  syphon, 
and,  if  needful,  filtered  ;  it  can  then  be  proved  to  contain  albu- 
min by  the  addition  of  acetic  acid  and  ferrocyanide  of  potas- 
sium. This  process  requires  considerable  care.  Mucin. — To 
this  body  is  due  the  stickiness  and  tenacity  of  saliva.  If  acetic 
acid  is  gradually  added  to  saliva  while  it  is  stirred  with  a 
glass  rod,  it  becomes  more  and  more  tenacious,  and  finally  the 
mucin  separates  in  white  stringy  flakes  ;  these  must  be  washed 
with  water  and  acetic  acid,  and  tested  by  the  reactions  given 
in  §  45. 

**  77.  Action  of  Saliva  on  Starch  Paste. — Saliva  con- 
verts starch  into  sugar.  To  show  this,  prepare  some  thin 
mucilage  by  rubbing  up  a  little  starch  with  cold  water  into  a 
smooth  paste  and  pouring  a  large  quantity  of  boiling  water 


460  DIGESTION. 

over  it  (one  grain  of  starch  to  one  hundred  centimetres  of 
water),  or  by  boiling  it  in  a  flask  or  large  test-tube,  and  then 
allowing  it  to  cool.  Filter  the  saliva  to  be  used,  and  distribute 
it  in  three  test-tubes,  introducing  into  the  first,  starch  mucilage 
alone — into  the  second,  saliva — and  into  the  third,  saliva  with 
about  three  times  its  bulk  of  starch  paste.  Mix  them  well 
together  by  agitation.  Then  put  all  three  for  a  few  minutes 
into  a  water-bath  at  40°  C,  or  warm  them  gently  over  a  spirit- 
lamp.  Add  to  each  of  them  liquor  potassee  in  excess,  and  a 
drop  or  two  of  solution  of  cupric  sulphate.  In  the  first  and 
second,  a  light  blue  precipitate  will  be  thrown  down,  and  the 
liquid  will  remain  colorless ;  but  in  the  third,  the  precipitate 
just  formed  will  be  redissolved,  and  give  a  blue  solution.  If 
now  the  liquids  are  boiled,  the  precipitate  in  the  first  tube, 
containing  starch  paste,  alone  will  be  blackened,  but  the  liquid 
will  remain  colorless.  In  the  second,  containing  saliva,  the 
precipitate  will  be  partly  dissolved,  and  give  to  the  fluid  a 
violet  color,  due  to  albumin  in  the  saliva,  §  12.  In  the  third, 
a  yellow  or  orange  precipitate  will  be  formed.  This  reaction, 
which  is  known  as  Trommer's  test,  shows  that  there  is  no 
sugar  either  in  the  saliva  or  starch  used,  but  that  it  is  formed 
by  the  action  of  the  one  on  the  other.  Rapidity  of  concertina 
of  starch  into  sugar. — Bidder  and  Schmidt  erroneousl}-  con- 
sidered that  the  conversion  of  starch  into  sugar  was  almost 
instantaneous.  To  illustrate  this  view,  introduce  saliva  into  a 
small  beaker.  Place  it  in  a  water-bath  at  40°  C,  and  when  it 
is  warmed  through,  let  a  little  dilute  starch  mucilage,  colored 
with  iodine,  fall  into  it  drop  by  drop.  As  each  drop  falls  it 
becomes  decolorized.  The  disappearance  of  the  blue  color  is 
not  dependent  on  the  conversion  of  starch  into  sugar,  but  on 
the  conversion  of  the  iodine  into  hydriodic  acid.  Other  or- 
ganic fluids,  such  as  the  urine  of  dogs,  according  to  Schiff,  ex- 
hibit the  same  reaction,  which  is  probably  due  to  their  con- 
taining deoxidizing  substances,  for  the  same  effect  is  produced 
by  sulphurous  acid  or  morphia,  both  of  which  absorb  oxygen 
readily.  This  ma}r  be  shown  by  putting  starch  mucilage 
colored  with  a  little  iodine  into  a  test-tube  and  diluting  it  till 
it  forms  a  clear  blue  transparent  solution.  If  it  is  now  placed 
in  the  warm  bath  at  40°  C.,  it  will  remain  unaltered,  but  will 
at  once  lose  its  color  on  the  addition  of  either  of  the  reducing 
agents  above  mentioned. 

*  78.  Effect  of  Temperature  on  the  Diastatic  Action 
of  Saliva. — Take  four  test-tubes,  and  carefully  introduce  a 
little  saliva  into  each  with  a  pipette.  Put  the  first  into  a  mix- 
ture of  snow  or  ice  and  salt,  the  second  into  a  test-tube  rack 
on  the  table,  the  third  into  a  water-bath  at  40°  C. ;  boil  the 
fourth  briskly  for  two  or  three  minutes,  and  then  allow  it  to 
cool.     Theii  add  starch  paste  to  each  of  them,  and  allow  them 


BY   DR.    LAUDER   BRUXTOX.  461 

lo  remain  where  they  are  for  five  or  ten  minutes.  Take  a  part 
of  the  fluid  from  each,  and  test  it  for  sugar,  either  by  Trom- 
mer's  or  Moore's  tests.  (See  §  155.)  Xone  will  be  found  in 
the  first  or  fourth,  a  little  in  the  second,  and  more  in  the  third. 
Thus  we  learn  that  saliva  does  not  act,  or  acts  very  slowly,  at 
the  freezing  point,  that  it  acts  at  the  temperature  of  the  air,  and 
still  more  quickly  at  the  temperature  of  the  body.  Now  place 
the  first  and  fourth  test-tubes  in  the  water-bath  at  40  C,  allow 
them  to  remain  for  several  minutes,  and  test  again  for  sugar. 
It  will  be  found  in  the  first  but  not  in  the  fourth.  This  shows 
that  the  power  of  saliva  to  transform  starch  into  sugar,  is 
merely  suspended  by  exposure  to  a  very  low  temperature,  but 
is  totally  destroyed  b}-  boiling. 

*  79.  Influence  of  Acids  and  Alkalies  on  the  Dias- 
tatic  Action  of  Saliva. — Dilute  acids  do  not  arrest  the 
action  of  saliva  upon  starch  ;  stronger  acids  do  so  for  a  time, 
but  when  they  are  neutralized  the  action  again  goes  on. 

Take  three  test-tubes,  and  put  into  each  equal  parts  of 
saliva  and  starch  paste.  Add  to  the  first  its  own  bulk  of 
water,  to  the  second  a  similar  proportion  of  distilled  water, 
containing  0.65  per  cent,  of  commercial  hydrochloric  acid,  and 
to  the  third  the  same  quantity  of  dilute  acid  of  10  per  cent., 
and  keep  them  for  five  minutes  at  40°  C.  Add  liquor  potassae 
to  the  first  and  second,  and  test  for  sugar.  It  will  be  found 
in  nearly  equal  quantity  in  both.  Take  part  of  the  fluid  in 
the  third  tube,  and  test  it  for  sugar.  Xone  will  be  found. 
Neutralize  the  remainder  with  .carbonate  of  potash,  carefully 
avoiding  excess,  and  replace  the  test-tube  in  the  water-bath 
for  a  little  while.  On  again  testing  it,  sugar  will  be  found  to 
be  present. — As  the  greater  part  of  the  starch  we  eat  is  uot 
transformed  into  sugar  in  the  mouth,  but  is  swallowed  un- 
changed, it  is  important  for  us  to  know  whether  the  trans- 
formation goes  on  in  the  stomach  or  whether  it  is  arrested  by 
the  acid  gastric  juice.  The  strength  of  the  dilute  acid  just 
employed  (0.2  of  real  hydrochloric  acid)  is  nearly  the  same 
as  that  of  the  gastric  juice,  and  the  experiment  shows  that  in 
the  healthy  stomach  the  conversion  of  starch  into  sugar  may 
go  on  rapidly.  In  some  pathological  conditions  the  acidity 
of  the  gastric  juice  is  abnormally  increased,  and  the  action  of 
the  saliva  may  be  suspended  so  long  as  the  food  remains  in 
the  stomach,  but  when  the  acid  is  neutralized  by  the  intestinal 
secretion,  the  action  will  go  on  again. 

Alkalies. — Caustic  potash  and  soda,  when  added  to  the 
saliva  in  excess,  put  a  stop  to  its  action  on  starch,  and  its 
diastatic  power  is  not  restored  by  neutralization.  Its  action 
is  suspended  by  sodium  and  potassium  carbonates,  ammonia 
and  lime-water,  but  restored  by  neutralization.  Put  saliva  in 
two  test-tubes  and  add  to  one  several  drops  of  liquor  potassie. 


4G2  DIGESTION. 

and  to  the  other  a  few  drops  of  a  solution  of  potassium  car- 
bonate, mix  a  little  starch  mucilage  with  both,  and  let  them 
stand  in  a  water-bath  at  40°  C.  for  half  an  hour.  Test  a  small 
portion  of  the  liquid  from  both  tubes,  and  having  ascertained 
that  neither  contains  sugar,  put  a  drop  of  litmus  solution  in 
each,  and  neutralize  with  dilute  hydrochloric  acid.  After  both 
have  stood  for  another  half  hour,  sugar  will  be  found  in  the 
one  to  which  the  carbonate  was  added,  but  not  in  the  other. 

*  80.  Action  of  Saliva  on  Raw  Starch. — As  has  been 
seen,  the  saliva  rapidly  converts  starch  mucilage  into  sugar, 
but  it  does  not  act  so  quickly  on  raw  starch.  The  starch 
granules  consist  of  a  number  of  layers  arranged  in  an  eccentric 
manner  round  a  point  called  the  hilum.  These  laj'ers  consist 
alternately  of  two  substances  which  have  been  termed  respec- 
tively, starch-cellulose  and  starch-gran ulose.  The  latter  is 
colored  blue  by  iodine  alone ;  the  former  is  not  colored  unless 
the  granules  have  been  previously  acted  on  by  sulphuric  acid 
or  zinc  chloride.  When  starch  is  digested  with  saliva,  the 
granulose  onty  is  dissolved,  and  although  the  starch  granules 
still  retain  their  form,  they  are  no  longer  colored  blue  by 
iodine. 

To  show  this,  potato  starch  must  be  mixed  with  saliva,  and 
subjected  for  two  or  three  days  to  a  temperature  of  35°  C. 
The  saliva  used  must  be  decanted  off,  and  a  fresh  quantity 
added  every  two  or  three  hours.  The  starch  is  prepared  for 
the  purpose  by  placing  a  quantity  of  the  pulp  obtained  by 
scraping  the  cut  surface  of  a  raw  potato  on  a  bit  of  calico 
stretched  over  the  mouth  of  a  beaker,  and  theu  washing  it 
with  a  gentle  stream  of  water.  The  starch  granules  pass 
through  into  the  beaker,  leaving  a  fibrous  residue  on  the 
calico. 

81.  Artificial  Saliva.— As  ptyalin  is  present,  ready 
formed,  in  the  salivary  glands,  a  fluid  which,  like  saliva,  will 
convert  starch  into  sugar,  can  be  obtained  by  making  an  infu- 
sion of  the  glands. 

Take  the  salivary  glands  of  an  ox,  sheep,  rabbit,  or  guinea- 
pig.  Remove  the  cellular  tissue  from  them,  chop  them  up  fine, 
and  let  them  stand  with  a  little  water  upon  them  for  several 
hours.  Strain  through  muslin  and  filter.  The  filtrate  may 
be  used  instead  of  saliva  for  the  experiments  already  described. 

*  82.  Preparation  of  Ptyalin  from  the  Salivary 
Glands. — Ptyalin  may  be  separated  from  the  infusion  of  the 
glands  in  the  same  manner  as  from  saliva,  but  as  it  dissolves 
very  readily  in  glycerin,  it  is  much  more  advantageous  to  ex- 
tract it  by  that  agent.  For  this  purpose  prepare  the  salivary 
glands  of  an  ox  or  sheep,  as  above  directed.  Place  the  well- 
minced  gland  in  a  flask,  and  cover  it  with  absolute  alcohol. 
Cork  the  mouth  of  the  flask,  and  let  it  stand  for  twenty-four 


BY    LR.   LAUDER   BRUNTON.  463 

hours.  Then,  having  poured  off  the  liquid,  squeeze  the  re- 
mainder in  a  cloth,  so  as  to  get  rid  of  as  much  of  the  alcoholic 
extract  as  possible.  The  cake  so  obtained  must  now  be  mixed 
with  as  much  glycerin  as  will  cover  it  in  a  beaker,  and  allowed 
to  remain  for  several  days,  during  which  the  mixture  may  be 
occasionally  stirred.  At  the  end  of  this  period,  the  whole 
must  be  strained  through  muslin,  and  then  filtered  through 
paper.  In  the  filtrate,  ptyalin  is  precipitated  by  the  addition 
of  alcohol  in  excess.  The  precipitate,  after  having  been  col- 
lected by  subsidence  and  decantation,  must  be  dried  over  sul- 
phuric acid. 

83.  Separation  of  Ptyalin  from  Saliva. — The  method 
emploj-ed  for  separating  ptyalin  as  well  as  other  ferments  from 
the  secretions  in  which  they  are  contained,  depends  on  the  fact 
that  when  a  copious  precipitate  is  produced  in  the  fluid,  the  fer- 
ment adheres  to  the  particles  of  the  precipitate,  and  is  carried 
down  along  with  them.  It  does  not,  however,  adhere  very 
closely  to  the  precipitate,  and  can  readily  be  washed  off.  The 
precipitate  employed  to  carry  down  ptj'alin  is  calcium  phos- 
phate. This  carries  down  with  it  not  onty  the  ptyalin,  but 
also  the  albumin  in  the  saliva.  The  albumin,  however,  adheres 
more  closel}T  than  the  ptyalin  to  the  precipitate,  so  that  the 
ptyalin  is  dissolved  away  by  the  first  wash -water,  while  the 
albumin  remains  adherent.  Collect  a  considerable  quantity  of 
saliva  by  filling  the  mouth  with  ether;  while  fresh,  acidify  it 
strongly  with  phosphoric  acid,  so  that  the  precipitate  to  be  pro- 
duced may  be  voluminous;  then  add  milk  of  lime  till  the  fluid 
has  a  faintly  alkaline  reaction,  and  filter.  When  the  fluid  has 
drained  from  the  precipitate,  remove  the  latter  into  a  fresh 
beaker,  add  to  it  a  little  water,  not  exceeding  in  amount  the 
saliva  originally  employed,  stir  it  well  and  filter  again.  Add 
to  the  filtrate  an  excess  of  alcohol.  After  some  time  a  fine 
white  flocculent  precipitate  will  separate,  which  must  be  col- 
lected in  a  filter  and  dried  over  sulphuric  acid.  It  then  forms 
a  snow-white  powder,  and  consists  of  pt3'alin  mixed  with  some 
inorganic  salts.  To  obtain  it  free  from  ash,  dissolve  it  in  water, 
and  precipitate  it  again  by  absolute  alcohol.  Pour  off  the  alco- 
hol, dissolve  again  in  water,  and  precipitate  again.  Repeat  this 
several  times,  collect  the  precipitate  on  a  filter,  wash  with  dilute 
alcohol,  and  then  with  a  little  water,  and  finally  dry  it  at  a  low 
temperature,  under  a  bell-jar  over  sulphuric  acid. 

*  84.  Properties  of  Ptyalin. — The  reactions  of  ptyalin 
may  be  examined  either  in  the  filtered  aqueous  solution  of  the 
calcium  phosphate  precipitate,  or  in  solutions  of  pure  ptyalin. 
Ptyalin  differs  entirely  from  albumin  in  its  reactions. 

1.  Add  nitric  acid;  there  is  no  precipitate.  Boil  the  liquid, 
allow  it  to  cool,  and  add  ammonia.   No  yellow  color  is  produced. 

2.  Add  to  several  portions  in  test-tubes,  mercuric  chloride; 


4G4  DIGESTION. 

tannic  acid  ;  acetic  acid  and  solution  of  potassium  ferrocyanide ; 
platinum  chloride;  solution  ofiodine.  No  precipitate  appears 
in  any  case,  but  the  iodine  produces  a  yellow  color. 

3.  Add  lead  acetate,  and  to  another  quantity  basic  lead  ace- 
tate. In  both  cases  a  precipitate  is  formed  after  a  time,  and  on 
filtration  it  is  found  that  the  filtrate  is  without  action  on  starch, 
the  ptyalin  having  been  carried  down  with  the  precipitate. 

4.  Add  liquor  potassaiand  cupric  sulphate.  No  reduction  of 
the  copper  oxide  occurs. 

**  85  Secretion  of  Saliva. — The  secretion  of  saliva  goes 
on  very  slowly  or  ceases  entirely  when  the  glands  are  not  under 
the  influence  of  some  stimulus.  The  stimulus  may  be  either 
mechanical,  chemical,  electrical,  or  mental.  The  student  may 
estimate  the  effect  of  different  stimuli  by  experiments  on  him- 
self, thus  :  Swallow  all  the  saliva  contained  in  the  mouth,  so  as 
to  empty  it  completely.  At  the  end  of  two  minutes  spit  out 
the  saliva  which  has  collected  in  the  mouth  into  a  small  beaker 
previously  counterpoised  (see  §  215)  and  weigh  it.  Again 
empty  the  mouth,  apply  the  stimulus  and  collect  the  saliva 
for  two  minutes  more,  and  weigh  as  before.  B}'  the  comparison 
of  the  two,  the  action  of  the  stimulus  may  be  judged  of.  The 
best  modes  of  stimulation  are  the  following: — 

1.  Mechanical Roll  a  pebble  or  glass  stopper  in  the  mouth, 

and  attempt  to  chew  it. 

2.  Chemical. — Touch  the  tongue  (1)  with  a  crystal  of  tartaric 
or  citric  acid,  or  (2)  of  sodium  carbonate;  (3),  fill  the  mouth 
with  ether  vapor,  allowing  it  to  pass  back  into  the  pharynx, 
and  retaining  it  for  some  time  in  the  mouth. 

3.  Electrical. — Touch  the  tongue  and  inside  of  the  cheeks 
with  the  electrodes  of  Du  Bois  Reymond's  induction  coil. 

The  effect  which  a  stimulus  applied  to  the  mouth  produces 
in  man,  on  the  secretion  from  the  parotid  and  submaxillary 
glands,  may  be  studied  with  greater  precision  by  means  of  a 
canula  or  syringe.  If  a  syringe  is  used,  its  nozzle  must  end  in 
a  funnel-shaped  dilatation.  This  is  applied  to  the  papilla  at 
the  orifice  of  Wharton's  or  Stenson's  ducts,  and  gentle  traction 
made  upon  the  piston.  A  stimulus  may  be  applied  to  the 
mouth,  and  the  rate  at  which  the  saliva  flows  afterwards  ob- 
served. It  is,  however,  more  satisfactoiy  to  use  a  canula,  which, 
with  a  little  practice,  can  be  introduced  into  the  ducts  with 
great  ease. 

*86.  Mode  of  Collecting  the  Secretions  of  the  Sali- 
vary Glands  unmixed  in  Man. — Insertion  of  a  Canula 
into  the  Submaxillary  Duct. — Draw  out  a  narrow  glass  tube  to 
a  fine  point,  and  at  the  place  where  it  seems  small  enough  to 
enter  the  orifice  of  the  duct,  notch  it  with  a  triangular  file, 
break  it  off,  round  the  edges  at  the  border  of  a  glass  flame  and 
allow  it  to  cool.     To  insert  a  canula  thus  prepared  into  his  own 


BY   DR.    LAUDER   BRUNTON.  465 

submaxillar}'  duct,  the  student  must  now  place  himself  before  a 
mirror,  with  a  bright  light  directed  into  the  mouth.  Fill  the 
mouth  with  vapor  of  ether,  or  chew  a  piece  of  pyrethrum.  Turn 
the  end  of  the  tongue  back  against  the  palate.  At  the  root  of 
the  frsenum  linguae  a  papilla  with  a  little  black  dot  is  seen  at 
each  side  of  the  middle  line.  From  these  two  dots,  which  mark 
the  orifices  of  Wharton's  ducts,  the  saliva  will  be  seen  to  issue. 
Insert  the  end  of  the  canula  into  one  of  them,  and  hold  it 
steadily  in  its  place.  The  entrance  of  the  canula  is  attended 
with  an  unpleasant  sensation,  not  amounting  to  pain.  At  first 
the  canula  fills  pretty  rapidly,  but  as  the  effect  of  the  ether 
passes  off,  the  flow  soon  diminishes.  If  it  is  desired  to  collect 
the  secretion,  a  piece  of  India-rubber  tubing  must  be  attached 
vto  the  wider  end  of  the  canula  before  inserting  it. 

Insertion  of  a  Canula  into  the  Parotid  Duct. — As  it  is 
hardly  possible  to  insert  a  canula  into  one's  own  parotid  duct, 
a  second  person  must  be  employed,  who  should  sit  opposite  a 
good  light  and  chew  pyrethrum  root  as  before.  The  method 
is  as  follows:  Draw  one  angle  of  the  mouth  outwards  and 
forwards  so  as  to  stretch  the  cheek.  Opposite  the  second 
molar  tooth  of  the  upper  jaw  the  small  papilla  is  seen  which 
marks  the  orifice  of  Stenson's  duct.  Insert  the  canula  and 
hold  it  steadily  but  carefully  in  its  place,  then  a  third  person 
may  blow  into  the  mouth  some  vapor  of  ether,  or  introduce  a 
little  diluted  tincture  of  pyrethrum. 

By  these  methods  a  sufficient  quantity  of  secretion  can  be 
collected  for  the  investigation  of  the  leading  properties  of  the 
two  secretions.  Both  possess  the  property  of  determining  the 
transformation  of  starch  and  sugar. 

87.  Study  of  the  Secretions  of  the  Salivary  Glands 
in  Rabbits. — The  ducts  of  the  salivary  glands  in  rabbits 
are  too  small  to  allow  of  the  easy  introduction  of  a  canula, 
but  the  secretion  may  be  readily  studied  by  cutting  the  duct 
across.  The  saliva  escapes  from  the  cut  end  and  collects  in 
drops.  When  the  secretion  is  slight,  it  may  be  rendered  readily 
visible  by  putting  over  the  end  of  the  duct  a  piece  of  bibulous 
paper  reddened  with  litmus.  The  saliva  is  absorbed  by  the 
paper,  and  produces  a  blue  spot,  which  increases  in  size,  more 
or  less  rapidly,  according  to  the  rate  of  secretion. 

*  Parotid  Gland. — The  duct  runs  from  behind  forwards 
across  the  masseter  muscle  about  its  middle,  covered  by  fascia. 
It  lias  branches  of  the  facial  nerve  on  each  side  of  it,  and  is 
parallel  with  the  transverse  facial  artery.  At  the  anterior 
edge  of  the  masseter  it  takes  a  direction  towards  the  middle 
line,  in  order  to  enter  the  mouth. 

If  a  vertical  incision  is  made  in  a  line  with  the  cornea 
through  the  skin  and  fascia  of  the  cheek  down  to  the  masseter, 
30 


466  DIGESTION. 

the  facial  nerves  and  transverse  facial  artery  are  cut  across  as 
well  as  the  duct. 

As  soon  as  the  bleeding  has  ceased,  the  discharge  of  saliva 
from  the  cut  end  may  be  investigated  in  the  manner  directed 
in  §  90. 

88.  Investigation  of  the  Secretions  of  the  Salivary 
Glands  in  the  Dog.  Permanent  Salivary  Fistulae. — 
Permanent  fistulae  may  he  made  either  with  or  without  insert- 
ing a  canula  in  the  duct.  In  the  method  to  be  described,  that 
of  Sch iff,  no  canula  is  used.  Permanent  Submaxillary  Fis- 
tula.— The  animal  having  been  placed  on  the  table,  and  its 
head  secured  with  the  aid  of  Bernard's  holder,  it  is  put  under 
the  influence  of  chloroform.1  Shave  the  hair  from  the  under 
surface  of  the  lower  jaw.  Make  an  incision  akuig  the  inner 
border  of  the  ramus  of  the  lower  jaw,  extending  forwards 
from  the  anterior  margin  of  the  digastric  muscle,  and  dividing 
the  skin  and  platj-sma.  Secure  every  vein  that  presents  it- 
self with  two  ligatures,  and  divide  it  between  them.  Divide 
the  mylohyoid  muscle  cautiously.  Underneath  it  will  be  found 
the  submaxillary  and  sublingual  ducts,  which  run  side  by  side, 
the  submaxillary  being  somewhat  larger  and  nearer  the  ramus 
of  the  jaw.  Isolate  the  duct  and  divide  it  as  near  as  possible 
to  its  entrance  into  the  mouth.  Close  the  wound  with  sutures, 
leaving  the  end  of  the  duct  projecting.  To  prevent  its  retrac- 
tion, pass  a  suture  through  it.  When  the  wound  heals,  the 
end  of  the  duct  will  come  away,  leaving  a  fistulous  opening. 
Examine  it  daily,  and  if  it  has  a  tendency  to  close,  pass  a  fine 
probe  into  it  and  along  the  duct. 

Permanent  Sublingual  fistula. — This  is  made  in  the  same 
way  as  a  submaxillary  fistula,  and  the  same  animal  may  be 
used  for  both,  but  the  two  fistulae  should  be  on  opposite  sides 
of  the  head. 

89.  Parotid  Fistula. — The  animal  having  been  secured 
and  placed  under  chloroform  as  before,  the  hair  is  clipped  from 
the  cheek  between  the  orbit  and  the  angle  of  the  mouth.  On 
running  the  finger  along  the  lower  border  of  the  z3-gomatic 
arch  from  behind  forwards,  its  anterior  and  inferior  root  is 
felt  at  its  insertion  into  the  superior  maxilla,  forming  an  arch, 
of  which  the  convexity  is  directed  backwards.  At  the  end  of 
this  arch,  between  its  insertion  into  the  maxillary  bone  and 
the  alveolus  of  the  second  molar  tooth,  a  little  depression-is 

1  In  administering  chloroform  to  a  dog,  great  care  must  be  taken  that 
the  vapor  is  sufficiently  diluted  with  air,  and  that  the  sponge  does  not 
come  into  contact  with  the  muzzle.  The  breathing  must  be  carefully 
watched  during  the  period  of  administration,  and  if  it  fails  it  must  be 
continued  by  alternately  compressing  and  relaxing  the  thorax.  If  this 
does  not  succeed,  no  time  must  be  lost  in  opening  the  trachea  and  com- 
mencing artificial  respiration. 


BY    DR.    LAUDER   BRUNTON.  467 

felt.  Exactly  on  a  level  with  this  depression,  and  in  a  line 
with  the  insertion  of  the  zygomatic  arch,  make  an  incision 
through  the  skin,  cutting  obliquel}'  in  a  direction  from  the 
inner  canthus  of  the  eye  towards  the  angle  of  the  mouth.  On 
dividing  the  subcutaneous  cellular  tissue,  the  facial  vein  and 
artery,  a  nerve,  and  the  parotid  duct  will  be  found  all  together. 
The  duct  lies  most  deeply  and  runs  from  behind  forwards, 
while  the  artery,  with  its  accompanying  vein,  pass  from  above 
downwards.  It  is  of  a  pearly  white  color.  Isolate  it,  and 
divide  it  as  near  the  mouth  as  possible.  The  wound  must  be 
closed  round  the  duct,  and  the  duct  secured  in  it  by  a  suture, 
just  as  in  the  case  of  the  submaxillary  gland. 

*  90.  Effect  of  Stimuli  on  Secretion. — In  animals  with 
permanent  fistulse,  whether  parotid  or  submaxillary,  it  can  be 
demonstrated  that  these  glands  do  not  secrete  excepting  when 
secretion  is  excited  by  stimulants.  The  stimulation  ma}-  con- 
sist in  the  introduction  into  the  mouth  of  sapid  substances, 
such  as  vinegar  (which,  in  common  with  acid  substances  in 
general,  acts  most  on  the  parotid),  quinine,  or  coloc3rnth,  or 
of  ether,  or  in  electrical  excitation  of  the  tongue.  The  action 
of  mental  stimuli  may  be  also  shown,  as,  e.  g.,  by  placing  a  bone 
before  the  nose  of  a  fasting  dog  without  allowing  him  to  reach 
it.  From  SchifTs  experiments,  it  appears  that  this  kind  of 
stimulation  has  no  effect  on  either  the  parotid  or  submaxillary. 
The  mastication  of  a  bone  produces  an  abundant  secretion  from 
both  glands,  but  mastication  of  a  tasteless  substance,  as,  e.  g., 
a  piece  of  wood,  has  no  effect  on  the  parotid,  and  a  very  slight 
one  on  the  submaxillary.  For  rabbits  a  piece  of  hard  biscuit 
should  be  used  in  place  of  a  bone. 

Experimental  Investigation  op  the  Functions  of  the 
Submaxillary  Gland. 

91.  Owing  to  its  comparatively  exposed  position,  the  sub- 
maxillary gland  has  been  more  completely  studied  than  either 
of  the  other  two.  The  investigation  of  its  functions  has  yielded 
results  which  have  acquired  an  importance  far  beyond  that 
which  they  possess  as  bearing  on  the  secretion  of  saliva.  They 
form,  indeed,  the  basis  of  all  that  is  known  as  to  the  nature  of 
glandular  action,  and  of  the  influence  exercised  on  it  by  the 
nervous  system.  Before  proceeding  to  describe  the  methods 
employed,  it  will  be  necessary  to  give  a  short  account  of  its 
anatomical  relations,  and  particularly  of  the  bloodvessels  and 
nerves  which  are  distributed  to  it. 

Nerves. — The  gland  receives  nerve  fibres  from  three  sources, 
viz.,  from  the  facial,  from  the  submaxillary  ganglion,  and  from 
the  cervical  sympathetic.  The  branch  of  the  facial  (known  as 
the  chorda  tympani)  reaching  the  neighborhood  of  the  duct,  as 
part  of  the  trunk  of  the  lingual  nerve,  leaves  that  nerve  as  it 


468  DIGESTION. 

crosses  the  duct,  in  order  to  accompany  the  latter  to  the  gland 
(see  fig.  307).  In  the  angle  which  it  thus  forms  with  the  lin- 
gual lies  the  submaxillary  ganglion  or  ganglionic  plexus  above 
mentioned.  From  it  fibres  originate  which  reach  the  gland 
along  with  the  chorda.  The  sympathetic  fibres  are  derived 
from  the  superior  cervical  ganglion. 

Physiologically,  the  nerves  derived  from  the  submaxillary 
ganglion  cannot  be  distinguished  from  those  of  the  chorda. 
When  the  chorda  is  irritated,  the  arteries  of  the  gland  dilate, 
the  blood-stream  becoming  much  more  rapid  ;  consequently, 
the  veins  leading  from  the  organ  pulsate,  and  if  they  are  opened 
they  jet  like  an  artery.  At  the  same  time,  the  secretion  dis- 
charged from  the  duct  becomes  copious  and  watery.  When 
the  sympathetic  fibres  are  excited,  the  arteries  contract,  and 
the  circulation  in  the  gland  is  retarded,  and  if  the  veins  are 
opened,  they  discharge  "  black"  blood  in  a  slow  stream.  The 
secretion  becomes  scanty  and  tenacious. 

It  was  first  demonstrated  experimentally  by  Ludwig  that  the 
increased  secretion  produced  by  excitation  of  the  chorda  is 
immediately  dependent  on  increased  activity  of  the  function  of 
the  secreting  elements  of  the  gland,  and  not  on  changes  in  the 
bloodvessels;  in  other  words,  that  in  the  submaxillary  gland 
the  process  of  secretion  is  not  a  mere  filtration,  but  is  effected 
by  changes  which  go  on  within  the  gland  itself,  of  such  a  nature 
as  to  determine  a  current  from  the  circulating  blood  towards 
the  duct.  This  conclusion  was  based  by  Ludwig  on  the  ob- 
servation :  first,  that  if  the  duct  is  constricted,  secretion  con- 
tinues, notwithstanding  that  the  pressure  in  the  interior  of  the 
gland  is  greater  than  that  in  the  arteries ;  and,  secondly,  that 
secretion  continues  after  circulation  has  ceased,  e.  g.}  after  the 
head  has  been  severed  from  the  body. 

More  recent  observations  make  it  probable  that  by  the  chorda 
tympani  two  kinds  of  fibres  find  their  way  to  the  gland,  viz., 
fibres  by  which  secretion  is  influenced  directly,  and  others 
which  are  "  vaso-inhibitory,"  i.  e.,  diminish  arterial  tonus. 
Among  the  most  important  observations  bearing  on  this  ques- 
tion are  those  lately  published  by  Heidenhain,  who  has  found 
that  injection  of  atropiainto  the  arteries  or  veins  of  an  animal 
deprives  the  chorda  of  its  power  of  over-secretion,  without  in- 
terfering with  its  vaso-inhibitory  function  ;  and  the  earlier  ex- 
periments of  Gianuzzi,  made  under  Ludwig's  directions,  in 
which  a  similar  effect  was  produced  by  the  injection  of  solution 
of  quinine,  half  per  cent,  hydrochloric  acid,  or  five  per  cent, 
solution  of  sodium  carbonate  into  the  gland  itself. 

**  92.  Demonstration  of  the  Functions  of  the  Chorda 
Tympani  and  Sympathetic  Fibres  of  the  Submaxil- 
lary Gland  in  the  Dog. — The  animal  having  been  secured, 
as  directed  in  §  88,  and  placed  under  chloroform,  with  the 


BY   DR.    LAUDER   BRUNTON.  469 

usual  precautions,  the  hair  is  clipped  from  the  jaws  and  neck, 
and  the  skin  cleaned  with  a  wet  sponge.  This  having  been  ac- 
complished, proceed  according  to  the  following 

Directions. — 1.  Make  an  incision  along  the  inner  boi'der  of 
the  lower  jaw,  beginning  about  its  anterior  third,  a  little  in 
front  of  the  insertion  of  the  digastric  muscle,  and  extend  it 
backwards  to  the  transverse  process  of  the  atlas,  dividing  the 
skin  and  platysma  {see  figs.  308  and  310). — 2.  Expose  the 
jugular  vein  at  or  near  the  point  where  it  divides  into  two 
branches  (j'  and  j"),  and  lay  bare  those  branches  also.  One 
of  them  (j')  passes  upwards  behind  the  gland  ;  the  other 
(j")  passes  forwards  below  it,  and  then  subdivides  into  two 
branches.  The  gland  itself  has  two  veins.  One  of  them  (d' 
fig.  308)  issues  from  its  posterior  aspect  and  enters  the  vein 
j'.  The  other  (d)  comes  from  its  lower  side  and  enters  the 
vein  j".  Sometimes  one  vein  (d)  is  larger,  sometimes  the 
other  (d'). — 3.  Tie  both  branches  of  the  lower  division  of 
the  jugular  opposite  3"  (fig.  310).  Tie  the  upper  branch 
where  it  crosses  the  ramus  of  the  jaw,  and  remove  the  part 
between  the  ligatures. — 4.  Tie  the  other  division  (J')  on  the 
distal  side  of  the  place  where  it  receives  the  vein  (d'  fig.  308) 
from  the  gland. — 5.  Remove  the  cellular  tissue  from  the  surface 
of  the  digastric  muscle,  and  from  the  groove  between  it  and 
the  masseter.  Be  careful  not  to  injure  the  facial  artery,  and 
the  duct  of  the  gland  which  passes  forwards  and  inwards 
between  the  muscles. — 6.  Separate  the  digastric  muscle  by 
means  of  a  director  or  aneurism  needle  from  the  facial  artery. 
Tie  the  arterial  twig  which  supplies  the  muscle.  Separate  the 
muscle  from  its  attachment  to  the  jaw,  or  divide  it  about  its 
anterior  third,  cutting  it  through  very  carefully,  so  as  not  to 
injure  the  duct  and  nerves  which  lie  below  it. — 7.  Lay  hold  of 
the  lower  end  of  the  digastric  with  a  pair  of  artery  forceps, 
and  draw  it  backwards.  This  brings  into  view  a  triangular 
space,  whose  apex  is  directed  forwards,  and  whose  base  is 
formed  by  the  reflected  digastric.  Its  lower  margin  (the  dog 
being  supposed  to  be  in  the  upright  position,  as  in  the  figures) 
is  formed  by  the  genio-hyoid  muscle,  and  its  upper  one  bj'  the 
ramus  of  the  jaw  and  the  lower  edge  of  the  masseter.  The 
anterior  half  of  its  floor  is  formed  by  the  mylo-hyoid  muscle, 
on  which  some  nerves  ramify.  The  carotid  artery  enters  the 
triangle  at  its  lower  angle,  and  runs  along  its  base,  giving 
off  first  the  lingual  artery,  secondly  the  facial.  Just  as  the 
carotid  begins  to  pass  in  front  of  the  digastric,  it  is  crossed  by 
the  hypoglossal  nerve  P,  and  is  accompanied  by  filaments  of 
the  sympathetic  tt'.  At  the  upper  angle  of  the  triangle,  several 
structures  pass  from  it  to  the  hilus  of  the  gland  close  to  the 
margin  of  the  digastric.  These  are — 1,  the  duct;  2,  the  nerves  ; 
3,  the  principal  artery  of  the  gland.     The  artery  is  given  off 


470  DIGESTION. 

by  the  facial  at  the  upper  angle  of  the  triangle.  It  lies  beneatli 
the  nerves,  but  is  easily  reached  by  drawing  them  aside. — 8. 
Carefully  isolate  the  digastric  by  a  director  or  aneurism  needle 
from  all  the  structures  just  mentioned.  Divide  it  close  to  its 
insertion  into  the  temporal  bone. — 9.  Divide  the  mylo-hyoid 
muscle,  cutting  its  fibres  across  about  their  middle,  and  reflect 
the  upper  half,  taking  care  not  to  injure  the  mylo-hyoid  never 
■which  lies  upon  it,  and  tying  all  the  veins  which  come  into 
view  on  its  surface  with  a  double  ligature.  This  brings  into 
view  the  lingual  nerve  L,  which  issues  from  under  the  ramus 
of  the  jaw  just  opposite  the  groove  between  the  masseter  and 
digastric  muscles,  and  after  passing  across  the  floor  of  the 
triangle  towards  the  middle  line,  enters  the  mucous  membrane 
of  the  mouth — 10.  Draw  the  parts  a  little  towards  the  middle 
line  with  the  fingers,  and  follow  the  lingual  nerve  to  the 
ramus  of  the  jaw.  A  small  twig  T  will  then  be  seen,  which 
passes  off  from  its  posterior  aspect,  bends  down,  making  a  sort 
of  loop,  and  then  runs  backwards  to  the  gland  in  close  relation 
to  the  duct.  This  nerve  is  the  chorda  tympani.  In  the  angle 
between  .the  corda  and  the  lingual  lies  the  submaxillary  gan- 
glion.— 11.  Isolate  the  chorda  tympani,  pass  a  thread  under 
it,  and  tie  the  two  ends  together,  so  that  the  nerve  may  be 
raised  from  its  place  at  will. — 12.  Isolate  the  lingual  nerve 
close  to  its  entrance  into  the  mouth,  and  pass  a  thread  under 
it. — 13.  To  reach  the  sympathetic,  divide  the  hypoglossal  nerve 
P  just  where  it  crosses  the  carotid,  and  raise  up  its  central 
end.  Close  to  the  inside  of  the  carotid  lies  the  vagus,  and 
when  this  is  raised  the  sympathetic  is  seen  underneath  and 
inside  of  it.  The  sympathetic  separates  from  the  vagus  at 
this  point  and  goes  to  the  superior  cervical  ganglion  (see  fig. 
309).  From  the  ganglion,  fibres  accompany  the  carotid  and 
enter  the  gland,  some  along  with  the  chief  artery  (0),  and 
others  with  the  other  arteiy  P'.  The  ganglion  can  easily  be 
found  by  following  the  carotid  filaments  backwards. — 14.  Place 
a  canula  in  the  submaxillary  duct.  The  ducts  of  the  sub- 
maxillary and  sublingual  glands  pass  along  the  middle  of  the 
triangle  close  to  each  other.  The  submaxillar}'  duct  lies  nearer 
the  ramus  of  the  jaw,  and  is  larger  than 'the  sublingual  duct. 
Isolate  it  slightly  with  an  aneurism  needle.  Pass  under  it  a 
thread  for  the  purpose  of  tying  in  the  canula.  Place  under 
the  duct  a  smooth  splinter  of  wood  or  a  piece  of  card  half  an 
inch  long  by  one-eighth  of  an  inch  wide,  on  which  it  may  rest. 
Close  the  duct  as  near  the  mouth  as  possible  with  a  clip,  or 
tie  a  thread  round  it  so  as  to  obstruct  it.  Pvaise  the  chorda 
by  the  thread  which  has  been  passed  round  it,  irritate  it  by  a 
weak  interrupted  current;  the  purpose  of  this  is  to  distend 
the  duct  witli  secretion,  and  thus  render  the  introduction  of  a 
canula  much  easier.     Let  an  assistant  lay  hold  of  one  edge  of 


BY    DR.    LAUDER    BRUNTON.  471 

the  duct  with  a  pair  of  fine  forceps  while  the  operator  lays 
hold  of  the  other  just  over  the  splinter  of  wood  on  which  it 
rests;  open  the  duct  between  them  with  sharp-pointed  scissors. 
Insert  the  canula  into  the  duct  and  tie  it  in. — 15.  Put  a  liga- 
ture round  the  jugular  vein  half  an  inch  or  an  inch  below  its 
bifurcation,  so  as  to  be  able  readily  to  introduce  into  it  a 
canula  when  necessary. 

In  the  preceding  directions,  all  the  steps  of  the  operative 
procedure  required  for  the  complete  investigation  of  the  func- 
tions of  the  submaxillary  gland  during  life  are  detailed.  The 
method  may,  however,  be  modified,  according  as  it  is  intended 
to  limit  the  observation  to  the  influence  of  direct  or  reflex  ex- 
citation of  chorda  tympani  on  the  secretion  of  the  gland,  or  to 
extend  it  to  this  investigation  of  the  vascular  changes  and  to 
the  functions  of  the  vascular  nerves. 

93.  Direct  and  Reflex  Excitation  of  the  Chorda 
Tympani. — Proceed  as  above  directed,  omitting  13  and  15. 
2,  3,  and  4  may  also  be  omitted,  provided  that  all  such  veins 
as  are  necessarily  involved  in  the  succeeding  steps  are  doubly 
ligatured  and  divided  between  the  ligatures.  Reflex  Excitation. 
— Divide  the  lingual  nerve  close  to  its  entrance  into  the  mouth, 
and  excite  its  central  end  with  the  secondary  coil  at  a  con- 
siderable distance  from  the  primary.  The  secretion  of  saliva 
is  increased.  The  animal  must  previously  be  allowed  to  recover 
from  the  chloroform,  or  no  increase  will  be  observed.  The 
reflex  action  of  the  lingual  is  abolished  during  narcosis  by 
opium,  as  well  as  by  chloroform.  **  Direct  Excitation.  —Divide 
the  chorda  close  to  the  point  at  which  it  leaves  the  lingual,  and 
place  the  peripheral  cut  end  on  theexcitor  (fig.  225),  removing 
the  secondary  coil  to  a  considerable  distance  from  the  primary. 
On  opening  the  key,  saliva  is  discharged  from  the  canula  (to 
which  an  end  of  India-rubber  leading  into  a  test-tube  has  been 
fitted).  It  begins  to  flow  a  few  seconds  after  the  excitation, 
but  not  immediately.  By  repeating  the  excitation  at  regular 
short  intervals,  the  discharge  can  be  maintained,  and  a  con- 
siderable quantity  collected. 

**  94.  Demonstration  that  the  Pressure  produced 
by  Secretion  in  the  Duct  of  the  Submaxillary  Gland 
-when  it  is  Obstructed  is  greater  than  the  Arterial 
Pressure. — A  canula  having  been  placed  in  the  carotid  of  the 
opposite  side  of  the  body  and  connected  with  a  mercurial  ma- 
nometer, a  second  manometer  is  connected  with  the  canula  in 
the  duct  of  the  gland.  The  pressure  indicated  by  the  latter 
gradually  increases  until  it  attains  a  height  greater  than  that 
indicated  by  the  former.  In  this  experiment  it  is  desirable 
that  the  tube  of  the  manometer  connected  with  the  duct  should 
be  narrow.  Its  proximal  arm  should  be  connected  by  a  side 
opening  with  a  pressure  bottle  at  a  height  of  about  four  feet 


472  DIGESTION. 

from  the  table, the  arrangement  being  the  same  as  in  the  man- 
ometer of  the  kymograph.  In  this  way  a  mercurial  pressure 
of  about  50  mill,  of  mercury  is  produced  in  the  duct  before 
excitation  is  commenced.  On  exciting  the  chorda  tympanic  it 
rises,  as  above  stated,  to  double  that  height  or  more.  For  this 
experiment  the  same  preparations  are  required  as  for  the  pre- 
ceding, and  the  same  animal  may  be  used.  The  ineasureinent 
of  the  arterial  pressure  in  this  experiment  may  be  advanta- 
geously omitted.  The  pressure  in  the  particular  case  may  be 
assumed  to  be  equal  to  the  average. 

**  95.  Excitation  of  the  Vascular  Nerves. — If  the 
filaments  which  accompany  the  carotid  or  principal  artery  of 
the  gland  are  excited,  a  few  drops  of  secretion  may  be  dis- 
charged, but  the  quantity  is  so  small  that  unless  care  is  taken 
that  the  canula  and  duct  are  quite  full  before  the  key  is  opened, 
the  effect  will  be  scarcely  perceptible.  The  secretion  thus  ob- 
tained is  so  thick  and  viscid,  that  the  canula  is  apt  to  become 
ch'oked  b}r  it. 

**  96.  Demonstration  of  the  Influence  of  Excitation 
of  the  Chorda,  and  of  the  Vascular  Filaments  on  the 
Circulation  of  the  Submaxillary  Gland. — For  this  pur- 
pose it  is  necessary  to  insert  a  canula  into  the  jugular  vein, 
which  has  been  exposed  fortius  purpose  (see direction  15).  In 
doing  so.  great  care  must  be  taken  that  the  vein  is  not  twisted, 
and  that  the  canula  is  properly  inserted  so  as  to  allow  the  blood 
to  flow  freely  out  of  it  from  the  gland;  it  will  be  remembered 
that  all  the  tributaries  of  the  vein,  excepting  those  from  the 
gland,  have  been  previously  tied.  On  exciting  the  chorda,  the 
blood  flows  from  the  canula  more  rapidly,  and  acquires  a 
brighter  color.  The  opposite  effect  is  produced  by  exciting  the 
vascular  filaments. 

97.  Simultaneous  or  Alternate  Excitation  of  the 
Chorda  Tympani  and  Vascular  Filaments  of  the  Sub- 
maxillary Gland. — The  same  degree  of  excitation  of  the 
chorda  which  is  sufficient  to  induce  a  marked  increase  of  the 
secretion  of  the  gland,  is  without  effect  if  the  sympathetic  fila- 
ments are  excited  at  the  same  time.  Hence  it  is  concluded 
that  the  functions  of  the  two  sets  of  fibres  are  antagonistic  to 
each  other,  not  only  in  relation  to  the  circulation  of  the  gland, 
but  as  regards  their  direct  influence  on  secretion.  The  experi- 
mental proof  of  this  consists  in  first  exciting  the  chorda  with 
the  secondary  coil  at  such  a  distance  that  the  effect  produced 
is  only  just  appreciable,  and  then  repeating  the  excitation  while 
the  vascular  filaments  are  excited  at  the  same  time.  In  the 
latter  case,  the  effect  of  the  excitation  of  the  chorda  is  annulled. 
If  with  a  Pohl's  commutator  the  same  induced  currents  are 
directed  alternately  through  the  chorda  and  the  sympathetic 
filaments  at  short  intervals,  the  preventive  influence  of  excita- 


BY    DR.    LAUDER   BRUNTON.  473 

tion  of  the  latter  manifests  itself  in  the  same  way  as  if  the  ex- 
citation were  simultaneous.  Here,  as  before,  the  effect  must  be 
verified  by  comparative  experiments. 

98.  Simultaneous  Section  of  the  Chorda  Tympani 
and  Vascular  Nerves. — Paralytic  Secretion. — After  divi- 
sion of  both  nerves,  the  secretion  of  the  submaxillary  gland, 
which  in  the  normal  state  only  goes  on  when  the  gland  is 
directly  or  reflexly  excited,  becomes  constant  and  abundant. 
This  effect  does  not  occur  until  some  time  after  section,  and 
may  last  for  days  or  weeks.  A  similar  condition  of  the  gland 
is  produced  by  the  introduction  of  curare  into  the  blood,  which 
is  supplied  to  the  gland  by  its  arteries.  To  show  this,  proceed 
as  follows  :  Find  the  facial  artery  and  prepare  it.  Then  insert 
and  secure  a  canula,  to  which  an  end  of  India-rubber  tubing 
has  been  previously  fitted  in  the  usual  way.  Fill  the  canula 
with  saline  solution,  and  connect  it  with  the  nozzle  of  a  Pravaz's 
syringe  previously  chai'ged  with  one  per  cent,  solution  of  curare, 
taking  care  that  the  India-rubber  tube  is  firmly  tied  round  the 
nozzle.  Open  the  clip,  inject  five  divisions  (about  two  milligr. 
of  curare),  and  then  close  the  clip.  The  same  mode  of  injection 
may  be  used  for  the  introduction  of  solution  of  atropin,  if  it  is 
desired  to  repeat  the  experiments  of  Heidenhain  previously 
referred  to. 

99.  Function  of  the  Submaxillary  Ganglion. — 
Bernard  found  that  excitation  of  the  central  end  of  the  lingual, 
when  divided  near  the  mouth,  produces  effects  similar  to  those 
of  excitation  of  the  chorda,  i.  e .,  causes  the  submaxillary  gland 
to  secrete  even  when  the  trunk  of  the  lingual  and  chorda  has 
been  severed  at  a  point  nearer  the  brain  than  that  at  which  it 
is  in  relation  with  the  ganglion. 

From  this,  Bernard  concluded  that  the  submaxillary  ganglion 
acts  as  a  reflex  centre,  independently  of  the  central  nervous 
system.  More  recent  observations  render  it  probable  that 
Bernard's  result  derives  its  explanation  from  the  anatomical 
fact  that  a  filament  of  the  chorda  exists,  at  all  events  in  some 
animals,  which  accompanies  the  lingual  nerve  for  about  an 
inch  and  a  half  beyond  the  point  at  which  the  chorda  separates 
from  it.  The  effect  in  question  is  to  be  attributed  to  excitation 
of  this  filament,  which  runs  back  parallel  with  the  lingual  nerve 
to  the  submaxillary  plexus,  and  so  to  the  gland.  (On  this 
subject,  nee  Schiff,  Physiol,  de  la  J)igestion,  t.  I.,  p.  288,  and 
Haartman's  Thesis,  1846.      Helsingtbrs,  p.  37,  and  PI.  I.  142.) 

100.  Parotid  Glands. —  In  most  animals  the  parotid,  like 
the  submaxillary  gland,  does  not  secrete  unless  the  nerves 
which  regulate  its  secretion  are  stimulated,  but  in  the  sheep  it 
is  said  by  Eckhard  to  secrete  constantly.  Secretion  occurs 
when  sapid  substances  are  applied  to  the  posterior  part  of  the 
tongue,  and  still  more  when  they  are  chewed ;  but  the  mere 


474  DIGESTION. 

motion  of  the  jaws  in  chewing  a  tasteless  substance  does  not 
induce  secretion.  The  gland  receives  two  secreting  nerves, 
one  of  which  is  derived  from  the  facial,  and  the  other  from  the 
sympathetic.  The  branch  from  the  facial  is  the  lesser  superfi- 
cial petrosal  nerve,  which  leaves  the  facial  in  the  petrous  por- 
tion of  the  temporal  bone,  passes  to  the  otic  ganglion,  and 
thence  to  join  the  auriculo-temporal  branch  of  the  fifth,  in 
which  it  proceeds  to  the  gland.  These  facts  have  been  experi- 
mentally ascertained  by  observing,  first,  that  irritation  of  the 
roots  of  the  facial  within  the  cranium  determines  flow  of  saliva 
from  the  parotid  gland  ;  secondly,  that  excitation  of  the  fifth 
nerve  within  the  cranium  has  no  such  effect ;  and,  thirdly, 
that  after  section  of  the  facial  nerve  at  its  exit  from  the  stylo- 
mastoid foramen,  the  application  of  stimuli  to  the  mouth  de- 
termines secretion  from  the  parotid  as  before.  These  facts, 
taken  in  combination,  show  that  the  secreting  fibres  for  the 
parotid  are  given  off  by  the  facial  in  its  passage  through  the 
petrous  part  of  the  temporal  bone.  This  conclusion  receives 
direct  confirmation  from  an  experiment  of  Bernard,  who  found 
that  destruction  of  the  facial  nerve  in  the  temporal  bone  stops 
the  secretion  of  the  parotid. 

Of  the  three  nerves  given  off"  bjr  the  facial  in  its  passage 
through  the  temporal  bone,  viz.,  the  chorda  lympani,  the  greater 
superficial  petrosal  and  the  lesser,  the  last-mentioned  was 
proved  by  Bernard  by  exclusion  to  contain  the  secreting  fibres 
for  the  parotid,  for  he  showed  that  the  chorda  could  be  divided 
in  the  tympanum  without  affecting  the  parotid  secretion  ;  and 
as  regards  the  greater  superficial  petrosal,  it  was  known  ana- 
tomically that  it  did  not  go  to  the  parotid,  and  also  found  ex- 
perimentally that  excision  of  Meckel's  ganglion  had  no  effect 
on  that  gland.  Bernard's  conclusion  has  received  direct  con- 
firmation from  later  experiments,  which  have  shown,  first,  that 
the  secreting  function  of  the  parotid  gland  is  much  impaired 
by  the  extirpation  of  the  otic  ganglion,  and  entirely  annulled 
1>3'  section  of  the  auriculo-temporal  nerve.  After  division  of 
this  nerve,  Schiff  has  shown  that  discharge  of  saliva  cannot  be 
induced  by  the  application  of  stimuli  to  the  mouth,  and  that 
electrical  excitation  of  the  peripheral  end  excites  secretion  just 
in  the  same  way  as  excitation  of  the  chorda  tympani.1 

1  For  a  description  of  the  method  of  dividing  the  facial  at  its  exit  from 
the  stylomastoid  foramen,  see  Eckhard's  Beitr'age  zur  Anatomic  und 
Physiologic,  Bd.  III.  p.  49.  Section  of  the  facial  within  the  temporal 
bone  is  described  in  Bernard,  Lecons  sur  la  Physiol,  et  la  Pathol,  du 
Syst.  Nerv.,  II.  pp.  58  and  141.  As  regards  section  of  the  chorda  in 
the  tympanum,  excision  of  the  sphenopalatine  ganglion,  and  division 
of  the  lesser  superficial  petrosal  nerve,  see  Schiff,  Physiol,  de  la  Diges- 
tion, torn.  I.  p.  229.  Excision  of  the  otic  ganglion,  do.  p.  227.  For 
the  method  of  exciting  the  auriculo-temporal  nerve,  see  Nawrocki  Stud, 
d.  Physiol.  Inst,  zu  Breslau,  lit.  IV.  p.  185. 


BY    DR.    LAUDER    BRUNTON.  475 

**  101.    Secretion   of  Saliva   after  Decapitation. — 

Make  a  parotid  fistula  in  a  rabbit;  decapitate  it;  split  the 
head  in  the  middle  line  by  a  knife  and  hammer;  remove  the 
brain  from  that  half  of  the  head  on  which  the  fistula  has  been 
made,  apply  a  piece  of  filter-paper  colored  red  by  litmus  to  the 
orifice  of  the  duct,  and  irritate  the  roots  of  the  facial  as  they 
enter  the  internal  auditory  foramen,  either  electrically  or  by 
touching  the  nerve  with  a  drop  of  acid.  A  blue  spot  will  appear 
on  the  paper,  showing  that  saliva  has  been  secreted. 

Section  II. — Digestion  in  the  Stomach. 

102.  In  the  stomach  the  albuminous  constituents  of  the  food 
which  were  unaffected  by  the  saliva  are  dissolved  by  the  gas- 
tric juice,  and  to  a  great  extent  converted  into  peptones.  If 
they  were  merel}T  dissolved,  they  could  only  be  absorbed  in 
very  minute  quantities,  for  albumin  will  hardly  diffuse  through 
animal  membranes.  The  peptones  into  which  the  albuminous 
substances  are  converted,  on  the  contrary,  diffuse  very  readily, 
and  are  thus  easily  absorbed.  The  gelatinous  substances  in 
the  food  are  also  changed  somewhat  h}'  the  gastric  juice,  so 
that  after  the}'  have  been  acted  on  by  it  they  no  longer  gela- 
tinize. The  transformation  of  starch  into  sugar  by  the  saliva, 
which  was  begun  in  the  mouth,  also  goes  on  in  the  stomach, 
the  acidity  of  the  gastric  juice  being  too  slight  to  arrest  it. 

Unlike  saliva,  gastric  juice  cannot  be  readily  obtained  from 
man  or  animals,  at  any  rate  in  a  state  of  purity,  without  an 
operation.  It  is  therefore  necessary  to  establish  a  gastric 
fistula  in  a  dog  in  order  to  collect  a  sufficient  quantity  of  gas- 
tric juice  for  examination. 

**  103.  Establishment  of  a  Gastric  Fistula.— The 
object  of  making  a  gastric  fistula  is  twofold  :  1st,  to  obtain 
gastric  juice  for  examination  ;  and,  2d,  to  observe  the  process 
of  secretion  within  the  stomach  itself. 

The  method  adopted  by  Bassow  was  simply  to  make  an  in- 
cision in  the  abdominal  parietes,  to  sew  the  stomach  to  the 
edge  of  the  wound,  and  then  to  make  an-opening  in  the  stomach 
itself.  The  fistula  was  plugged  with  a  piece  of  sponge.  It 
was,  however,  very  liable  to  close,  and  was  too  small  to  allow 
the  interior  of  the  stomach  to  be  observed.  Blondlot  pre- 
vented the  wound  from  closing  by  placing  in  it  a  canula,  which 
was  closed  with  a  cork,  so  that  the  gastric  juice  and  products 
of  digestion  might  not  be  lost  during  the  intervals  between 
his  observations. 

This  method,  as  improved  by  Bernard,  is  the  one  usually 
employed.  Bernard's  canula  consists  of  two  tubes,  each  of 
which  lias  at  one  end  a  broad  flange.  One  tube  screws  into 
the  other,  so  that  the  distance  between  the  two  flanges  can  be 


470  DIGESTION. 

altered  at  will.  This-  is  effected  by  means  of  a  key  which  fits 
on  two  projecting  points  in  the  inner  tube,  and  turns  it  round, 
while  the  outer  one  is  held  fast  by  the  fingers.  The  advantage 
of  this  form  over  a  simple  tube  with  a  shield  at  each  end,  is 
that  the  cicatrix  of  the  wound  often  thickens  in  healing,  and 
if  the  tube  is  not  proportionately  lengthened  the  outer  plate 
presses  on  the  skin  and  causes  ulceration.  The  disadvantage 
of  Bernard's  canula  is,  that  it  is  too  small  to  allow  the  in- 
terior of  the  stomach  to  be  conveniently  observed,  and  also,  I 
think,  that  the  edge  of  the  wound  comes  into  contact  with  the 
screw  of  the  inner  tube,  and  not  with  a  smooth  surface. 

These  advantages  may  be  readily  obviated  by  increasing  the 
diameter  of  the  tube  and  the  width  of  the  flange,  and  adapting 
a  key  to  the  projecting  points  by  which  the  outer  tube  may  be 
placed  in  the  stomach  and  turned  round  as  necessary.  Such  a 
canula  is  represented  in  fig.  311. 

104.  Operation  for  Gastric  Fistula. — Give  the  dog  a 
hearty  meal,  so  as  to  distend  its  stomach  completely  and  make 
it  lie  close  against  the  intestinal  walls.1  Anaesthetize  the 
animal  by  chloroform,  taking  care  that  the  vapor  is  mixed 
with  a  sufficient  proportion  of  air.  Lay  it  on  its  back  on  the 
table,  shave  off  the  hair  from  the  epigastric  and  hypochondriac 
regions,  and  remove  the  hairs  carefully  by  a  sponge,  so  as  to 
prevent  the  risk  of  their  getting  into  the  peritoneal  cavity. 
Make  a  vertical  incision  about  an  inch  and  a  half  to  one  side 
of  the  linea  alba,  preferably  the  left,  and  parallel  to  it,  extend- 
ing downwards  from  the  lower  edge  of  the  costal  cartilages  to 
a  distance  somewhat  less  than  the  diameter  of  the  flange  of  the 
canula.  Divide  the  muscles  parallel  to  the  course  of  their 
fibres.  Tie  every  bleeding  point  before  opening  the  perito- 
neum, so  that  no  blood  shall  get  into  its  cavity.  Open  the 
peritoneum  on  a  director.  Lay  hold  of  the  stomach  with  a 
pair  of  artery  forceps  at  a  point  where  there  are  not  many  ves- 
sels, and  draw  it  forwards.  Pass  two  threads  with  a  curved 
needle  into  the  gastric  walls  at  a  distance  from  each  other 
about  equal  to  the  diameter  of  the  tube  of  the  canula,  and 
bring  them  out  again  at  a  similar  distance  from  the  points 
where  they  were  introduced.  Make  an  incision  into  the  gastric 
walls,  between  the  two  threads,  rather  shorter  than  the  diame- 
ter of  the  tube  of  the  canula.  Put  a  pair  of  forceps,  with  the 
blades  together,  into  the  incision,  and  then  dilate  it  by  sepa- 
rating the  blades  till  it  is  large  enough  to  allow  the  canula  to 
be  introduced.  Push  the  canula  into  the  stomach  up  to  its 
outer  plate.     Tie  the  stomach  to  it  by  the  threads,  and   then 

1  Holmgren  recommends  the  inflation  of  the  stomach  with  air,  by 
means  of  a  tube  passed  down  the  oesophagus,  as  preferable  to  distend- 
in?  it  with  food. 


BY    DR.    LAUDER   BRUNTON.  477 

pass  their  ends  through  the  edges  of  the  wound  in  the  abdo- 
minal wall  in  such  a  way  as  to  fasten  the  stomach  to  it,  and 
at  the  same  time  to  keep  the  cut  edges  in  apposition.  No 
other  suture  is  required.  Leave  the  canula  uncorked  for  at 
least  half  an  hour  after  the  operation  is  finished,  for  when  the 
dog  recovers  from  the  chloroform  it  will  vomit,  and  if  the  ca- 
nula be  corked,  the  fluid  contents  of  the  stomach  are  apt  to  be 
forced  past  the  side  of  the  canula  into  the  abdominal  cavity. 
Feed  the  dog  on  milk  for  one  or  two  days,  and  if  the  operation 
be  performed  in  winter,  keep  it  in  a  place  warmed  night  and 
day.  The  day  after  the  operation  the  edges  of  the  wound  will 
be  much  swollen,  but  the  swelling  will  subside  in  a  day  or  two. 
After  the  wound  has  begun  to  heal,  the  cicatrix  may  thicken, 
and  the  outer  plate  of  the  canula  begin  to  press  too  much  on 
the  skin,  so  that  it  ulcerates.  If  this  should  occur,  the  canula 
must  be  lengthened  by  screwing  the  two  flangs  further  apart. 
The  canula  may  be  closed  by  an  India-rubber  stopper,  or  by  a 
cork.  If  the  dog  tears  out  the  cork  with  his  teeth,  soak  it  in 
decoction  of  colocynth,  or  put  a  little  phosphoric  acid  on  its 
outer  end. 

In  order  to  collect  the  juice,  let  the  animal  fast  for  several 
hours,  so  that  its  stomach  may  be  quite  empty,  but  not  for 
more  than  a  da}-,  as  the  mucous  membrane  would  become 
covered  with  a  thick  coating  of  mucous.  Let  an  assistant  pat 
the  dog,  and  keep  him  quiet ;  withdraw  the  cork  from  the 
canula,  and  tickle  the  inside  of  the  stomach  with  a  feather  tied 
to  a  glass  rod.  Put  a  small  beaker  underneath,  so  that  the 
end  of  the  rod  rests  on  its  bottom  :  the  gastric  juice  will  flow 
into  it  down  the  sides  of  the  rod. 

**  105.  Examination  of  Gastric  Juice.— The  gastric 
juice  is  thin,  almost  colorless,  very  faintly  opalescent,  and  has 
a  faintly  acid  taste.  Its  specific  gravity  is  nearly  the  same  as 
that  of  water.  Its  reaction  is  strongly  acid;  blue  litmus  paper 
becoming  bright  red  when  dipped  into  it. 

Composition. — In  the  dog,  it  contains  three  per  cent,  of 
solids;  in  man,  only  one  per  cent.  About  two-thirds  of  this 
is  organic  matter,  consisting  of  pepsin  and  peptones  ;  and  one- 
third  of  inorganic  matter,  consisting  of  chlorides  of  potassium, 
sodium,  ammonium,  calcium,  and  phosphates  of  calcium,  mag- 
nesium, and  iron.  The  specific  gravity  and  amount  of  solids, 
organic  and  inorganic,  are  to  be  determined  in  the  same  way 
as  those  of  saliva. 

The  acidity  of  the  gastric  juice  is  really  due  to  free  acid, 
and  not  to  acid  salts.  To  show  this,  the  amount  of  bases  and 
of  acid  contained  in  it  must  be  determined.  When  this  is 
done,  it  is  found  that  the  quantity  of  acid  is  more  than  suffi- 
cient to  form  acid  salts  with  all  the  bases  present  which  are 
capable  of  forming  such  salts  ;  it  must,  therefore,  exist  partly 


478  DIGESTION. 

in  a  free  state.  For  the  details  of  this  process,  consult  Bidder 
and  Schmidt,  Verdauungssafte,  u.  Stoffweehsel,  1852,  p.  44;  or 
Hoppe-Seylei's  Handbuch  d.  Chemischen  Analyse,  third  edi- 
tion, p.  434. 

106.  Estimation  of  the  Acid  in  Gastric  Juice. — Fill 
a  burette  with  dilute  standard  solution  of  soda  (one  part  in 
ten),  letting-  the  standard  solution  flow  gently  into  it,  so  as  to 
avoid  air-bubbles,  till  it  is  filled  above  the  zero  mark.  Then 
place  it  in  the  stand,  and  take  care  that  it  is  perfectly  vertical. 
If  any  bubbles  of  air  arc  present  they  must  be  allowed  to 
break  or  be  removed  by  a  glass  rod.  Let  the  fluid  flow  out  by 
pressing  the  clip  till  its  level  corresponds  to  the  zero  mark  on 
the  burette.  Measure  out  10  cubic  centimetres  of  gastric  juice 
into  a  beaker,  and  add  a  little  litmus  solution  to  it  till  a  dis- 
tinct red  color  is  produced.  Place  the  beaker  containing  it 
under  the  burette,  and  let  the  alkaline  solution  flow  gradually 
into  it  at  first,  and  at  last  only  drop  by  drop,  stirring  all  the 
time  till  the  red  color  of  the  litmus  changes  to  a  violet.  Then 
note  exactly  the  level  at  which  the  surface  of  the  fluid  stands 
in  the  burette.  The  difference  between  this  level  and  the  zero 
mark  gives  the  number  of  cubic  centimetres  used.  Calculate 
the  amount  of  soda  contained  in  this  quantity.  One  hundred 
cubic  centimetres  of  the  original  soda  solution  contained  four 
grammes,  or  one-tenth  of  an  equivalent  of  soda.  One  hundred 
cubic  centimetres  of  the  diluted  solution,  therefore,  contains 
one-tenth  of  this  amount,  0.04  grammes,  or  one-tenth  of  an 
equivalent. 

Let  us  suppose  that  the  amount  of  soda  solution  actually 
used  to  neutralize  the  gastric  juice  is  21.6  cubic  centimetres. 
Then,  as  100  cubic  centimetres  contain  0.04  grammes  (  =  0.01 
equivalent),  this  quantity  will  contain  only  0.00G  grammes 
(  =  0.00216  equivalent).  The  quantity  of  gastric  juice  neutral- 
ized was  10  cubic  centimetres.  Had  we  used  100  cubic  centi- 
metres of  juice  instead  of  10,  we  should  have  required  ten 
times  as  much  soda  to  neutralize  it,  i.e.,  0.0216  equivalent. 
One  hundred  cubic  centimetres  of  the  juice,  therefore,  contains 
0.021  of  an  equivalent  of  acid,  supposing  that  the  acid  be 
monobasic.  If  the  acid  be  bibasic  or  tribasic,  an  equivalent 
of  soda  would  only  saturate  a  half  or  a  third  of  an  equivalent 
of  acid,  and  the  proportion  of  acid  would  be  0.015  or  0.00?. 

107.  To  Determine  the  Nature  of  the  Acid.— The 
gastric  juice  is  introduced  into  a  large  retort  connected  with 
a  Liebig's  condenser,  and  distilled  till  the  fluid  in  the  retort 
becomes  very  concentrated,  and  clouds  begin  to  form  in  it. 
To  remove  the  excess  of  water  from  the  distillate,  it  must  be 
neutralized  with  sodium  carbonate,  evaporated  to  dryness  over 
a  water-bath,  extracted  with  absolute  alcohol  and  filtered. 
The  filtrate  is  then  evaporated  to  dryness  on  a  water-bath,  and 


BY    DR.    LAUDER   BRUNTON.  479 

the  residue  dissolved  in  a  small  quantity  of  water.  A  little  of 
the  solution  is  now  put  in  a  test-tube,  and  a  few  drops  of  a 
neutral  solution  of  ferric  chloride  added.  If  acetic  acid  is 
present,  the  fluid  will  become  of  a  dark  red  color,  and  when 
boiled  will  deposit  a  3'ellow  precipitate.  A  solution  of  silver 
nitrate  ma}'  be  added  to  second  portion.  If  hydrochloric  acid 
is  present,  a  white  precipitate  will  fall,  and  will  not  be  dis- 
solved on  adding  nitric  acid,  but  will  be  dissolved  by  ammonia. 
To  the  remainder,  dilute  sulphuric  acid  is  added,  and  the 
mixture  allowed  to  stand  for  some  time.  If  butyric  acid  is 
present,  a  smell  like  rancid  butter  will  be  perceived.  The 
residue  of  the  gastric  juice,  which  remained  in  the  retort  after 
the  hydrochloric  and  other  acids  were  distilled  off',  is  poured 
into  a  large  test-tube  or  flask,  and  agitated  with  ether.  The 
ethereal  layer  is  then  decanted  off  and  evaporated  over  a  water- 
bath.  If  acetic  acid  be  present  in  the  gastric  juice,  it  will 
remain  as  an  acid  residue.  Crystals  of  zinc  lactate  (square 
prisms  with  one  or  two  oblique  surfaces  at  the  ends)  may  be 
obtained  on  allowing  the  residue  to  stand  after  the  addition  of 
zinc,  oxide,  and  water. 

108.  Action  of  Gastric  Juice. — The  power  of  gastric 
juice  to  dissolve  coagulated  albuminous  substances  is  best 
shown  by  using  fibrin  from  blood.  To  prepare  fibrin  the  blood 
is  to  be  stirred,  as  it  flows  from  the  vessel,  with  a  rough  stick 
or  piece  of  ragged  whalebone,  and  the  fibrin  collected  and 
washed  till  it  is  perfectly  white.  It  may  be  preserved  for  a 
considerable  time  under  glycerin,  from  which  it  must  be 
washed  before  it  is  used.  Put  a  small  piece  of  fibrin  into  a 
test-tube  along  with  gastric  juice,  and  place  the  tube  for  an 
hour  or  two  in  the  water-bath  at  35°  C.  The  fibrin  will  swell, 
become  somewhat  transparent,  and  then  dissolve,  forming  an 
opalescent  fluid,  which  is  not  precipitated  by  boiling,  and 
slight^,  or  not  at  all,  by  neutralization.  As  no  other  fluid 
except  gastric  juice  has  this  action  on  fibrin,  the  production 
of  all  these  effects  is  used  as  a  test  for  it,  and  is  called  the 
pepsin  test.  Pepsin  alone  will  not  produce  them,  however, 
unless  free  acid  be  present  as  it  is  in  gastric  juice.  In  this 
process,  boiled  fibrin  ma}'  also  be  used  as  recommended  by 
Kiihne. 

**  109.  Artificial  Gastric  Juice. — All  the  actions  of  gas- 
tric juice  can  be  more  conveniently  studied  with  an  artificial 
juice  than  with  the  natural  secretion,  as  the  former  can  be  ob- 
tained in  much  larger  quantities.  The  method  of  preparing  it 
is  as  follows  :  Open  the  stomach  of  a  newly-killed  pig  or  rabbit, 
or  the  fourth  stomach  of  a  calf,  remove  its  contents  and  wash 
it  thoroughly  with  a  gentle  stream  of  water  without  much  rub- 
bing. Lay  it  on  a  piece  of  board  with  its  mucous  surface  up- 
wards, fasten  it  down  with  a  few  pins,  and  then  with  the  back 


480  DIGESTION. 

of  a  knife  or  an  ivory  paper-cutter,  scrape  off  all  the  mucus  from 
the  surface.  Rub  it  up  in  a  mortar  with  clean  silicious  sand 
or  powdered  glass  and  water,  let  it  stand  some  time,  stirring 
it  from  time  to  time,  and  then  fdter  it.  The  filtrate  is  gastric 
juice  in  a  state  of  very  considerable  purity.  It  is  slightly  opa- 
lescent, and  contains  a  large  quantity  of  pepsin  and  but  little 
peptone.  When  acidulated  with  its  own  bulk  of  dilute  hydro- 
chloric acid  of  0.2  per  cent.,  it  digests  fibrin  with  great  rapidity. 
It  may  be  kept  in  a  bottle  for  a  long  time,  and  though  fungi 
grow  on  its  surface,  it  still  retains  its  digestive  powers. 

A  much  stronger  gastric  juice,  though  not  so  pure,  is  ob- 
tained by  scraping  the  mucus  from  the  stomach  as  in  the  first 
process,  or  by  dissecting  off  the  whole  mucous  membrane  from 
the  muscular  layer,  cutting  it  into  small  pieces,  then  rubbing 
it  up  with  dilute  hydrochloric  acid  of  0.1  per  cent,  and  filtering. 
The  gastric  juice  so  readil}'  prepared  by  this  method  is  very 
strong,  and  does  very  well  for  experiments  on  digestion,  al- 
though it  contains  a  good  deal  of  albumin  which  is  dissolved 
in  the  acid.  It  maj-  be  freed  in  a  great  measure  from  albumin 
b}'  putting  it  into  the  water-bath  at  35°  C,  for  several  hours, 
so  as  to  convert  the  albumin  into  peptones,  and  then  transfer- 
ring it  to  a  dialyzer,  and  changing  the  water  several  times. 
The  peptones  will  diffuse  out  into  the  water,  a  great  part  of 
the  pepsin  will  remain  in  the  dialyzer. 

**  110.  To  Prepare  Hydrochloric  Acid  containing 
0.2  per  cent,  of  real  HC1. — The  ordinary  strong  hydrochlo- 
ric acid  sp.  gr.  1.16  contains  31.8  per  cent,  by  weight  of  II CI. 
gas.  To  prepare  a  dilute  acid,  containing  0.2  per  cent,  of  real 
HCL,  measure  out  with  a  graduated  pipette  6.25  cubic  centi- 
metres of  such  acid  into  a  litre  flask  ;  fill  the  flask  up  to  the 
neck  with  distilled  water,  and  shake  so  as  to  mix  thoroughly. 

**  111.  To  Prepare  a  Solution  of  Pepsin  in  Glycerin. 
— The  solubility  of  digestive  ferments  in  glycerin  was  dis- 
covered by  Yon  Wittich  ;  and  by  its  means  they  may  be  ob- 
tained with  great  facility.  Cut  open  the  stomach  of  a  pig 
or  rabbit  (best  when  newly  killed),  and  wash  the  mucous 
membrane  as  directed  ;  cut  off  the  pyloric  part ;  stretch  the  re- 
mainder on  a  piece  of  board,  and  dissect  off  the  mucous  mem- 
brane from  the  muscular  layer.  Cut  up  the  mucous  membrane 
into  small  pieces  and  put  it  into  a  beaker,  with  sufficient  gly- 
cerin to  cover  it.  It  will  acquire  peptic  properties  in  a  few 
hours,  but  it  is  as  well  to  let  it  remain  for  several  days.  Then 
strain  off  the  glycerin  and  put  on  a  fresh  quantity.  This  may 
be  repeated  several  times,  and  each  time  the  glycerin  will  take 
up  a  fresh  quantity  of  pepsin. 

An  artificial  gastric  juice  may  be  readily  prepared  whenever 
it  is  wanted  by  adding  a  little  of  the  glycerin  extract  to  hydro- 
chloric acid  of  0.1  per  cent. 


BY    DR.    LAUDER    BRUNTON.  481 

**  112.  Preparation  of  Pure  Pepsin  from  Glycerin 
Solution. — Let  the  mucous  membrane,  prepared  and  cut  into 
pieces,  as  already  directed,  lie  for  24  hours  in  absolute  alcohol. 
Filter  off  the  alcohol ;  dry  the  pieces  of  mucous  membrane  with 
a  cloth  or  filtering  paper,  cover  them  with  glycerin,  and  let  them 
stand  for  several  days  or  weeks.  Filter  the  glycerin,  first 
through  linen  and  then  through  paper.  Add  a  large  excess  of 
absolute  alcohol  to  the  filtrate  and  a  flocculent  precipitate  will 
fall.  Filter  off  the  alcohol,  pour  IIC1.  of  2  per  cent,  over  the 
precipitate  on  the  filter,  and  it  will  dissolve.  Boil  a  little  of 
the  solution  with  strong  nitric  acid,  and  after  cooling,  add  am- 
monia. It  should  not  give  the  slightest  trace  of  the  xantho- 
protein  reaction.  Let  a  piece  of  fibrin,  either  boiled  or  un- 
boiled, remain  in  another  portion  of  the  solution  for  several 
hours,  at  40°  C,  and  it  will  be  digested.  Apply  the  other 
tests  mentioned  in  §  118.  Very  probably  no  precipitate  may 
be  occasioned  by  platinum  chloride. 

113.  Preparation  of  Pepsin  (Brucke's  Method). — The 
process  by  which  Briicke  separated  pepsin,  and  thus  for  the 
first  time  succeeded  in  isolating  any  of  the  digestive  ferments, 
depends  on  their  being  tarried  down  from  their  solutions  along 
with  precipitates  produced  in  them.  This  has  already  been 
mentioned  when  speaking  of  saliva,  from  which  Cohnheim 
separated  ptyalin  by  Brucke's  process.  Separate  the  mucous 
membrane  from  the  stomachs  of  two  pigs,  and  cut  it  up  into 
small  pieces,  as  directed  in  §  109.  Digest  it  at  40°  C.  with  a 
considerable  quantity  of  dilute  phosphoric  acid,  of  the  British 
Pharmacopoeia,  mixed  with  its  own  bulk  of  water  (it  thus  con- 
tains 5  per  cent,  of  acid).  If  necessary,  remove  the  acid,  and 
add  fresh  portions  till  the  whole  of  the  stomach  has  been  dis- 
solved, with  the  exception  of  a  slight  residue,  continuing  the 
process  till  the  liquid  which  passes  through  on  filtering  gives 
no  precipitate  with  potassium  ferrocyanide.  Filter  the  liquid, 
put  a  little  of  the  filtrate  aside  in  a  test-tube,  and  add  lime- 
water  to  the  remainder  till  it  turns  blue  litmus  paper  slightly 
violet.  Collect  the  precipitate  on  a  cloth  filter,  press  all  the 
fluid  out  of  it  with  the  aid  of  a  screw-press,  and  dissolve  it  while 
still  moist,  in  water,  with  the  addition  of  dilute  hydrochloric 
acid  (50  cubic  centimetres  of  commercial  acid  in  a  litre-  of 
water). 

Precipitate  the  solution  a  second  time  with  lime-water,  col- 
lect the  precipitate  on  a  cloth  filter,  press  out  the  liquid,  pour 
a  little  water  on  it  while  still  moist,  and  add  phosphoric  acid 
to  it  in  small  quantities  and  at  long  intervals.  The  pasty  tri- 
basic  phosphate  Ca((P04).,  is  thus  converted  into  sandy  bibasic 
phosphate  Ca  II  P04.  Filter  off  the  fluid;  it  contains  pepsin 
still  mixed  with  albuminous  substances.  Test  its  digestive 
power  by  adding  a  few  drops  of  it  to  0.1  per  cent,  hydrochloric 
31 


482  DIGESTION. 

acid,  and  digesting  fibrin  in  it.  It  will  be  found  still  to  give 
the  xanthroprotein  reaction,  though  not  quite  so  strongly  as 
the  original  solution.  Wash  the  precipitate  upon  the  filter 
several  times  with  distilled  water,  plug  the  funnel,  and  pour  on 
dilute  phosphoric  acid,  so  that  a  part  of  the  Ca  II  P04  is  dis- 
solved, Ca  II4(POJ.,,  being  formed.  After  several  hours  remove 
the  plug  and  let  the  fluid  run  off.  It  will  digest  fibrin,  and  lias 
a  still  weaker  xanthoprotein  reaction.  Wash  the  precipitate 
several  times  with  distilled  water,  plug  the  funnel  again,  pour 
on  fresh  phosphoric  acid,  and  repeat  this  several  times.  At 
last  a  fluid  is  obtained  which,  although  it  digests,  gives  scarcely 
any  xanthoprotein  reaction.  To  prepare  pure  pepsin  in  sub- 
stance, prepare  a  solution  with  phosphoric  acid  and  lime-water, 
as  directed  above.  After  precipitating  a  second  time  with  lime- 
water,  and  pressing  the  precipitate,  dissolve  it  in  dilute  hy- 
drochloric acid  and  filter  it  into  a  large  flask.  Prepare  a  cold 
saturated  solution  of  cholesterin  in  a  mixture  of  4  parts  of  alco- 
hol of  808  sp.  gr.  and  one  part  of  ether.  Put  a  long  funnel 
which  will  reach  to  the  bottom  of  the  flask  into  it,  and  pour  in 
the  cholesterin  solution  in  small  quantities.  It  will  separate 
and  form  a  thick  scum  on  the  surface  of  the  fluid.  After  it  has 
attained  the  thickness  of  about  an  inch,  take  out  the  funnel, 
close  the  mouth  of  the  flask  and  shake  it  well,  so  that  as  much 
pepsin  as  possible  may  stick  to  the  cholesterin.  Filter  and 
wash  the  precipitate,  first  with  water  acidulated  with  acetic 
acid,  and  then  with  pure  water.  Continue  the  washing  until 
the  wash-water  no  longer  has  an  acid  reaction,  nor  gives  a  pre- 
cipitate with  silver  nitrate.  Put  the  moist  cholesterin  into  a 
precipitate  glass,  and  shake  it  with  some  ether  which  has  been 
previously  agitated  with  water  to  free  it  from  alcohol.  The 
ether  will  dissolve  the  cholesterin,  and  the  adhering  water  will 
separate  and  form  a  turbid  layer  at  the  bottom  of  the  glass. 
Pour  off  the  ether  and  shake  the  watery  solution  with  new 
quantities  of  ether  several  times,  until  a  few  drops  of  the  ethe- 
real solution  no  longer  leaves  behind  crystals  of  cholesterin 
when  evaporated.  Then  let  the  glass  stand  open,  to  allow  the 
last  thin  layer  of  ether,  which  cannot  be  poured  off*,  to  evapo- 
rate. Filter;  a  small  quantity  of  a  slimy  substance  remains  in 
the  filter,  but  the  filtrate  is  clear.  It  is  a  concentrated  solution 
of  pepsin,  and  the  following  reactions  may  be  tried  with  it,  or 
with  the  solution  of  pepsin  obtained  directly  from  the  lime  pre- 
cipitate. 

*  114.  Reactions  of  Pepsin. — To  show  the  following  reac- 
tions the  solutions  referred  to  in  §§  112  or  113  may  be  employed. 
It  is  not  precipitated  bj- — 1,  concentrated  nitric  acid  ;  2,  tannic 
acid;  3,  iodine  ;  4,  mercuric  chloride.  It  is  precipitated  by — 1, 
platinum  chloride;  2,  lead  acetate,  both  neutral  and  basic. 

If  absolutely  pure,  it  gives  no  xanthoprotein  reaction.    When 


BY   DR.    LAUDER   BRUNTON.  483 

allowed  to  evaporate  over  sulphuric  acid,  it  leaves  a  grayish 
amorphous  body,  which  contains  nitrogen,  and  is  not  hygro- 
scopic. It  is  sparingly  soluble  in  water,  more  readily  in  dilute 
acids,  and  digests  fibrin. 

115.  Digestive  Action  of  Pepsin. — Neither  pepsin  alone 
nor  dilute  hydrochloric  acid  alone  will  digest  fibrin,  but  when 
mixed  together  they  do  so  readily.  Pepsin  alone  has  no  action 
on  fibrin  whatever ;  hydrochloric  acid  of  0.2  per  cent,  alone 
causes  it  to  swell  up,  but  does  not  dissolve  it  for  days,  or  even 
weeks,  at  ordinary  temperatures.  At  35°-38°  C,  it  dissolves 
fibrin  readily  in  from  twent3'-four  to  forty-eight  hours,  but  only 
converts  it  into  syntonin,  so  that  the  whole  of  the  albuminous 
matter  (with  the  exception  of  a  trace  which  Von  Wittich  says 
is  really  converted  into  peptone),  may  be  precipitated  by  neu- 
tralization. Pepsin  with  dilute  hydrochloric  acid  likewise 
causes  fibrin  to  swell  and  dissolves  it,  forming  at  first  an  opa- 
lescent solution  of  syntonin  which  can  be  almost  entirely  pre- 
cipitated by  neutralization,  a  little  peptone  only  remaining  in 
solution.  Its  action  does  not  stop  here,  for  it  very  quickly  con- 
verts the  syntonin  (parapeptone)  into  peptones  which  are  not 
precipitated  by  neutralization  nor  coagulated  by  boiling,  but 
are  precipitated  by  alcohol,  and  possess  all  the  characteristic 
reactions  of  albuminous  bodies. 

116.  Products  of  the  Digestion  of  Albuminous  Com- 
pounds.— During  digestion  several  substances  are  formed,  to 
which  the  names  of  parapeptone,  dyspeptone,  and  metapeptone 
have  been  given  by  Meissner. 

Parapeptone. — Briicke  considers  that  albuminous  bodies  are 
converted  into  syntonin,  and  that  the  syntonin  is  transformed 
entirely  into  peptones  during  digestion,  but  Meissner  thinks 
that  the  syntonin,  instead  of  undergoing  this  transformation, 
splits  up  iuto  peptones  and  parapeptones.  Parapeptones 
agree  with  syntonin  in  every  respect,  except  that  they  cannot 
be  converted  into  peptones  by  any  amount  of  digestion,  while 
syntonin  can  be  digested.  When  an  albuminous  body  is  sub- 
jected to  the  action  of  gastric  juice,  the  solution  first  obtained 
yields,  on  neutralization,  a  precipitate  of  syntonin,  which, 
when  again  treated  with  gastric  juice,  is  converted  into  pep- 
tones. After  digestion  has  gone  on  a  little  longer,  the  pre- 
cipitate consists,  according  to  Meissner,  partly  of  syntonin 
and  partly  of  parapeptones,  for  he  states  that  if  this  precipitate 
is  digested  with  fresh  gastric  juice,  a  less  proportion  of  it  than 
of  the  former  precipitate  is  converted  into  peptones,  and  that 
this  proportion  diminishes  more  and  more  as  digestion  goes 
on,  and  the  remaining  syntonin  is  split  up.  Briicke  and  others 
have  found,  however,  that  fibrin  can  be  completely  converted 
into  peptones;  consequently,  Meissner  is  not  correct  in  sup- 
posing that  syntonin  splits  up  into  peptones  and  parapeptones. 


484  DIGESTION. 

Sometimes,  however,  several  clays  are  required  to  convert  the 
whole  into  peptones. 

Dyspeptone. — The  dyspeptone  of  fibrin  is  a  part  of  the  syn- 
tonin  or  parapeptone,  which  becomes  insoluble  in  2  per  cent, 
hydrochloric  acid,  and  therefore  falls  as  a  fine  precipitate.  It 
also,  according  to  Meissner,  is  incapable  of  further  digestion, 
and  only  differs  from  parapeptone  in  being  insoluble  in  dilute 
alkalies  and  dilute  acids,  and  therefore  is  precipitated  sponta- 
neously from  gastric  juice  without  neutralization. 

The  dyspeptone  of  fibrin  still  requires  investigation.  The 
dyspeptone  of  casein  has  lately  been  examined  by  Hoppe- 
Seyler  and  Lubavin  ;  as  it  consists  partly,  at  least,  of  a  non- 
albuminous  substance,  they  consider  casein  to  be  composed, 
like  haemoglobin  and  vitellin,  of  an  albuminous,  combined  with 
a  non-albuminous,  body. 

Metapeptone  is  merel}-  an  intermediate  stage  between  syn- 
tonin  and  peptone. 

Peptones. — There  are  several  kinds  of  peptones,  but  they 
still  require  further  investigation.  Meissner  distinguishes 
three  sorts,  which  he  names  a,  b,  and  c  peptones ;  c  is  the 
final  product,  the  others  being  probably  only  preliminary 
stages  in  its  production  ;  a  is  precipitated  from  neutral  solu- 
tions by  concentrated  nitric  acid,  and  from  solutions  slightly 
acidulated  with  acetic  acid  by  potassium  ferrocyanide  ;  b  is 
not  precipitated  by  concentrated  nitric  acid,  but  is  precipitated 
by  acetic  acid  and  potassium  ferrocyanide;  c  is  not  precipitated 
by  either  of  these  reagents. 

**  117.  Demonstration  of  the  Digestive  Action  of 
Pepsin. — Take  three  test-tubes,  and  put  into  the  first,  water 
with  a  few  drops  of  glycerin  extract  of  pepsin  ;  into  the  second, 
0.1  per  cent,  hydrochloric  acid;  and  into  the  third,  the  same 
acid  with  a  few  drops  of  the  glycerin  extract.  Throw  into 
each  a  small  piece  of  fibrin,  taking  great  care  to  choose  pieces 
not  only  of  the  same  size,  but  of  the  same  texture,  as  hard 
pieces  are  much  more  slowly  acted  on  either  by  acid  or  by 
gastric  juice.  Label  each,  or  note  the  number  of  the  hole  in 
the  rack  in  which  each  is  placed,  and  put  them  all  in  the  water- 
bath  at  40°  C.  (fig.  331).  In  order  to  obtain  a  sufficient 
quantity  of  solution  of  peptones  for  testing,  is  is  desirable  at 
the  same  time  to  put  a  larger  quantity  of  fibrin  in  a  beaker 
with  dilute  acid,  and  when  it  has  swollen  up  and  become 
transparent,  add  some  gh'cerin  extract  to  it,  and  place  it  with 
the  rest.  Look  at  the  test-tubes  again  in  five  minutes  or  so, 
and  if  the  pepsin  extract  is  strong,,  the  bit  of  fibrin  in  the  gas- 
tric juice  will  be  partly  dissolved,  while  the  one  in  the  acid 
will  have  swollen  and  become  translucent,  still  retaining  its 
form,  while  that  in  pepsin  alone  will  be  unchanged.  Filter 
the  artificial  gastric  juice  from  the  residue  of  fibrin.     Put  a 


BY    DR.    LAUDER    BRUNTON.  485 

drop  of  litmus  in  the  nitrate  and  neutralize  it;  a  precipitate 
of  syntonin  or  parapeptone  will  fall.  Filter  the  liquid:  the 
neutral  filtrate  containing  peptones  will  not  be  precipitated  by 
boiling,  but  it  will  give  the  xanthoprotein  reaction  strongly, 
and  will  give  a  precipitate  with  tannin.1 

For  the  further  examination  of  the  products  of  digestion, 
filter  the  solution  in  the  beaker  from  any  undissolved  residue. 
Neutralize,  and  parapeptones  will  be  precipitated.  Let  the 
precipitate  settle,  and  then  filter :  the  filtrate  will  contain  pep- 
tones. Test  for  a  and  b  peptones.  If  they  are  present,  put 
the  beaker  back  in  the  bath  for  a  while,  and  then  test  for 
them  again.  If  they  are  no  longer  present,  apply  the  follow- 
ing tests :  — 

**  118.  Reactions  of  Peptones. — True  or  c  peptones 
possess  the  following  characteristics :  They  are  not  precipitated 
by  (I)  neutralization,  (2)  boiling  the  solution,  either  neutral 
or  acid,  (3)  nitric  acid  either  in  the  cold  or  on  boiling,  (4) 
hydrochloric  acid  in  the  cold,  (5)  acetic  acid  and  potassium 
ferrocyanide — (after  standing,  the  fluid  becomes  turbid  and 
gives  a  precipitate) — (6)  copper  sulphate  in  small  quantity 
(if  more  is  added  it  causes  turbidity,  which  partly  disappears 
on  adding  excess).  They  are  precipitated  by  (1)  tannic  acid, 
(2)  silver  nitrate,  (3)  mercuric  chloride,  (4)  platinum  chloride, 
(5)  lead  acetate,  both  neutral  and  basic.  (The  precipitate  is 
soluble  in  excess.) 

The  solution,  when  treated  with  caustic  potash  and  an 
extremely  minute  quantity  of  copper  sulphate,  or  a  drop  of 
diluted  Fehling's  solution,  gives  a  precipitate  which  dissolves 
on  shaking,  and  forms  a  red  solution.  If  more  copper  sul- 
phate is  then  added,  it  becomes  violet.  Peptones  thus  differ 
from  albumin,  which  gives  a  violet  at  once. 

**  119.  DifFusibility  of  Peptones. — Put  a  solution  of 
peptones  into  a  small  dialyzer,  and  let  it  diffuse  into  distilled 
water  for  an  hour  or  two.  Then  test  the  water  by  the  tests 
given  above,  and  peptones  will  be  found  to  be  present.  In 
this  they  differ  from  albumin,  which,  as  has  been  already  seen, 
hardly  diffuses  at  all. 

*  120.  Action  of  Gastric  Juice  on  Gelatin. — Pepsin, 
with  dilute  hydrochloric  acid,  deprives  gelatin  of  its  power  to 

1  For  showing  the  action  of  pepsin  to  a  class,  Griinhagen's  method 
maybe  employed.  A  piece  of  moist  fibrin  is  placed  in  0.2  per  cent. 
hydrochloric  acid  till  it  swells  to  a  stiff  jelly.  It  is  then,  laid  on  a  funnel, 
either  with  or  without  a  filter,  and  after  the  superfluous  acid  has  drained 
off,  a  few  drops  of  glycerin  solution  of  pepsin,  or  artificial  gastric  juice, 
are  added  to  it.  The  rapidity  with  which  the  fibrin  is  converted  into 
peptone  is  shown  by  the  number  of  drops  which  fall  from  the  funnel. 
By  using  two  similar  lilt"rs,  the  power  of  different  digestive  fluids  may 
he  compared,  and  the  effect  of  temperature  shown  by  using  Planta- 
mour's  funnel. 


486  DIGESTION. 

form  a  jelly  sooner  than  dilute  hydrochloric  acid  alone.  Soak 
gelatin  in  cold  water  till  it  swells  up  completely,  and  then  add 
sufficient  boiling  water  to  it  to  form  a  concentrated  solution. 
Put  some  of  it  into  two  test-tubes,  and  add  to  each  its  own 
bulk  of  0.2  per  cent,  hydrochloric  acid.  Put  into  one  test- 
tube  a  little  glycerine  solution  of  pepsin,  and  into  the  other 
the  same  amount  of  glycerin,  and  place  them  in  the  water- 
bath  at  40°  C.  Take  them  out  after  an  hour  or  so.  and  let 
them  cool.  If  both  gelatinize,  replace  them  for  a  while,  and 
then  cool  them  again,  repeating  the  experiment  if  necessary. 
In  this  way  the  gelatin  in  the  gastric  juice  will  be  found  to 
lose  its  power  of  gelatinizing  somewhat  sooner  than  the  other. 

*  121.  Effect  of  Temperature  on  Digestion. — A  low 
temperature  arrests  the  action  of  pepsin  temporarily,  but  does 
not  destroy  its  activity.  It  acts  more  and  more  rapidly  as  the 
temperature  increases,  until  it  attains  its  maximum  between 
30°  C.  and  50°  C.  Above  this  the  action  becomes  slower.  It 
is  completely  annulled  by  boiling.  The  activity  of  a  dilute 
solution  of  pepsin  is  destined  by  exposure  to  a  temperature 
of  70°  C.  for  two  minutes,  and  by  a  still  lower  temperature 
when  exposed  for  a  longer  time.  The  activity  of  a  concen- 
trated solution  is  not  so  readily  destroyed,  and  that  of  an 
undiluted  glycerin  solution  is  retained  after  being  exposed  to 
80°  C.  for  two  minutes. 

To  show  the  action  of  temperature,  take  four  tubes,  and  put 
into  each  equal  quantities  of  0.1  per  cent,  hydrochloric  acid, 
to  which  a  little  gtycerin  solution  of  pepsin  has  been  added. 
Put  one  in  pounded  ice,  the  second  in  a  test-tube  rack  on  the 
table,  the  third  in  the  water-bath  at  40°  C,  and  boil  the  fourth, 
and  then  put  it  also  in  the  water-bath.  Put  into  each  a  bit  of 
fibrin,  and  let  them  stand.  The  fibrin  in  the  third  tube  will 
dissolve  quickly,  that  in  the  second  much  more  slovvlj'-,  that  in 
the  first  and  fourth  not  at  all.  After  a  while — say  half  an 
hour — take  the  tube  out  of  the  ice  and  put  it  in  the  water- 
bath.  The  fibrin  will  then  dissolve  quickly,  showing  that  the 
activity  of  the  pepsin  has  been  only  suspended.  That  in  the 
fourth  will  not  dissolve  at  all,  showing  that  the  pepsin  has 
been  destro}*ed. 

*  122.  Strength  of  Acid  required  for  Digestion. — 
The  strength  of  acid  with  which  albuminous  bodies  are  most 
quickly  digested  by  pepsin  varies  with  the  nature  of  the  body, 
and  also  with  the  amount  of  pepsin  present.  Very  dilute 
solutions  of  pepsin  digest  best  with  veiy  dilute  acids,  while 
more  concentrated  pepsin  solutions  act  more  quickly  with  a 
somewhat  stronger  acid.  There  seems,  indeed,  to  be  a  definite 
relation  between  the  amount  of  pepsin  and  the  strength  of  the 
acid,  though  what  this  is  has  not  yet  been  determined.  The 
proper  strength  of  acid   for  any  albuminous   body   may  be 


BY    DR.    LAUDER    BRUNTON.  487 

ascertained  by  placing  a  number  of  test-glasses  in  pairs,  the 
first  pair  containing  very  dilute  acid,  and  each  succeeding  pair 
a  stronger  acid.  In  each  glass  is  placed  a  little  of  the  albu- 
minous substance,  and  to  one  of  each  pair  au  equal  quantity 
of  solution  of  pepsin  is  to  be  added.  They  are  then  allowed 
to  stand,  and  the  rapidity  with  which  digestion  goes  on  in  each 
is  noted.  The  glasses  with  acid  alone  are  required  for  the 
purpose  of  comparing  its  effects  with  those  of  the  pepsin  and 
acid  together. 

It  can  be  shown  as  follows  that  digestion  is  hindered  when 
the  acid  is  either  too  weak  or  too  strong:  Take  three  test- 
tubes,  and  put  into  the  first  10  cubic  centimetres  of  0.1  per 
cent,  hydrochloric  acid,  mixed  with  three  times  its  bulk  of 
water  ;  into  the  second  the  same  quantity  of  a  similar  acid 
undiluted;  and  into  the  third  9^  cubic  centimetres  of  this  acid, 
and  half  a  cubic  centimetre  of  commercial  hydrochloric  acid. 
Place  in  each  a  bit  of  fibrin,  and  put  them  all  in  the  water- 
bath  at  40°  C.  The  fibrin  in  the  second  one  will  be  quickly 
digested  ;  that  in  the  first  and  third  tube  much  more  slowly. 
The  reason  of  the  slow  digestion  in  the  third  tube  will  be  seen 
in  the  next  experiment. 

*  123.  Influence  of  the  Swelling  of  Fibrin  on  its 
Digestion. — If  fibrin  is  prevented  from  swelling  up  under  the 
action  of  gastric  juice,  either  by  mechanical  means,  such  as  a 
thread  tied  round  it,  or  by  chemical  agents,  such  as  salt  solu- 
tions or  too  strong  acids,  its  digestion  is  much  retarded.  Put 
about  10  cubic  centimetres  of  0.1  percent,  hydrochloric  acid  into 
four  test-tubes,  and  add  to  that  in  the  fourth  test-tube  half  a 
cubic  centimetre  of  commercial  hydrochloric  acid.  Take  four 
bits  of  fibrin  as  nearly  as  possible  of  equal  size.  Wind  a 
thread  firmly  round  one  of  them,  and  drop  it  into  the  third 
test-tube.  Put  another  piece  into  each  of  the  other  tubes. 
As  soon  as  that  in  the  second  tube  begins  to  swell,  add  a 
saturated  solution  of  sodium  chloride  to  it  till  it  shrivels  again. 
Then  add  to  the  fluid  in  each  tube  half  a  cubic  centimetre  of 
glycerin-pepsin,  and  let  them  stand.  The  fibrin  in  the  first 
tube,  which  merely  serves  for  comparison,  is  soon  digested, 
and  dissolves  from  without  inwards.  The  bit  in  the  second 
tube  does  not  swell  again,  but  dissolves  from  within  outwards; 
so  that  a  sort  of  shell  remains,  which,  on  shaking,  falls  to 
pieces.  That  in  the  third  tube,  which  has  been  tied  with  a 
thread,  behaves  in  the  same  way.  That  in  the  stronger  acid, 
in  the  fourth  tube,  swells  incompletely,  but  dissolves  from 
without  inwards,  like  the  first. 

**  124.  Pepsin  is  not  destroyed  during  Digestion. — 
Although  the  aigesti-oe power  of  pepsin  appeal's  to  be  indefinite, 
yet  a  limited  quantity  of  gastric  juice  will  not  dissolve  an  nn- 
1 1  in  ittd  quantity  of fibrin — Adda  little  glycerin-pepsin  and  a 


4S8  DIGESTION. 

quantity  of  fibrin  to  some  0.2  per  cent,  hydrochloric  acid  in  a 
test-tube,  and  place  it  in  the  water-bath  at  4o  0.  for  several 
hours.  If  all  the  fibrin  is  digested,  add  more,  and  repeat  the 
addition  until  at  last  it  remains  undissolved,  however  long  it 
may  be  digested. 

The  arrest  of  digestion  in  this  experiment  is  not  due  to  de- 
struction  of  the  pepsin '.,  but  to  the  accumulation  of  the  products 
of  digestion  in  the  liquid,  andto  the  want  of  acid.  Dilute  the 
mixture  with  water,  and  put  it  in  the  water-hath  again,  and  di- 
gestion will  go  on  for  a  while  and  then  stop.  Jf  again  diluted, 
it  will  go  on  again,  but  the  action  will  be  slow  from  the  dilu- 
tion of  the  acid.  If  more  aeid  be  added,  digestion  will  proeeed 
more  quickly,  and  by  adding  fresh  quantities  of  acid,  a  very 
large  quantity  of  fibrin  may  be  digested. 

The  same  thing  may  be  shown  by  putting  the  fibrin  and  di- 
gestive fluid  in  a  dialyzer  and  letting  the  peptones  diffuse  out. 
The  digestive  fluid  is  then  to  be  evaporated  to  its  original  bulk, 
and  acidulated,  when  it  will  digest  the  same  amount  of  fibrin 
as  it  did  at  first.  It  is  well  to  keep  an  excess  of  fibrin  always 
in  the  dialyzer.  This  experiment  is  interesting,  because  diges- 
tion in  the  stomach  takes  place  under  somewhat  similar  con- 
ditions, the  peptones  being  absorbed  by  the  gastric  vessels. 
A  stronger  acid  is  required  for  digestion  if  the  products  of  di- 
gestion are  present  in  guanti/;/  in  the  solution.  When  digestion 
stops,  as  in  the  previous  experiment,  it  may  be  renewed  by 
acidulating  the  solution  more  strongly  with  hydrochloric  acid 
instead  of  diluting  with  water,  and  when  it  stops  a  second  time 
a  second  addition  of  acid  will  set  it  on  again.  As  too  strong 
hydrochloric  aeid  arrests  digestion,  a  limit  is  soon  put  to  the 
addition  of  acid,  but  if  phosphoric  acid  is  used  instead,  diges- 
tion may  be  kept  up  for  a  considerable  time  by  fresh  additions 
of  acid. 

*  125.  Pepsin  Test. — The  power  of  pepsin  to  dissolvealbu- 
minous  substances  and  convert  them  into  peptones,  has  been  em- 
ployed as  a  test  for  its  presence.  For  this  purpose  either  fibrin 
or  coagulated  white  of  egg  maybe  used.  The  process  is  given 
by  Briicke  in  "  Moleschotts  Untersuchungen"  for  1860,  p.  490, 
and  from  this  the  following  description  has  been  taken: — 

f  Pepsin  Test  with  Fibrin. — To  test  for  the  presence  of  pep* 
sin  in  any  substance  or  organ  (as  for  example,  any  part  of  the 
digestive  system  of  an  invertebrate  animal),  it  must  be  finely 
divided,  treated  with  distilled  water,  and  then  allowed  to  stand 
for  some  time,  with  frequent  stirring,  and  filtered.  If  the  filtrate 
is  alkaline  it  must  be  neutralized,  after  which  as  much  hydro- 
chloric acid  must  be  added  to  it  as  will  bring  the  percentage 
of  acid  to  one-tenth.  A  bit  of  fibrin  is  then  thrown  into  it;  if 
it  swells  it  is  allowed  to  stand,  but  if  it  does  not  swell,  dilute 
acid  is  added  by  drops  at  intervals  till  the  edges  and  free  fibres 


BY    DR.    LAUDER    BRUNTON.  489 

of  the  hits  of  fihrin  hecome  translucent.  If  the  filtrate  is  acid, 
a  hit  of  fihrin  is  thrown  into  it;  if  it  swells  up,  it  is  allowed  to 
stand,  if  not,  acid  is  added  as  before  directed  till  it  does  swell : 
the  digestion  is  then  allowed  to  go  on  at  the  temperature  of 
the  room,  and  the  result  observed. 

The  residue  which  remains  on  the  filter  is  introduced  into  a 
beaker  covered  with  0.1  per  cent,  hydrochloric  acid,  and  placed 
in  the  water-bath  at  40°  C.  for  an  hour  and  a  half  or  two  hours, 
or  allowed  to  stand  24  hours  at  the  temperature  of  the  room, 
with  frequent  stirring.  It  is  then  filtered,  and  the  filtrate  used 
in  the  same  manner  as  before.  The  reason  why  Briicke  recom- 
mends that  the  watery  extract  should  be  tested  separately  from 
the  acid  extract,  is  that  by  this  means  pepsin  already  excreted 
from  the  peptic  cells  can  be  distinguished  from  pepsin  still  con- 
tained in  them,  inasmuch  as  the  former  is  easily  taken  up  by 
water  alone,  while  the  latter  is  taken  up  with  difficulty  by 
water,  but  easily  by  dilute  acid.  This  process  has  also  the  ad- 
vantage that  when  soluble  albuminous  bodies  are  present  in 
any  quantity,  the}'  are,  for  the  most  part,  removed  by  the 
watery  extract.  If  neither  of  these  objects  is  of  importance, 
the  substance  may  be  at  once  treated  with  dilute  hydrochloric 
acid,  and  when  it  is  small,  as,  for  example,  the  salivary  glands 
of  insects,  it  may  be  at  once  thrown  with  a  bit  of  fibrin  into 
dilute  hydrochloric  acid,  and  digestion  looked  for.  If  a  fluid 
is  to  be  examined  it  must  be  filtered,  and  the  filtrate  and  residue 
treated  as  above  directed  for  solids. 

Pepsin  Test  with  White  of  Egg. — White  of  egg  is  more  readily 
got  than  fibrin,  but  it  dissolves  mere  slowly,  so  that  the  test 
takes  a  longer  time.  Hard  boiled  white  of  egg,  cut  into  dice, 
may  be  left  for  a  long  time  in  dilute  hydrochloric  acid  without 
undergoing  any  changes,  but  the  coagulum  which  is  produced 
by  boiling  white  of  egg  diluted  with  water  undergoes  partial 
solution  pretty  rapidly.  The  free  alkali  contained  in  white  of 
egg  is  the  cause  of  this  difference  in  its -behavior  when  prepared 
in  these  different  ways,  and  the  inconstancy  of  its  amount  ren- 
ders it  difficult  to  determine  what  degree  of  acidity  must  be 
given  to  the  liquid.  To  obviate  this,  add  acetic  acid  to  white 
of  egg  diluted  with  water  until  it  turns  blue  litmus  paper  violet, 
but  not  red.  Filter  from  the  precipitate;  test  the  reaction  of 
the  filtrate  again,  and  correct  it  if  necessary.  Then  coagulate 
it  in  the  water-bath,  wash  it  with  water,  and  use  it  like  fibrin, 
but  iimj  an  acid  of  0.15  per  cent.  If  pepsin  is  present,  diges- 
tion will  go  on  just  as  with  fibrin.  The  acid  alone  will  not  dis- 
solve the  albumin  for  many  days. 

126.  Theory  of  Pepsin  Digestion. — It  has  already  been 
leen  that  neither  pepsin  alone,  nor  hydrochloric  acid  alone, 
will  digest.  0.  Schmidt  supposes  they  do  so  when  mixed,  by 
forming  a  compound  acid — pepto-hydrochloric acid,      lie  thinks 


490  DIGESTION. 

that  digestion  consists  in  the  combination  of  this  acid  with 
albuminous  bodies,  and  explains  the  fact  that  digestion  can 
be  renewed  by  the  addition  of  hydrochloric  acid  after  it  has 
ceased,  by  supposing  that  the  pcpto-hydrochloric  acid,  thus 
liberated,  is  enabled  to  begin  to  digest  anew. 

The  combination  of  pepsin  and  hydrochloric  acid  to  form  a 
new  acid  is  supported  by  several  facts,  and  is  very  generally 
believed,  but  Schmidt's  hypothesis  regarding  its  mode  of 
action  is  open  to  the  objection  that  it  is  not  merely  a  com- 
pound of  albumin  with  acid  which  is  formed  during  digestion, 
but  peptones.  It  therefore  seems  more  probable  that  the  pep- 
sin acts  as  a  ferment  only  in  acid  solutions,  causing  the  albu- 
minous bodies  to  take  up  water  and  split  up.1 

That  pepsin  and  hydrochloric  acid  mutually  combine  when 
mixed,  as  in  digestive  liquids,  is  rendered  probable,  not  only 
by  the  fact  already  shown  that  they  produce  effects  together 
which  neither  is  capable  of  producing  separately,  but  that  in 
such  mixtures  the  characters  of  both  are  modified. 

This  is  seen  by  comparing  the  action  of  dilute  hydrochloric 
acid  alone  with  that  of  hydrochloric  acid  pepsin.  The  former 
extracts  all  the  salts  and  leaves  a  gelatinous  substance,  while 
the  latter  extracts  this  substance  and  leaves  a  brittle  mass 
containing  a  large  proportion  of  inorganic  salts.  As  regards 
pepsin,  a  modification  of  property  is  shown  in  Yon  Wittich's 
observation,  that,  although  pepsin  alone  does  not  diffuse 
through  vegetable  parchment,  pepsin  with  hydrochloric  acid 
does  so  readily.  That  the  decomposition  of  albuminous  sub- 
stances is  essentiall}'  connected  with  their  taking  up  water,  is 
rendered  probable  by  the  fact  that  digestion  does  not  take 
place  in  its  absence,  and  that  products  similar  to  those  of 
digestion  can  be  obtained  by  boiling  albuminous  bodies  with 
water  for  a  very  long,  time,  or  for  a  shorter  time  with  dilute 
acid. 

The  former  of  these  facts  can  be  easily  demonstrated  by 
treating  fibrin  which  has  been  soaked  in  glycerin  and  not 
washed  at  40°  C.  with  a  glycerin  solution  of  pepsin  undiluted 
with  water,  acidulated  to  the  proper  degree  by  the  addition  of 
a  few  drops  of  strong  acid  ;  under  these  circumstances  the 
fibrin  is  not  digested.  The  latter  may  be  shown  by  boiling 
fibrin  with  dilute  sulphuric  acid  for  an  hour  or  two,  and  then 
neutralizing  the  liquid,  filtering  and  testing  the  filtrate  for 
peptones. 

*  127.  Secretion  of  Gastric  Juice. — Pepsin  is  contained 
in  all  parts  of  the  peptic  glands,  but  free  acid  is  only  formed 
near  their  orifices.     To  show  this,  kill  a  pigeon,  open  it  imme- 

1  For  a  clear  account  of  the  probable  mode  of  action  of  ferments,  see 
"  Betrachtungen  iiber  die  Wirkungsweise  der  ungeforinten  Fermente," 
by  Dr.  G.  Hufner ;  Barth,  Leipzig,  1872. 


BY    DR.    LAUDER    BRUNTON.  491 

diately  and  dissect  off  part  of  the  muscular  layer  from  the 
proventriculus,  which  lies  between  the  crop  and  gizzard.  The 
ends  of  the  gastric  glands  are  thus  laid  bare.  With  a  pair  of 
curved  scissors  snip  off  the  ends  of  the  glands,  taking  care  not 
to  cut  much  below  the  surface.  Squeeze  the  shred  so  obtained 
between  two  bits  of  blue  litmus  paper.  It  will  have  a  neutral 
or  at  most  an  extremely  weak  acid  reaction,  while  the  inside 
of  the  stomach  will  be  found  to  be  strongly  acid.  The  pres- 
ence of  pepsin  in  the  part  of  the  glands  where  little  or  no  acid 
is  contained  may  be  shown  by  dissecting  oft*  this  part  along 
with  the  muscular  layer,  and  placing  it  in  a  test-tube  with  0.1 
per  cent,  hydrochloric  acid  in  the  water-bath  at  40°  C.  Part 
at  least  of  the  muscular  la}7er  will  be  digested.  The  presence 
of  acid  only  on  the  surface  of  the  stomach  can  be  shown,  also, 
b}r  injecting  first  a  solution  of  half  a  gramme  of  ferric  lactate, 
and  then  a  solution  of  potassium  ferrocyanide  into  the  jugular 
vein  of  a  rabbit,  killing  it  about  an  hour  afterwards,  and  open- 
ing the  stomach  immediately.  These  two  salts  form  Prussian 
blue  onl}7  in  the  presence  of  an  acid.  On  making  a  section  of 
the  wall  of  the  stomach,  it  is  seen  that  the  blue  color  is  en- 
tirely confined  to  the  surface,  the  deeper  part  of  the  mucous 
membrane  remaining  colorless. 

After  Death  Acid  continues  to  be  formed  in  the  Glands. — 
Thus,  if  the  stomach  of  a  pig  or  rabbit  is  cut  in  pieces,  washed 
until  it  no  longer  gives  a  trace  of  acid  reaction,  and  then  left 
to  itself,  it  is  found  after  a  time  to  be  again  acid. 

*  128.  Digestion  of  the  Stomach  by  itself.— If  there 
is  only  a  small  quantity  of  acid  present  in  the  stomach  it  will 
not  be  completely  digested  after  death  ;  but  if  it  contains 
anything  which  will  supply  acid,  not  only  the  stomach,  but  a 
great  part  of  the  adjoining  organs  may  be  digested.  Give  a 
cat  a  quantity  of  milk,  or  introduce  the.  same  liquid  into  the 
stomach  of  a  rabbit  or  guineapig  by  means  of  a  Byringe  and  a 
gum-elastic  catheter.  For  this  purpose  a  perforated  cork 
should  be  placed  between  the  animal's  teeth,  and  the  catheter 
passed  through  the  hole  into  the  stomach.  In  an  hour  after  kill 
the  animal,  and  let  it  lie  in  a  warm  place  for  twenty-four  hours. 
The  whole  of  the  stomach  will  probabty  be  found  digested. 
The  stomach  is  not  digested  during  life,  because  the  alkalinity 
of  its  walls  is  preserved  by  the  circulation  of  blood  in  them. 

*  129.  Digestion  of  the  Stomach  during  Life. — When 
the  circulation  of  the  blood  is  arrested  in  one  part  of  the  organ, 
it  becomes  digested,  and  ulceration  occurs.  This  is  best  shown 
by  Sharpey's  modification  of  Pavy's  original  experiment.  The 
method  consists  in  opening  the  stomach  of  a  rabbit,  narcotized 
by  subcutaneous  injection  of  chloral,  by  a  longitudinal  incision, 
seizing  a  part  of  its  posterior  wall  with  a  pair  of  artery  forceps 
and  drawing  it  forward.     This  having  been  done,  a  ligature  is 

I 


492  DIGESTION. 

passed  round  the  part  seized,  so  as  to  include  a  piece  of  about 
half  an  inch  in  diameter.  Finally,  the  wound  in  the  stomach 
ami  that  in  the  abdominal  wall  are  sewn  up.  and  the  animal 
placed  in  a  warm  place  for  some  hours. 

130.  Influence  of  Nerves  upon  the  Secretion  of  the 
Stomach. — The  stomach,  like  the  submixillary  gland,  has  two 
secretions;  one  thin,  watery,  and  acid — the  gastric  juice  proper  ; 
the  other  thick,  tenacious  and  alkaline — the  gastric  mucus. 
The  latter  is  secreted  and  accumulates  on  the  surface  of  the 
gastric  mucous  membrane  during  fasting,  while  the  former  is 
only  secreted  when  an  irritant  is  applied  to  the  inside  of  the 
stomach.  The  irritant  may  be  mechanical,  e.  <?.,  the  friction 
caused  by  food,  or  any  firm  or  hard  substance  introduced  into 
the  stomach,  tickling  with  a  feather,  or  rubbing  with  a  glass 
rod.  The  most  active  chemical  irritants  are  alkalies,  which 
produce,  even  in  very  dilute  solutions,  an  abundant  secretion. 
This  continues  even  after  the  alkali  has  been  neutralized  by 
the  gastric  juice  or  washed  away  by  a  stream  of  water.  The 
saliva  which  is  swallowed  by  the  animal  thus  excites  the  se- 
cretion of  gastric  juice.  Other  stimulants  are  alcohol,  ether, 
pepper,  and  cold  water.  When  an  irritant  is  applied, the  gas- 
tric mucous  membrane,  which  is  of  a  pale  color,  immediately 
becomes  red  ;  its  vessels  dilate  those  of  the  submaxillary  gland, 
and  the  watery-looking  gastric  juice  oozes  rapidly  from  its 
surface.  The  nerve  centres,  on  which  secretion  is  dependent, 
are  present  in  the  walls  of  the  stomach  itself,  for  it  takes  place 
even  after  all  the  nerves  which  enter  the  viscus  from  without 
have  been  divided.  These  centres  are,  however,  as  Ave  shall 
see,  much  influenced  by  the  vagi. 

The  Action  of  the  Vagus  on  the  stomach  is  still  much  dis- 
puted, but  it  would  appear  from  the  experiments  of  Bernard 
and  Rutherford  that  it  contains  afferent  fibres,  the  irritation  of 
which,  as,  e.  g.,  during  digestion,  causes  reflex  dilatation  of  the 
gastric  vessels.  Bernard  found  that  section  of  the  vagi  during 
digestion  caused  the  stomach  to  become  pale,  and  that  in  one 
or  more  experiments,  irritation  of  these  nerves  reddened  it,  and 
induced  an  abundant  secretion.  He  did  not,  however,  deter- 
mine whether  this  effect  was  due  to  afferent  or  efferent  fibres, 
but  Rutherford  found  that,  while  section  of  the  vagi  during  di- 
gestion caused  the  stomach  to  become  pale,  irritation  of  their 
central  ends  generally  reddened  it.  This  effect  was,  however, 
sometimes  preceded  by  its  opposite,  the  organ  becoming  pale  at 
first  and  afterwards  red.  a  result  which  indicates  that  the  vagus 
contains  two  sets  of  afferent  fibres,  one  of  which  increases, 
while  the  other  diminishes  the  degree  of  contraction  of  the  gas- 
tric vessels.' 

From  the  observation  of  Bernard  and  Blondlot,  that  gentle  excita- 
tion increases  the  secretion  of  gastric  juice  while  violent  irritation  stops 


BY    DR.    LAUDER    BRUNTON.  493 

**  131.  Effect  of  Stimuli  on  the  Secretion  of  Gastric 
Juice. — To  see  the  effect  of  stimuli  applied  to  the  mucous 
membrane,  a  dog  with  a  gastric  fistula  should  be  allowed  to 
fast  for  six  or  seven  hours,  and  then  laid  on  its  side  in  such  a 
position  that  a  good  light  falls  into  the  canula.  The  observa- 
tion consists  in  noting  the  color  of  the  membrane,  and  then  in- 
jecting a  little  dilute  solution  of  sodium  carbonate,  or  tickling 
the  surface  with  a  feather,  and  observing  the  effect.  The  effect 
of  irritation  on  the  amount  of  secretion  ma}'  be  estimated  by 
letting  the  dog  stand  while  the  beaker  is  held  under  the  canula, 
and  bjr  measuring  the  juice  which  flows  from  it  in  a  given  time 
before  and  after  irritation. 

**  132.  Demonstration  of  the  Action  of  the  Vagus 
and  Splanchnic  on  the  Stomach.— The  proof  that  the 
vasomotor  nerves  of  the  stomach  are  derived  from  the  splanch- 
nics  is  founded  on  the  observation  that,  when  the  left  splanch- 
nic is  irritated  in  the  rabbit,  as  directed  at  page  259,  the  arte- 
ries at  the  great  curvature  may  be  seen  to  contract.  This  may 
be  still  better  seen  in  the  cat. 

The  vagus  is  the  sensory  nerve  of  the  stomach  and  contains 
afferent  fibres,  the  irritation  of  which  produces  reddening  of 
the  gastric  mucous  membrane. — It  also  contains  motor-fibres 
which  are  distributed  to  the  muscular  coats  of  the  organ.  To 
show  these  facts,  a  cat  must  be  placed  under  chloroform,  after 
which  both  vagi  are  prepared,  and  the  stomach  exposed.  If, 
now, the  animal  having  partially  recovered  from  the  anaesthetic, 
the  stomach  is  seized  between  the  thumb  and  forefinger,  and 
subjected  to  traction  in  the  direction  of  its  length,  slight  but 
unequivocal  signs  of  uneasiness  are  perceived.  The  vagi  are 
then  divided,  after  which  it  may  be  observed,  first,  that  the 
stomach  is  paler  than  before,  and  secondly,  no  sign  of  uneasi- 
ness is  produced  b}r  traction. 

On  irritation  of  the  central  end  of  one  of  the  divided  nerves, 
the  color  of  the  mucous  surface  is  more  or  less  completely  re- 
stored. On  irritation  of  the  peripheral  end,  the  walls  of  the 
stomach  often  begin  to  contract,  but  this  effect  is  not  constant 
when  either  splanchnic  is  intact.  When  both  are  divided,  irri- 
tation of  either  vagus  is  invariably  followed  by  movements  of 
the  stomach  (Ilouckgeest). 

Experiments  on  vomiting  have  been  omitted,  as  they  do  not 
succeed  in  narcotized  animals. 

it  and  causes  vomiting,  it  appears  probable  that  some  of  the  gastric  nerves 
are  more  easily  excited  than  others.  See  Carpenter's  Physiology,  edited 
by  Power,  7th  edition,  p.  128. 


494  DIGESTION. 

Section  III. — Functions  of  the  Liver. 


133.  General  Characters  of  the  Bile. — Bile  as  it  flows 
from  the  liver  is  a  thin  liquid,  but  when  it  stays  some  time  in 
the  gall  bladder  it  becomes  mixed  with  mucin,  the  presence  of 
which  renders  it  tenacious.  In  man,  it  is,  when  fresh,  of  a 
golden-yellow  color,  like  yolk  of  egg,  as  may  be  seen  when  it 
is  vomited;  but  after  death  the  bile  in  the  gall  bladder  is 
generally  brownish.  In  the  dog  it  is  also  yellow,  in  the  herbi- 
vora  it  is  green,  but  very  frequently  it  has  a  decided  brown 
tinge  in  both.  Its  specific  gravity  and  composition  are  not 
alwa3rs  the  same  even  in  the  same  animal. 

Sj)ecijic  Gravity  and  Solids. — The  specific  gravity  and 
amount  of  solids,  organic  and  inorganic,  in  bile  are  determined 
in  the  same  way  as  in  saliva.  The  ash  has  a  reddish  tinge, 
due  to  the  presence  of  iron.  For  the  method  of  determining 
the  amount  of  iron,  see  page  202. 

*  Reaction. — Bile  discolors  litmus  so  much  as  to  hide  the 
reaction,  it  must  therefore  be  first  diluted  and  the  reaction 
tested  afterwards.     In  fresh  bile  it  is  always  alkaline. 

134.  Composition  of  Bile. — When  obtained  from  the  gall 
bladder,  the  bile  contains,  1,  mucin  ;  2,  bile  pigments;  3,  sodium 
salts  of  biliary  acids;  4,  cholesterin;  5,  lecithin  ;  6,  phosphates 
of  sodium,  calcium,  and  iron,  sodium  chloride,  and  generally 
traces  of  copper. 

*  Mucin. — Add  common  alcohol  to  bile,  obtained  from  the 
gall  bladder  of  an  ox;  wash  the  abundant  precipitate  so  ob- 
tained with  dilute  alcohol ;  add  water,  and  the  precipitate  will 
dissolve;  add  acetic  acid,  and  a  precipitate  of  mucin  will  fall 
with  traces  of  bile  pigment  adhering  to  it.  For  the  reactions 
of  mucin,  see  §  45. 

Bile  Pigments The  yellow  color  of  fresh  bile  in  man  and 

carnivora  is  due  to  a  coloring  matter  termed  Bilirubin  ;  the 
green  color  possessed  by  the  bile  in  herbivora,  or  acquired  by 
the  bile  of  carnivora  after  standing,  is  due  to  Biliverdin,  a  pro- 
duct of  the  oxidation  of  Bilirubin.  When  the  bile  is  long  in 
the  gall  bladder,  a  small  quantity  of  a  third  pigment,  Biliprasin, 
may  also  be  present. 

**  135.  Test  for  Bile  Pigments  (Gmellin's  Test.)— 
When  strong  nitric  acid,  which  has  been  exposed  to  light,  and 
therefore  contains  nitrous  acid,  is  added  to  a  solution  of  bili- 
rubin, it  becomes  oxidized,  and  the  products  of  oxidation 
which  are  successively  produced,  present  the  colors  of  the 
rainbow.  First,  biliverdin  is  produced,  and  tlte  yellow  color 
of  the  bilirubin  solution  changes  to  green  and  then  becomes 
successively  blue,  violet,  red,  and  lastly  dirty  yellow.     If  a  so- 


BY    DR.    LAUDER    BRUNTON.  495 

lution  of  biliverdin  is  used  instead  of  bilirubin,  the  same 
changes  of  color  occur,  but  the  first  change  is  of  course  to 
blue.  In  the  reaction  above  described,  the  oxidation  is  most 
complete  at  the  point  of  contact  of  the  two  liquids,  the  degree 
of  action  diminishing  as  the  distance  from  this  point  increases. 
If,  therefore,  the  two  liquids  are  brought  into  contact  without 
agitation,  successive  zones  of  color  are  formed  by  the  products 
of  oxidation  in  the  same  order  as  before,  viz.,  green,  blue,  violet, 
red,  and  dirty  ^yellow,  the  last  mentioned  being  nearest  the 
acid.  In  order  to  apply  the  test  to  a  fluid  supposed  to  contain 
bile  pigment,  pour  it  in  a  thin  layer  on  a  white  porcelain  plate, 
and  place  two  or  three  drops  of  nitric  acid  in  contact  with  its 
edge.  Or  pour  nitric  acid  containing  a  little  nitrous  acid  into 
a  test  tube:  hold  it  obliquely,  and  let  the  fluid  to  be  tested 
flow  gently  down  the  side  of  the  test-tube  and  over  the  surface 
of  the  acid.  Fix  the  test-tube  in  the  same  oblique  position, 
without  shaking,  in  a  holder,  and  let  it  stand  ;  see  from  time 
to  time  whether  the  rainbow-colored  zones  have  appeared  at 
the  point  of  junction  in  the  proper  order.  Brucke's  method  is 
to  mix  the  fluid  to  be  tested  with  very  dilute  nitric  acid,  and 
then  to  let  a  little  strong  sulphuric  acid  run  gently  down  the 
side  of  the  test-tube.  Dilute  nitric  acid  alone  does  not  act  on 
the  bile  pigment,  but  after  the  addition  of  the  sulphuric  acid 
t he  colored  rings  spread  from  its  upper  surface.  Ox-gall  does 
not  exhibit  the  colored  zones,  even  when  treated  with  strong 
nitric  acid,  unless  it  contains  much  nitrous  acid. 

To  show  them,  pour  a  little  ox-bile  on  one  part  of  a  porce- 
lain plate,  and  on  another  near  it  some  very  strong  nitric  acid, 
containing  much  nitrous  acid,  or  nitric  acid,  previously  mixed 
with  concentrated  sulphuric  acid,  and  let  the  bile  and  acid 
gently  come  in  contact.1 

1  When  the  urine  of  a  patient  suffering  from  jaundice  is  tested  for 
bile  pigments  with  nitric  acid,  the  color  reaction  sometimes  cannot  be 
obtained,  even  though  the  urine  be  so  dark  that  the  foam  on  its  surface, 
after  shaking  it,  is  quite  yellow.  Tins  negative  result  generally  occurs 
in  cases  where  the  temperature  of  the  patient  is  high,  and  more  espe- 
cially when  it  has  continued  high  for  some  time.  It  is  then  advisable, 
instead  of  testing  the  urine  directly  with  nitric  acid,  to  use  the  method 
recommended  by  Huppert.  Precipitate  the  urine  with  milk  of  lime, 
throw  the  precipitate  on  a  fluted  filter,  and  allow  the  fluid  to  drain  away. 
Take  a  piece  of  the  precipitate,  about  the  size  of  half  a  hazel-nut,  place 
it  in  a  test-tube,  fill  the  tube  half  full  of  alcohol,  and  then  add  dilute 
sulphuric  acid  in  such  quantity  that  the  fluid,  after  being  shaken,  has  an 
acid  reaction.  Warm  the  tube  :  the  fluid  will  extract  the  color  from  the 
precipitate  ;  filter  and  boil  the  filtrate.  If  bilirubin  is  present  in  the 
urine,  it  will  combine  with  the  lime  and  be  precipitated  ;  but  it  will  be 
again  set  tree  by  the  sulphuric  acid,  and  be  dissolved  by  the  warm  aci- 
dulated alcohol,  forming  a  yellowish-^reen  solution.  This  solution  will 
become  dark  green  on  boiling,  anil  tin;  more  free  acid  present,  the  sooner 
will  it  do  so.     When  long  boiled,  it  sometimes  becomes  blue. 


496  DIGESTION. 

Fallacies  to  be  avoided  in  using  Gmelin's  Test. — This  test 
must  never  be  applied  to  a  fluid  containing  alcohol,  as  the 
alcohol  alone  will  cause  abundant  formation  of  nitrous  acid, 
and  produce  the  colored  rings,  although  no  bile  pigment  is 
present. 

Jn  using  it  for  the  detection  of  bile  pigment  in  urine,  the 
presence  of  indican  may  lead  to  error.  This  is  avoided  if  care 
is  taken  to  observe  that  the  green,  violet,  and  red  zones  are  all 
present,  as  urine  containing  much  indican  may  exhibit  green 
and  yellow  zones  alone,  or  green  and  yellow  with  blue  between, 
but  never  exhibit  all  of  the  colors  in  the  right  order. 

*  136.  Bilirubin.  ClfiH18N,();.  —  Synonymes  :  Bilifulvin, 
Biliphain,  Cholepyrrhin,  Haematoidin. 

Preparation  from  Bile. — Put  some  fresh  dog's  bile  in  a 
small  flask,  acidulate  it  with  acetic  acid,  add  chloroform  till 
the  flask  is  almost  full,  warm  it  in  a  water-bath,  and  shake. 
The  chloroform  takes  up  the  bilirubin  and  settles  at  the  bot- 
tom of  the  flask.  Remove  it  with  a  pipette,  and  evaporate  it 
quickly.  The  red  residue  is  bilirubin.  Add  alcohol  to  it  to 
dissolve  out  the  impurities  ;  pour  it  off  after  it  has  stood  some 
time  ;  dissolve  the  bilirubin  again  in  chloroform,  and  again 
evaporate.  To  obtain  it  pure,  this  may  be  repeated  once  or 
twice.  When  crystallized,  it  is  of  a  red  color.  During  crys- 
tallization, a  part  of  it  is  apt  to  become  oxidized  with  biliver- 
din,  on  which  account  it  is  easier  to  obtain  it  pure  by  precipi- 
tating it  from  the  choloroform  solution  by  the  addition  of 
alcohol.  The  precipitate  is  amorphous,  and  of  an  orange 
color. 

The  amount  of  bilirubin  which  can  be  obtained  from  the 
bile  of  a  single  dog  is  very  small.  To  obtain  it  in  greater 
quantities,  biliary  calculi  may  be  used. 

Preparation  of  Bilirubin  from  Gall  Stones. — Reduce  the 
gall  stone  to  powder,  and  extract  it  first  with  ether,  to  free  it 
lrom  fat  and  cholesterin,  so  long  as  any  of  the  powder  is  dis- 
solved;  next  boil  it  with  water,  to  free  it  from  admixture  of 
bile ;  and  lastly,  treat  it  with  dilute  hj^drochloric  acid,  to 
remove  lime  and  magnesia.  Dissolve  the  residue  in  warm 
chloroform.  Filter  (preserving  the  undissolved  part),  distil, 
or  evaporate  off  the  chloroform  ;  extract  the  residue  with  abso- 
lute alcohol  (preserving  the  alcoholic  extract,  see  §  147),  and 
then  witli  ether.  Dissolve  the  residue  in  a  second  quantity  of 
chloroform,  and  evaporate  until  the  bilirubin  begins  to  sepa- 
rate, and  then  precipitate  it  with  alcohol. 

Properties  of  Bilirubin. — The  orange-colored  precipitate  is, 
1,  quite  insoluble  in  water;  2,  very  slightly  soluble  in  ether; 
3,  springly  soluble  in  alcohol,  but  rather  more  soluble  than  in 
ether ;  4,  soluble  in  chloroform,  especiall}'  when  warm,  and  in 
a  less  degree  in   benzol  and   bisulphide  of  carbon,  amyl-alco- 


BY    DR.    LAUDER    BRUNTON.  497 

hol,  and  glycerin.  Its  solutions  have  a  yellow  or  brownish-red 
color,  which  is  so  intense  that  it  is  distinguishable  in  a  layer 
1.5  centimetres  thick  of  a  solution  containing  one  part  in 
500,000. 

Bilirubin  combines  with  alkalies,  forming  compounds  which 
are  soluble  in  weak  alkaline  liquids,  which  are  precipitated  by 
neutralization.  They  are  insoluble  in  chloroform,  the  chloro- 
form solution  bilirubin  being  precipitated  by  alkalies.  For 
this  reason  it  is  necessary  to  acidity  bile  before  extracting  the 
bilirubin  with  chloroform.  Bilirubin  also  combines  with  Lime. 
— If  bilirubin  is  dissolved  in  ammonia,  and  the  solution  pre- 
cipitated with  calcium  chloride,  a  rusty-red  flocculent  precipi- 
tate is  obtained,  which  is  a  calcium  compound  of  bilirubin. 

*  137.  Biliverdin.  C16H20N.,O,  or  C^H^N^.— Preparation. 
— Put  an  alkaline  solution  of  bilirubin  in  a  flat  shallow  vessel, 
and  let  it  stand  exposed  to  the  air  for  a  considerable  time, 
until  it  becomes  green.  Precipitate  it  with  hydrochloric  acid, 
wash  the  precipitate  with  water,  dissolve  it  in  alcohol,  filter, 
and  evaporate.  The  biliverdin  is  left  as  an  amorphous  body. 
The  reaction  by  which  bilirubin  is  converted  into  biliverdin  is 
considered  by   Staedeler  to  be  CI6HlfeN2O3-|-H,O-|-O  =  C16H.0 

NsOs« 

Properties. — It  is  insoluble  in  water,  ether,  and  chloroform. 
It  is  soluble  in — 1,  alcohol  (and  can  thus  be  separated  from 
bilirubin,  which  is  insoluble),  2,  dilute  liquor  potassae,  or  3, 
ammonia,  and  4,  strong  sulphuric  acid.  It  is  precipitated  from 
its  alkaline  solution  by  acids,  or  by  salts  of  calcium,  barium, 
or  lead.  It  is  precipitated  unchanged  from  its  solution  in  sul- 
phuric acid  by  the  addition  of  water.  Nitric  acid  oxidizes  bili- 
verdin in  alkaline  solutions,  and  produces  the  same  series  of 
colors  as  with  bilirubin.  Sulphurous  acid,  which  is  a  powerful 
deoxidizing  agent,  causes  alkaline  solutions  of  biliverdin,  espe- 
cially when  warmed,  to  become  yellow  ;  when  the  j'ellow  solu- 
tion is  treated  with  nitric  acid,  it  behaves  just  like  a  solution 
of  bilirubin. 

138.  Relation  of  Bile  Pigments  to  Haemoglobin. — Bili- 
rubin is  generally  believed  to  be  formed  from  haemoglobin, 
which  becomes  altered  during  the  passage  of  blood  through 
the  liver.  The  grounds  for  this  belief  are  the  apparent  identity 
of  bilirubin,  and  the  pigment  called  haematoidin,  found  in  old 
extravasations  of  blood,  and  the  observation  that  bile  pigments 
appear  in  the  urine  after  the  injection  into  the  veins  of  solu- 
tions of  haemoglobin  or  of  any  substance  which  will  dissolve 
the  blood  corpuscles,  and  liberate  haemoglobin,  such  as  water 
(Herrmann),  bile  acids  (Frerichs  Kiihne),  or  ether  (Tiegel). 
They  also  appear  after  prolonged  inhalation  of  ether  (Noth- 
nagel),  or  chloroform  (Bernstein).  Further  support  is  also 
lent  to  this  view  by  the  destruction  of  haemoglobin,  which 
32 


498  DIGESTION. 

appears  to  take  place  in  the  blood  during  its  passage  through 
the  liver  (Grehant).  Though  a  positive  result  has  been 
obtained  by  so  many  observers,  Naunyn  failed  to  detect  bile 
pigments  in  the  urine  of  rabbits  after  the  injection  of  haemo- 
globin, either  subcutaneously  or  into  the  jugular  vein,  and 
attributed  the  success  of  others  to  their  experiments  having 
been  made  on  dogs,  in  whose  urine  bile  pigment  is  normally  of 
frequent  occurrence.  Tie  noticed  them,  however,  in  rabbit's 
urine,  when  blood  in  which  the  corpuscles  had  been  destroyed 
by  freezing  or  ether,  was  injected  into  the  intestine,  so  that 
the  haemoglobin  absorbed  from  it,  or  set  free  by  the  action  of 
the  ether  on  the  blood  of  the  portal  vein,  passed  through  the 
liver  before  reaching  the  general  circulation.  Nannyn's  experi- 
ments, also,  have  been  repeated  by  Wolff  and  Wickham  Legg, 
with  a  negative  result. 

In  performing  them  proceed  as  follows:  Narcotize  a  rabbit 
with  chloroform,  shave  the  hair  from  the  belly,  make  an  incision 
about  1^  centimetres  in  length  in  the  linea  alba  a  little  above 
the  middle  point,  between  the  base  of  the  xiphoid  cartilage  and 
the  symphysis  pubis.  Seize  a  coil  of  small  intestine  with  a  pair 
of  artery  forceps,  and  hold  it  opposite  the  wound,  without  draw- 
ing it  forward  more  than  is  just  necessaiy.  Inject  2  cub.  cent, 
of  ether  into  the  intestine  close  to  the  points  of  the  forceps  with 
a  subcutaneous  syringe.  Tie  a  ligature  round  the  point 
wounded  by  the  syringe  and  forceps  ;  attach  the  intestine  by 
it  to  the  abdominal  wall,  and  close  the  wound  with  a  point  of 
suture.  The  inhalation  of  chloroform  is  too  short  to  produce 
of  itself  bile  pigment  in  the  urine,  and  it  greatly  facilitates  the 
operation.1  Examine  the  urine  of  the  rabbit  for  bile  pigments 
an  hour  or  two  after  the  operation,  and  again  next  morning. 
To  get  the  urine,  hold  the  rabbit  over  a  large  beaker,  compress 
the  abdomen  with  the  palm  of  one  hand,  and  press  with  the 
thumb  of  the  other  on  the  bladder  just  above  the  pubes,  push- 
ing it  well  down  into  the  pelvis. 

139.  Relation  bet-ween  the  Coloring  Matter  of  Bile 
and  that  of  Urine. — The  urinary  pigment  is  supposed  to  be 
derived  from  that  of  bile,  as  a  substance  which  presents  similar 
spectroscopic  characters  can  be  extracted  from  bile,  or  produced 
by  deoxidation  from  bilirubin.  In  the  organism,  bile  pigments 
are  probably  reduced  by  hydrogen,  or  other  reducing  agents 
present  in  the  intestine. 

When  dog's  bile  is  extracted  with  dilute  hydrochloric  acid 
and  filtered,  the  filtrate  has  a  reddish  or  reddish-yellow  color, 
and  on  spectroscopic  examination  presents  a  band  close  to  F, 

1  The  writer  has  failed  to  observe  bile  pigments  in  the  urine,  either 
after  the  injection  of  bile  acids  into  the  veins,  or  of  ether  or  dissolved 
blood  corpuscles  into  the  intestines. 


BY    DR.    LAUDER    BRUNTON.  499 

between  it  and  5,  which  disappears  on  the  addition  of  liquor 
sodae,  and  is  replaced  by  a  narrower  band,  also  between  6  and 
F,  but  nearer  6,  the  filtrate  at  the  same  time  assuming  a  yel- 
lowish color.  If  the  solution  is  only  very  slightly  alkaline, 
both  bands  ma}T  be  seen  at  once.  .  Ammonia  produces  similar 
changes  in  the  color  of  the  fluid,  but  the  second  band  is  very 
faint  when  it  is  employed.  On  acidulation,  the  alkaline  liquid 
regains  its  red  color,  and  the  first  band  re-appears.  By  treat- 
ing it  with  chloroform,  a  solution  is  obtained  in  which  the  first 
band  is  visible,  but  is  somewhat  nearer  b. 

Urine,  especially  when  high-colored,  exhibits  the  band  at  F, 
though  not  very  distinctly;  but  it  may  be  clearly  seen  by  pre- 
cipitating the  urine  with  lead  acetate,  decomposing  the  precipi- 
tate by  an  acid,  and  examining  the  filtrate  spectroscopicallj\ 
The  addition  of  sodium  hydrate  causes  the  other  band  faintly 
to  appear,  and  when  treated  with  .chloroform  in  the  same  way 
as  bile,  the  solution  and  the  position  of  the  band  seen  in  the 
chloroform  solution  is  altered  in  a  similar  manner. 

A  substance  presenting  a  similar  band  is  obtained  by  acting 
on  a  solution  of  bilirubin  in  liquor  potassse  or  liquor  sodae  with 
sodium  amalgam,  for  several  days,  with  exclusion  of  air  (Maly). 

**  140.  Bile  Acids. — The  bile  acids  are  taurocholic  and 
glycocholic  acids.  In  the  bile  of  the  pig  another  acid,  hyocho- 
lic  acid,  is  present.  In  the  bile  they  are  combined  with  soda, 
and  their  soda  salts  form  the  so-called  crystallized  bile.  These 
acids  are  conjugate  acids,  composed  of  cholic  acid  in  combina- 
tion with  taurine  and  glycocine.  The  presence  of  cholic  acid 
or  its  compound  is  recognized  by  a  reaction  known  as 

Pettenkofer's  Test. — This  test  shows  the  presence  only  of 
bile  acids,  but  not  of  bile  pigments  or  other  constituents  of  bile. 
Dilute  some  ox-bile  with  water  and  filter  it.  Put  a  little  in  a 
test-tube,  with  a  small  piece  of  sugar  or  a  little  strong  syrup. 
Then  add  concentrated  sulphuric  acid  drop  by  drop,  shaking 
the  tube  after  each  addition  ;  the  temperature  of  its  contents 
should  be  kept  as  near  70°  C.  as  possible,  either  by  warming  it 
if  necessaiy,  or  putting  it  in  cold  water  if  it  gets  too  hot. 
Cholic  acid  is  first  precipitated  and  then  dissolved  by  the  sul- 
phuric acid,  the  solution  assuming  a  cherry-red  and  then  a 
beautiful  purple  color,  which  becomes  gradually  darker  when 
the  liquid  is  allowed  to  stand.  The  reaction  is  hindered  by 
the  presence  of  much  pigment,  oxidizing  substances,  and  albu- 
minous bodies,  or  bodies  readily  decomposed  by  sulphuric  acid. 
It  is  therefore  better  to  use  a  solution  of  crystallized  bile,  if  it 
is  at  hand,  than  diluted  bile.  This  reaction  cannot  be  relied 
on  alone  as  positive  proof  of  the  presence  of  bile  acids,  for 
amylic  alcohol  and  other  organic  substances  give  a  similar  col- 
oration. To  show  this,  put  a  solution  of  albumin,  or  rather  of 
syntonin  (§  7),  into  a  test-tube  with  a  little  syrup,  and  add 


500  DIGESTION. 

strong  sulphuric  acid.  A  purple  color  is  developed.  To  dis- 
tinguish between  the  purples  given  by  bile  and  by  albumin,  ex- 
amine the  test-tubes  by  the  spectroscope.  The  bile  acids  give 
four  hands;  the  first  at  I),  the  second  and  third  between  D  and 
E  (the  second  being  nearer  I),  the  third  close  to  E),  the  fourth 
at  F.  If  the  solution  is  dilute,  the  third  band  is  seen  sharply, 
the  second  less  distinctly,  and  the  other  indistinctly.  The  col- 
ored albuminous  solution  gives  only  one  band  between  E  and  F. 

Detection  of  Bile  Acids  in  the  Urine. — They  are  usually 
present  only  in  small  quantities  in  the  urine,  even  in  severe 
cases  of  jaundice.  Various  methods  of  applying  Pettenkofer's 
test  have  been  proposed,  one  of  which  (Strassluirg's)  is  applied 
as  follows:  Add  a  little  cane  sugar  to  some  urine  containing 
bile  acids,  dip  a  piece  of  filtering  paper  into  it,  let  it  dry  com- 
pletely, put  a  drop  of  pure  sulphuric  acid  upon  it,  and  allow 
the  acid  partially  to  run  off..  In  a  quarter  of  a  minute  a  beau- 
tiful violet  color  appears,  which  is  best  seen  by  holding  up  the 
paper  to  the  light  and  looking  through  it.  In  all  doubtful 
cases,  and  whenever  accurate  results  are  required,  the  bile 
acids  should  be  separated  before  applying  the  test,  see  §  204. 

*  141.  Crystallized  Bile. — Mode  of  Preparation. — 
Evaporate  bile  to  a  quarter  of  its  volume,  mix  it  with  a  con- 
siderable quantity  of  animal  charcoal,  rub  them  thoroughljr 
together,  and  then  heat  the  mixture  on  a  water-bath  till  it  is 
perfectly  dr}'.  Put  it  immediately,  while  still  warm,  into  a 
flask,  cover  it  with  absolute  alcohol,  cork  the  flask,  and  let  it 
stand  for  a  good  while,  shaking  it  occasionally  so  that  the 
alcohol  may  dissolve  out  all  the  bile  salts.  Filter,  and  pour 
the  filtrate  into  a  perfectlj7  dry  stoppered  bottle,  large  enough 
to  hold  four  times  as  much.  Add  ether  to  it,  until  no  further 
precipitate  is  produced  ;  then  replace  the  stopper,  and  put  the 
bottle  aside  for  a  few  days.  If  the  alcohol  and  ether  are  both 
anhydrous,  the  precipitate  which  falls  consists  of  microscopic 
crystals,  but  generally  it  forms  a  resinous  mass  at  the  bottom 
of  the  flask,  which  after  several  days,  or  weeks,  begins  to 
crystallize,  and  groups  of  silky  needles  appear. 

To  preserve  the  crystals,  pour  off  the  mixture  of  alcohol  find 
ether,  wash  them  with  pure  ether,  evaporate  the  adhering  ether 
from  them  in  vacuo,  and  replace  the  stopper  in  the  bottle. 
The  crystals,  if  left  exposed,  take  up  moisture,  and  form  a 
resinous  mass,  which  is  eventually  converted  into  a  syrupy 
fluid.  Crystallized  bile  is  very  soluble  in  water  and  in  alco- 
hol, hut  insoluble  in  ether. 

Composition  of  Crystallized  Bile Crystallized  bile  consists 

of  the  sodium  salts  of  glycocholic  and  taurocholic  acids.  To 
separate  these  two  acids  from  the  base  and  from  eaeli  other, 
dissolve  the  ciTstals  or  the  resinous  precipitate  in  water,  and 
add  first  solution  of  neutral  lead  acetate,  and  then  a  little  basic 


BY    DR.    LAUDER    BRUNTON.  501 

lead  acetate.  This  combines  with  the  glycocholic  acid,  and 
forms  an  insoluble  lead-glycocholate.  Filter,  and  add  to  the 
filtrate  lead  acetate  and  ammonia,  and  a  precipitate  of  lead- 
tanrocholate  will  be  formed.  Filter;  the  filtrate  contains  the 
soda  which  has  been  set  free,  and  also  the  excess  of  lead. 
The  nature  of  the  base  may  be  shown  by  precipitating  the 
lead  from  the  solution  by  hydrogen-sulphide,  and  filtering  ; 
the  filtrate  when  evaporated  to  dryness  leaves  sodium  acetate. 

*  142.  Glycocholic  Acid  (C2RH45NOH)  is  abundant  in 
ox-gall,  but  is  only  present  in  small  quantities  in  human  bile, 
and  absent  from  the  bile  of  the  dog  and  cat.  Preparation. — 
Dissolve  the  lead-gl3'cocholate  obtained  in  last  experiment  in 
hot  alcohol ;  precipitate  the  lead  with  hydrogen-sulphide,  con- 
centrate the  alcoholic  solution  by  evaporation,  and  then  pre- 
cipitate the  glycocholic  acid  by  adding  water. 

Another  and  easier  plan  is  that  of  Gorup-Besanez.  Evapo- 
rate ox-gall  nearly  to  dryness  in  a  water-bath,  and  exhaust 
the  residue  with  alcohol  of  ninety  per  cent.  (sp.  gr.  822). 
Distil  or  evaporate  off  the  alcohol,  dilute  the  residue  if  neces- 
sary with  water,  add  milk  of  lime  to  it  and  warm  it  gently. 
The  greater  part  of  the  coloring  matter  will  be  precipitated  by 
the  lime.  Filter,  allow  it  to  cool,  and  add  dilute  sulphuric 
acid  to  it  (avoiding  excess),  until  a  permanent  turbidity  is 
produced.  Let  it  stand  for  a  few  hours,  and  the  fluid  will  in 
most  cases  become  a  mass  of  crystals  of  glycocholic  acid. 
Occasionally  this  conversion  does  not  take  place  till  after 
some  days,  or  even  weeks.  Throw  the  mass  on  a  filter  con- 
nected with  the  water  air-pump,  wash  with  cold  water,  and 
press  it  between  folds  of  blotting  paper,  first  with  the  hand 
and  then  with  a  screw-press.  It  may  be  obtained  in  a  still 
purer  condition  by  dissolving  it  in  a  large  quantity  of  lime- 
water,  and  adding  dilute  sulphuric  acid  until  the  ghycocholic 
acid  again  separates.  It  crystallizes  in  long  thin  white  needles. 
The  crystals  are  sparingly  soluble  in  cold  water,  more  readily 
in  warm,  from  which  it  crystallizes  out  on  cooling.  It  is  Tery 
sparingly  solid  tie  in  ether,  readity  in  alcohol.  When  water  is 
added  to  the  alcoholic  solution,  the  acid  is  precipitated  first 
as  a  turbidity,  and  then  in  flakes  and  drops,  which  become 
gradually  con  verted  into  crystals. 

*  143.  Glycocine  or  Glycocol. — Glycocholic  acid  can 
be  decomposed,  and  glycocine  obtained  from  it  by  boiling  it 
for   a    long  time  with    strong    hydrochloric  acid.1     On    then 

'  Glycocine  is  more  readily  prepared  from  hippuric  acid,  which  is 
contained  in  large  quantities  in  the  urine  of  herbivora,  and  consists  of 
glycocine  in  combination  with  benzoic  acid.  Preparation,  of  Hippuric 
Acid.  —  Milk  of  lime  is  added  to  horse's  or  cow's  urine  ;  the  mixture  is 
boiled,  filtered,  neutralized  with  hydrochloric  acid,  and  evaporated  to 
a  small  bulk.     On  acidulating  with  hydrochloric  acid,  hippuric  acid 


502  DIGESTION. 

allowing  it  to  eooi,  a  resinous  mass  (cholalic  acid  and  dyslysin) 
separates.  The  fluid  is  poured  off  from  the  resin  and  evapo- 
rated. The  residue  is  then  dissolved  in  water  wanned  with 
hyd rated  lead  oxide,  and  filtered  ;  the  filtrate  decomposed  by 
hydrogen-sulphide,  filtered,  and  the  filtrate  evaporated. 

The  transparent  rhomboidal  crystals  of  glycocine  thus  ob- 
tained are  then  washed  with  absolute  alcohol.  They  have  a 
sweet  taste,  and  are  readily  soluble  in  cold  water  ;  almost  in- 
soluble in  ether  and  alcohol. 

*  144.  Taurocholie  Acid  (C2fiH45NS07)  is  present  along 
with  glycocholic  acid  in  ox-bile  ;  it  is  the  chief  acid  in  human 
bile,  and  the  only  one  in  that  of  dogs.  Preparation Sus- 
pend the  lead  taurocholate  obtained  from  crystallized  bile  in 
alcohol,  and  decompose  it  by  hydrogen-sulphide  :  filter  ;  evapo- 
rate the  filtrate  at  a  moderate  temperature  to  a  small  bulk, 
place  it  in  a  stoppered  bottle,  and  precipitate  by  a  great  excess 
of  ether.  The  acid  is  precipitated  as  a  syrup.  After  standing, 
it  changes,  if  the  process  is  successful,  to  fine  silky  crystals, 
which,  when  exposed  to  air,  dissolve,  or  form  a  syrup. 

Taurocholie  acid  is  soluble  in  water  and  alcohol,  insoluble 
in  ether.  It  is  recognized  as  a  bile  acid  by  giving  Petten- 
kofer's  reaction,  and  is  distinguished  from  glycocholic  acid 
by  not  being  precipitated  by  lead  acetate  alone,  but  by  lead 
acetate  and  ammonia,  and  from  any  other  bile  acid  b}'  yielding 
taurin  when  decomposed  by  boiling  with  hydrochloric  acid. 
It  may  be  prepared  from  taurocholie  acid  or  from  crude  bile. 

145.  Taurine  (C2H.NS03). — Preparation. — Boil  ox-gall 
with  dilute  hydrochloric  acid  for  several  hours.  The  bile 
acids  are  thus  decomposed  :  Taurine  and  glycocine  combine 
with  the  hydrochloric  acid,  and  remain  in  solution,  cholic  acid 
separating  as  a  resinous  mass.  Filter  the  fluid,  evaporate  the 
filtrate  to  dryness,  extract  the  residue  with  absolute  alcohol  to 
remove  the  glycocine-hydrochlorate,  dissolve  the  residue  in 
water,  and  allow  it  to  stand  and  crystallize.  In  order  to 
purify  it,  dissolve  it  in  spirit,  precipitate  it  with  lead  acetate, 
decompose  the  precipitate  with  hydrogen-sulphide,  filter,  evapo- 
rate the  filtrate  to  dryness,  extract  the  residue  with  absolute 
alcohol,  dissolve  the  taurine  which  remains  in  a  very  little 
water,  and  allow  it  to  crystallize.     Taurine  is  soluble  in  fifteen 

crystallizes  out  in  rhombic  prisms  resembling  thick  needles  (fig.  318). 
Glycocine  is  prepared  by  boiling  hippuric  acid  with  strong  hydrochloric 
acid  for  several  liours,  and  evaporating  tbe  solution  almost  to  dryness. 
The  hippuric  acid  is  decomposed,  yielding  benzoic  acid  and  glycocine. 
The  residue  is  extracted  with  cold  water,  which  dissolves  but  little  of 
the  benzoic  acid.  To  the  watery  extract  hydrated  lead  oxide  is  then 
added,  to  remove  the  hydrochloric  acid.  The  liquid  is  filtered,  and  the 
lead  precipitated  from  the  filtrate  by  hydrogen  sulphide.  The  precipi- 
tate having  been  removed  by  filtration,  the  filtrate  is  evaporated  to  a 
small  bulk. 


BY    DR.    LAUDER    BRUNTON.  503 

or  sixteen  parts  of  cold  water,  and  in  a  much  smaller  quantity 
of  hot  water.  In  cold  alcohol  it  is  sparingly  soluble,  more 
easily  in  warm  alcohol.  It  is  insoluble  in  absolute  alcohol  and 
ether.  Taurine  is  recognized  by  its  crystalline  form,  and  by 
its  containing  sulphur.  Its  crystals  are  colorless,  transparent, 
six-sided  prisms,  with  four  to  six-sided  pointed  ends  (fig.  312). 
Taurine  is  proved  to  contain  sulphur  as  follows:  If  a  crystal 
is  heated  on  platinum  foil,  it  swells,  becomes  brown,  and  fuses, 
giving  off  fumes  in  which  sulphurous  acid  is  recognized  by 
its  smell.  If  the  crystals  are  ignited  with  sodium  carbonate, 
and  a  little  acid  is  poured  over  the  residue,  hydric-sulphide  is 
evolved.  If  they  are  dissolved  in  caustic  potash,  and  the 
solution  concentrated  by  boiling,  ammonia  is  given  off,  and 
potassium  sulphate  and  acetate  left  in  solution. 

146.  Cholic  Acid  (C.>tHm05).  —  Preparation.— Boil  bile 
(or  solution  of  gtycocholic  acid)  with  strong  solution  of  caustic 
potash,  or  hot  saturated  solution  of  baryta  water,  for  twelve 
or  fourteen  hours,  precipitate  by  hydrochloric  acid,  wash  the 
precipitate  with  water,  dissolve  it  in  a  little  liquor  potassre, 
add  ether,  precipitate  by  hydrochloric  acid,  and  allow  the 
liquid  to  stand  for  several  days.  The  ether  causes  it  to  become 
crystalline,  and  form  quadrilateral  prisms  with  pyramidal  ends. 
Pour  off  the  ether,  dry  the  crystals  between  folds  of  blotting 
paper,  dissolve  them  in  hot  alcohol,  and  add  a  little  water 
until  a  turbidity  just  commences.  Cholic  acid  crystallizes 
out  on  cooling  in  tetrahedra.  Cholic  acid  exists  in  two  con- 
ditions. In  one  it  is  soft  and  waxy,  and  somewhat  soluble  in 
water  ;  in  ether  tolerably,  and  in  alcohol  very  readily  soluble. 
In  the  crystalline  condition  it  is  insoluble  in  water  and  ether, 
but  tolerably  soluble  in  alcohol.  When  heated  on  platinum 
foil,  it  becomes  brown,  melts  and  burns,  giving  off  incense-like 
fumes.  Heat,  or  boiling  with  sulphuric  acid,  converts  it  into 
resinous-looking  substances,  choloidinic  acid  and  dyslysin. 

*  147.  Cholesterin. — Cholesterin  is  not  generally  pre- 
pared directly  from  bile,  but  from  gall-stones,  most  of  which 
consist  chiefh'  of  cholesterin,  along  with  a  little  bile  pigment 
and  earthy  salts.  Preparation. — Extract  pulverized  gall- 
stones with  boiling  alcohol,  and  filter  while  boiling.  Crystals 
of  cholesterin  separate  from  the  filtrate  when  cool.  In  order 
to  purify  it,  boil  the  crystals  with  alcoholic  solution  of  caustic 
potash.  On  cooling  they  will  again  separate.  Wash  the  pro- 
duct .with  cold  alcohol,  and  then  with  water;  dissolve  it  in  a 
mixture  of  alcohol  and  ether;  allow  it  to  evaporate.  Crystal- 
lized cholesterin  forms  rhombic,  plates,  the  corners  of  which 
are  often  broken  (fig.  314).  It  is  quite  insoluble  in  water  and 
in  cold  alcohol.  In  boiling  alcohol  it  dissolves  with  ease.  Cho- 
lesterin may  be  conveniently  prepared  from  the  ethereal  extract 
of  gall  stones  obtained  in  the  preparation  of  bilirubin  by  evapo- 


504  DIGESTION. 

ration.  The  crystals  must  be  purified  as  above  directed. 
Reactions. — (1)  Put  a  few  crystals  of  cholesterin  under  the 
microscope  ;  add  a  drop  of  a  mixture  of  Ave  volumes  of  sul- 
phuric acid  and  one  of  water,  and  warm  the  object-glass  gently. 
The  edges  of  the  crystals  will  acquire  a  carmine  color.  If 
three  parts  of  acid  arc  used  to  one  of  water,  the  edges  are 
violet,  and  if  it  is  still  more  dilute  they  become  lilac  and  dis- 
solve in  the  acid.  (2)  Add  to  some  crystals  strong  sulphuric 
acid,  with  a  little  iodine  or  zinc  chloride  ;  they  acquire  a  tint 
which  varies  from  greenish-blue  to  violet.  (3)  Put  a  drop  of 
concentrated  nitric  acid  on  a  costal  in  a  porcelain  capsule, 
and  evaporate  to  dryness  at  a  gentle  heat ;  touch  the  residue 
with  a  drop  of  ammonia.  A  deep  red  color  is  produced.  (4) 
Rub  up  cholesterin  with  strong  sulphuric  acid,  and  add  chlo- 
roform. A  solution  varying  in  color  from  blood-red  to  purple 
is  produced,  which,  after  changing  successively  into  violet, 
blue,  and  green,  finally  disappears. 

*  148.  Action  of  Bile. — The  bile  appears  to  aid  the  ab- 
sorption of  fat.  Lenz,  Bidder,  and  Schmidt  found  that,  after 
ligature  of  the  gall  duct,  a  dog  absorbed  less  fat  than  before, 
and  that  the  chyle  in  the  thoracic  duct  contained  veiy  little 
fat.  They  calculated  the  amount  absorbed  by  comparing  the 
quantity  of  fat  eaten  with  the  amount  passed  with  the  freces. 
The  bile  emulsionizes  fat,  as  can  be  seen  by  shaking  a  little  oil 
with  it.  It  is  doubtful,  however,  whether  it  is  to  this  property 
that  the  absorption  is  due.  In  forcing  oil  through  animal  mem- 
branes or  filter-paper,  either  by  pressure  or  by  suction,  it  passes 
with  much  greater  facility  if  it  has  been  previously  mixed  with 
bile. 

149.  Bile  precipitates  Syntonin  and  Pepsin. — Digest 
a  piece  of  fibrin  with  artificial  gastric  juice,  and  then  add  a 
large  quantity  of  bile  to  it;  a  precipitate  is  at  once  produced. 
Filter,  put  another  piece  of  fibrin  in  the  filtrate,  and  acidulate 
with  hydrochloric  acid  to  the  proper  degree.  The  pepsin  having 
been  precipitated,  the  fibrin  is  not  digested.  Unless  the  quan- 
tity  of  bile  is  large,  the  whole  of  the  pepsin  will  not  be  thrown 
down.  It  is  not  known  what  purpose  is  served  by  the  pre- 
cipitation of  the  chyme  by  the  bile  in  the  duodenum.  In  the 
stomach  the  presence  of  bile  must  be  injurious. 

150.  Secretion  of  Bile. — The  secretion  of  bile  goes  on 
constantly,  but  is  more  rapid  at  one  time  than  another.  It  is 
accelerated  after  taking  food,  usually  attaining  its  maxjmum 
from  two  to  four  hours  after  each  meal.  The  secretion  is 
observed  by  tying  the  gall  duct  and  introducing  a  canula  into 
the  gall  bladder.  A  detailed  account  of  the  method  of  perform- 
ing this  operation  on  dogs  is  given  by  Rutherford  and  Gamgee  in 
the  report  of  the  British  Association  for  1868.  The  principal 
facts  may  be  demonstrated  in  the  guineapig,  as  follows : — 


BY   DR.    LAUDER   BRUNTON.  505 

**  151.  Mode  of  Producing  Biliary  Fistula  in 
Guineapigs. — Chloroform  the  animal  and  secure  it  on  the 
rabbit-support.  Make  an  incision  from  an  inch  to  an  inch  and 
a  quarter  long  through  the  abdominal  parietes  in  the  linea 
alba  from  the  xiphoid  process  downwards.  The  pyloric  end  of 
the  stomach  is  thus  exposed.  Pull  gently  on  the  stomach 
until  the  duodenum  is  brought  into  view.  The  part  correspond- 
ing to  the  superior  transverse  part  in  man  forms  a  loop  with 
its  convexity  directed  towards  the  diaphragm,  into  the  top  of 
which  convexity  the  ductus  choledochus  enters.  Tie  the  duct  in 
this  situation,  then  seize  the  gall  bladder  with  a  pair  of  forceps. 
It  is  always  full,  and  cannot  be  missed  if  the  forceps  are  passed 
immediately  under  the  edge  of  the  costal  cartilages.  Make  a 
small  incision  into  the  gall  bladder,  introduce  a  canula  and  tie 
it  in.  The  diameter  of  the  canula  should  be  from  two  to  three 
centimetres,  and  the  end  to  be  inserted  should  have  a  project- 
ing rim.  This  can  be  made  very  readily  by  heating  the  end  of 
a  piece  of  glass  tubing  of  the  proper  size,  and  pressing  it,  while 
hot,  against  a  flat  piece  of  iron.  Sew  up  the  wound,  leaving 
the  free  end  of  the  canula  outside.  The  bile  in  guineapigs  is 
secreted  in  very  large  quantities,  being  as  much  as  7.3  grammes 
in  an  hour  per  kilogramme  of  body  weight.  It  contains  a  very 
small  proportion  of  solids,  about  1.3  per  cent.  When  the  bile 
duct  is  tied  the  guineapigs  die  in  less  than  twentj'-four  hours, 
but  when  it  is  not  tied  they  will  live  for  a  week.  The  bile  is  se- 
creted under  a  very  low  pressure.  For  estimating  this  pressure, 
prepare  a  manometer  by  attaching  a  piece  of  glass  tubing, 
eighteen  inches  long,  to  a  wooden  or  pasteboard  scale.  Fit  an 
India-rubber  tube  to  its  lower  end,  fill  the  manometer  and  tube 
with  water,  and  close  the  latter  with  a  clip.  Tie  the  ductus 
choledochus  of  a  guineapig,  and  secure  a  canula  in  its  gall 
bladder.  Having  ascertained  that  the  water  in  the  manometer 
stands  at  about  100  millimetres  above  the  zero  point,  place  the 
tube  in  a  horizontal  position  at  the  same  level  as  the  canula. 
Connect  the  India-rubber  tubing  with  the  canula,  and  remove 
the  clip.  As  the  bile  is  secreted,  the  column  of  water  advances, 
and  the  rapidity  of  secretion  is  thus  indicated.  When  it 
reaches  150  millimetres  on  the  scale,  raise  the  tube  to  a  vertical 
position.  If  the  maximum  pressure  under  which  secretion 
occurs  in  the  animal  experimented  on  be  used,  the  water  will 
descend  in  the  tube,  but  if  not,  it  will  continue  to  rise. 

**  152.  Absorption  by  the  Liver. — The  bile  which  has 
been  secreted  by  the  liver  is  re-absorbed  either  when  the  pres- 
sure is  diminished  in  the  bloodvessels,  or  when  it  is  increased 
in  the  bile  capillaries  (Heidenhain) ;  jaundice  may  thus  be  pro- 
duced in  two  ways.  To  show  absorption  from  diminished 
pressure  in  the  bloodvessels,  compress  the  aorta  just  under- 
neath the  diaphragm.     The  pressure  in  the  manometer  some- 


506  DIGESTION. 

times  falls,  but  as  the  vena  cava  and  other  parts  are  generally 
compressed  likewise,  the  result  is  not  constant.  To  show  ab- 
sorption from  increased  pressure  in  the  ducts,  replace  the  water 
in  the  manometer  by  aqueous  solution  of  indigo-carmine,  taking 
care  that  the  column  of  fluid  stands  several  inches  above  the 
highest  level  previously  attained  by  it.  The  solution  is  gradu- 
ally absorbed,  muscular  tremors  occur,  and  the  animal  dies 
just  as  if  water  had  been  injected  into  the  veins.  At  the  same 
time  the  surface  becomes  colored  blue  by  the  indigo-carmine. 
The  experiment  enables  us  to  understand  how  a  very  slight 
obstruction  to  the  orifice  of  the  bile  duct  is  sufficient  to  deter- 
mine re-absorption,  and  the  production  of  jaundice. 

GLYCOGEN. 

153.  It  would  form  a  marked  exception  to  the  economical 
use  of  material  which  we  find  in  the  body  if  the  liver,  the 
largest  gland  in  it,  had  as  its  sole  function  the  secretion  of 
bile;  a  fluid  of  much  less  importance  in  digestion  than  the 
gastric  or  pancreatic  juices.  This,  however,  is  not  the  case, 
for,  in  addition  to  secreting  bile,  the  liver  has  the  power  of 
forming  glycogen,  a  substance  which  resembles  dextrin  in  its 
reactions,  and  like  it,  can  be  converted  into  sugar  by  the  action 
of  ferments.  It  is  always  present  in  the  liver  in  larger  amount 
during  digestion  than  during  fasting.  What  the  materials 
from  which  it  is  formed  actually  are  is  uncertain.  Its  amount 
is  increased  by  the  use  of  starchy  food ;  but  as  it  continues  to 
be  formed  in  considerable  quantity  when  the  food  consists  of 
flesh  alone,  it  is  evident  that  it  can  be  produced  from  albumin- 
ous bodies.  In  support  of  its  origin  from  albumin,  it  has 
been  argued  that  the  increased  amount  which  is  met  with  after 
the  administration  of  starchy  food,  is  due  to  the  sugar  derived 
from  the  starch  being  burnt  off  instead  of  albumin,  in  con- 
sequence of  which  more  albumin  remains  to  be  converted  into 
glycogen.  The  experiments  of  Cyon  (if  the}7  are  to  be  relied 
upon)  make  it  probable  that  urea  is  formed  in  the  liver.  As 
the  amounts  of  sugar  and  urea  excreted  by  diabetic  patients 
fed  on  an  animal  diet,  run  parallel  with  one  another,  it  might 
be  supposed  that  when  the  diet  is  exclusively  albuminous, 
glycogen  is  formed  by  albumin  or  peptones  splitting  up  and 
yielding  glycogen  and  urea.  Again,  when  the  diet  consists  of 
starch  and  sugar,  glycogen  is  formed  abundantly,  and  at  the 
same  time  a  deposit  of  fat  takes  place  in  the  liver.  From  this 
it  might  be  supposed  that  the  sugar  absorbed  from  the  intes- 
tine is  decomposed  so  as  to  yield  glycogen  and  fat.  Glycogen 
seems  to  be  of  great  importance  for  cell  growth,  for  it  is  found 
wherever  this  is  going  on  actively,  as  in  new  formations,  or  in 
embryonic  tissues.    A  remarkable  experiment  of  Hoppe-Seyler 


BY    DR.    LAUDER    BRUNTON.  507 

shows  that  it  is  an  ingredient  of  colorless  blood  corpuscles  so 
long  as  they  are  active,  but  that  when  they  lose  their  power  of 
motion  their  glycogen  disappears,  and  is  replaced  by  sugar.1 
In  early  foetal  life,  the  muscular  fibres  and  lungs  contain  much 
glycogen,  which  subsequently  diminishes.  The  liver  and  other 
glands,  and  the  nervous  system  of  the  embryo,  contain  little 
or  no  glycogen  ;  but  it  is  found  in  large  quantities  in  the  pla- 
centa. After  birth  it  is  confined  almost  entirely  to  the  liver 
and  muscles.  In  the  latter  it  seems  to  have  some  relation  to 
the  work  done  b}r  them,  for  the  quantity  present  in  them  is 
diminished  by  activity.  The  glycogen  of  the  liver  does  not 
remain  in  it  long,  but  is  soon  converted  into  sugar,  so  that  the 
large  quantity  which  is  present  after  a  meal  is  quickly  dimin- 
ished by  fasting,  and  disappears  altogether  during  starvation, 
while  that  present  in  the  muscles  does  not  increase  so  much 
after  food,  nor  is  it  so  quickly  lessened  by  starvation  (Weiss). 
Although  both  the  liver  itself  and  the  blood  contain  a  fer- 
ment which  transforms  glj'cogen  into  sugar,  its  conversion  is 
probably  effected  in  great  measure  by  the  blood,  for  it  takes 
place  more  rapidly  when  the  circulation  through  the  liver  is 
quickened.  It  is  uncertain  what  the  use  of  the  sugar  in  the 
organism  is,  but  possibly  it,  as  well  as  glycogen,  has  some- 
thing to  do  with  muscular  action,  since  the  quantity  of  sugar 
(or  a  substance  reducing  copper)  in  blood  becomes  much  dimin- 
ished in  its  passage  through  the  vessels  of  contracting  mus- 
cles (Genersich).  While  Bernard  considers  that  the  formation 
of  sugar  goes  on  in  the  liver  constantly  during  life,  this  has 
been  denied  by  Pavy,  Ritter,  Meissner,  and  Schiff,  who  hold 
that  it  only  occurs  after  death,  or  under  pathological  condi- 
tions, such  as  disturbance  of  the  respiration  or  circulation 
during  life.  They  base  their  opinions  on  the  observations  that 
the  liver  contains  little  or  no  sugar  when  examined  imme- 
diately after  death,  and  that  the  blood  of  the  hepatic  vein  does 
not  contain  more  sugar  than  that  of  the  portal  or  jugular  veins. 
It  is  quite  true  that  sugar  is  found  only  in  very  small  amount 
in  fresh  livers ;  but  the  smallness  of  the  quantity  is  in  all  pro- 
bability due  to  the  constant  circulation  through  the  liver 
during  life,  washing  the  sugar  out  of  it  as  soon  as  it  is  formed 
(Flint).  The  statement  that  the  blood  of  the  portal  contains 
as  much  sugar  as  that  of  the  hepatic  vein,  rests  on  experiments 
vitiated  by  the  omission  to  place  a  ligature  on  the  former  while 
removing  the  liver,  so  that  the  hepatic  vein  having  no  valves, 
the  blo«d  from  it  flowed  back  into  the  portal  S3rstem.  When 
this  fallacy  is  avoided,  sugar  is  found  in  much  larger  propor- 
tion in  the  hepatic  than  in  the  portal  vein.    To  meet  the  objec- 

1  For  the  details  of  this  experiment  see  Med.  Chem.  Untersuch.,  1871, 
p.  480. 


508  DIGESTION. 

tion  that  BUgai  thus  found  has  been  formed  after  death,  blood 
has  been  taken  from  the  right  side  of  the  heart,  or  vena  cava, 
and  the  quantity  of  sugar  it  contained  compared  with  a  similar 
specimen  of  blood  from  the  jugular  vein.  Every  precaution 
was  taken  to  avoid  disturbance  of  the  circulation,  yet  the 
sugar  in  the  former  was  found  to  exceed  that  in  the  latter  con- 
siderably  (Lusk). 

**  154.  Mode  of  demonstrating  the  Glycogenic 
Function  of  the  Liver. —  The  Liver  contain*  Sugar  which 
can  be  removed  by  Washing. — Kill  a  large  rabbit  in  full  diges- 
tion, by  decapitation  with  a  long  knife.  Open  the  abdomen, 
remove  the  liver,  and  place  it  in  a  large  flat  dish,  such  as  is 
used  for  photographic  purposes.  Tie  a  canula  into  the  portal 
vein,  and  another  into  the  hepatic  vein.  Pass  a  stream  of 
water  through  the  portal  vein.  This  may  be  effected  by  a 
syringe ;  but  a  more  convenient  method  is  to  connect  the 
canula  in  the  portal  vein  by  means  of  India-rubber  tubing  with 
a  pressure-bottle  containing  water.  (See  page  1 14.)  Proceed 
in  every  respect  as  in  injecting  the  liver  for  anatomical  pur- 
poses, using  a  pressure  of  two  or  three  feet  of  water.  The 
liquid  which  flows  from  the  hepatic  vein  as  the  water  enters 
the  portal  vein,  will  be  at  first  blood,  then  blood  diluted  with 
water,  and,  lastl}',  pure  water.  Collect  portions  of  each  of 
these  fluids  in  small  beakers  as  they  flow  out.  The  remainder 
which  is  not  collected  is  allowed  to  run  into  the  dish  in  which 
the  liver  lies.  Test  each  of  the  fluids  for  grape  sugar.  It  will 
be  found  in  the  portions  first  collected,  the  quantity  gradually 
diminishing  as  the  washing  is  continued.  Eventually  it  disap- 
pears. Allow  the  stream  to  flow  until  none  can  be  detected  by 
any  of  the  tests  described  in  the  next  paragraph. 

As  soon  as  this  is  the  case,  disconnect  the  canula  without 
loss  of  time,  and  cut  the  liver  into  three  pieces.  Mince  one  of 
them  as  rapidly  as  possible,  put  it  immediately  into  water  boil- 
ing briskly,  and  acidulate  it  very  slightly  with  acetic  acid,  to 
coagulate  the  albumin.  Put  another  into  strong  alcohol  for  a 
minute  or  two,  pour  off  the  alcohol,  and  squeeze  the  remainder 
of  it  from  the  liver.  Then  cut  it  up  small,  cover  it  with  abso- 
lute alcohol  and  let  it  stand.  Allow  the  third  piece  of  liver  to 
lie  on  the  table.  After  the  liver  has  been  boiled  for  a  few  min- 
utes filter  the  water  from  it.  The  filtrate  is  milky.  Test  it  for 
sugar.  If  the  operation  has  been  rapidly  performed,  little  or 
none  will  be  found,  showing  that  all  the  sugar  has  been  re- 
moved from  the  liver. 

Sugar  is  again  formed  in  the  Liver  after  its  removal  by 
Washing. — After  the  third  piece  of  liver  lias  lain  on  the  table 
for  some  time,  cut  it  up  and  boil  it  like  the  first ;  filter,  and  test 
for  sugar ;  in  most  cases  it  will  be  found.     As  there  was  none 


BY    DR.    LAUDER    BRUNTON.  509 

in  the  other  piece,  this  sugar  must  have  been  formed  after  the 
liver  was  cut  in  pieces. 

The  Liver  contains  Glycogen,  a  Substance  whieh  can  be 
changed  into  Grape  Sugar  by  the  action  of  Ferments. — Take 
a  little  of  the  milky  filtrate  obtained  by  boiling  the  liver  which 
has  been  already  found  to  contain  no  sugar.  Add  to  it  a  little 
saliva,  and  let  it  stand  in  the  water-bath  at  35°  C.  for  a  few 
minutes,  or  warm  it  gently  over  a  spirit-lamp.  Then  add  liquor 
potassas  and  cupric  sulphate,  and  boil ;  sugar  is  found.  Evapo- 
rate the  milky  remainder  of  the  filtrate  to  a  small  bulk,  and 
add  alcohol  in  excess.  A  white  flocculent  precipitate  of  gly- 
cogen is  formed. 

The  Liver  also  contains  a  Diastatic  Ferment. — From  the 
other  piece  of  liver  which  has  been  placed  in  alcohol  prepare  a 
glycerin  solution,  as  directed  in  §  160.  Add  some  of  this  to  a 
solution  of  glycogen,  let  it  remain  in  the  water-bath  at  40°  C, 
and  test  small  portions  of  it  from  time  to  time.  Sugar  will  at 
length  be  found,  but  very  many  hours  may  be  necessary. 

155.  Mode  of  Testing  for  Sugar  in  Blood. — As  the 
albumin  and  coloring  matter  of  the  blood  would  interfere  with 
the  reaction,  they  must  be  removed  before  the  test  is  applied. 
Bernard's  method  is  as  follows:  Put  the  blood,  if  pure,  in  a 
mortar,  and  rub  it  up  with  a  quantity  of  animal  charcoal,  suffi- 
cient to  form  a  dry  paste.  Add  a  little  water,  rub  it  up  again, 
and  throw  the  mixture  on  a  filter.  The  water  filters  through 
quite  clear,  holding  in  solution  any  sugar  which  may  be  pre- 
sent, and  Trommer's  test  may  then  be  applied  to  it.  If  the 
blood  is  diluted,  agitate  it  well  with  sufficient  animal  charcoal 
to  form  a  thick  paste ;  filter  it,  and  test  as  before. 

Another  method,  which  is  preferable  if  the  quantity  of  sugar 
is  to  be  estimated,  is  to  mix  the  blood  with  three  or  four  times 
its  bulk  of  strong  spirit,  and  after  allowing  it  to  stand  for  some 
time,  to  filter.  The  residue  is  then  extracted  with  much  alco- 
hol, and  after  the  addition  of  the  extract  to  the  filtrate,  the 
alcohol  is  evaporated  off  and  the  residual  liquid  tested.  Trom- 
mer's test  answers  for  saliva,  but  in  the  present  case  it  is  inade- 
quate, as  many  other  substances  capable  of  reducing  cupric 
oxide  might  be  present.     Other  tests  are  therefore  required. 

Moore's  Test. — Put  the  solution  in  a  test-tube  and  add  suffi- 
cient liquor  potassoe  or  liquor  sodae  to  make  it  strongly  alka- 
line. Heat  it  gently  to  boiling.  If  sugar  is  present  in  con- 
siderable quantit}r,  the  fluid  will  become  first  yellow,  then 
reddish-brown,  and,  lastly,  dark  brown  or  black  ;  but  if  there 
is  only  a  little  sugar,  the  color  will  only  become  yellow  or  red- 
dish-brown. 

Bottehers's  Test. — Put  the  solution  in  a  test-tube,  and  add  to 
it  as  much  bismuth  oxide  or  subnitrate  as  will  lie,  on  the  point 
of  a  knife,  and  a  considerable  excess  of  a  very  strong  solution 


510  DIGESTION. 

of  caustic  potash  or  soda,  and  boil  for  some  time.  If  sugar  is 
present,  the  bismuth  oxide  will  be  reduced  and  become  at  first 
gray,  and  lastly  black.  If  only  traces  of  sugar  are  present,  a 
small  quantit}'  of  bismuth  must  lie  used,  or  the  whole  will  not 
be  reduced;  if  a  first  trial  gives  only  a  gray  color,  it  should 
be  repeated  with  a  smaller  quantity  of  bismuth. 

Fermentation  Test. — A  solution  of  grape  sugar  mixed  with 
yeast  should  at  once  ferment  and  give  oil"  carbonic  acid.  A 
convenient  apparatus  for  testing  this  is  described  by  Bernard. 
It  consists  of  a  test-tube,  about  three  inches  long,  fitted  with  a 
tight  cork,  through  which  a  piece  of  small  glass  tubing  passes 
to  the  bottom.  The  tube  is  to  be  completely  filled  with  the 
fluid  to  be  tested,  mixed  with  a  little  yeast,  and  then  put  in 
the  water-bath  at  35°  C.  If  sugar  is  present,  carbonic  acid  is 
given  off,  and  as  it  cannot  escape,  it  drives  the  fluid  out  through 
the  small  tube.  As  the  yeast  may  contain  sugar  itself,  a  similar 
tube  should  be  filled  with  yeast  and  water  for  comparison  with 
the  first.  The  gas  may  be  shown  to  be  carbonic  acid  by  shak- 
ing it  with  baryta  water.  The  fluid  which  escapes  should  be 
collected  by  means  of  a  piece  of  India-rubber  tubing  attached 
to  the  upper  end  of  the  small  tube,  and  tested  for  alcohol  by 
boiling  it  with  a  little  potassium  bichromate  and  sulphuric  acid. 
If  alcohol  is  present  the  fluid  becomes  green. 

**  156.  Preparation  of  Glycogen. — In  order  to  obtain  a 
large  amount  of  glycogen  from  a  liver,  the  animal  must  be 
healthy,  and  must  be  killed  during  digestion,  as  otherwise  the 
liver  would  contain  but  little  glycogen.  Conversion  into  sugar 
after  death  must  be  prevented  by  rendering  the  ferment  which 
acts  on  it  inactive,  as  quickly  as  possible  ;  this  is  done  by  heat- 
ing the  liver  to  100°  C. 

Kill  a  large  and  well-fed  rabbit  an  hour  or  two  after  it  has 
had  a  full  meal,  by  decapitation  with  a  long  knife.  Open  the 
abdomen  instantly,  tear  out  the  liver,  chop  it  into  pieces  as 
quickly  as  possible  with  a  few  strokes  of  the  knife,  and  throw 
it  into  a  capacious  capsule  containing  water,  which  is  kept 
briskly  boiling  by  a  large  Bunsen's  burner.  The  burner  must 
be  large,  because  the  liver  cools  the  water  into  which  it  is 
thrown,  and  unless  ebullition  be  kept  up  briskly  it  may  be  some 
time  before  the  pieces  of  liver  are  heated  to  100u  C.  throughout, 
in  which  case  the  transformation  of  glycogen  into  sugar  will 
go  on  in  those  parts  which  are  insufficiently  heated.  Let  the 
liver  boil  briskly  for  a  short  time  ;  then  pour  the  liquid  out  of 
the  capsule  into  a  large  beaker,  and  put  the  liver  into  a  mortar. 
Return  the  liquid  to  the  capsule,  rub  the  liver  to  a  fine  pulp, 
put  it  back  into  the  capsule  and  boil  it  again.  Then  filter  the 
liquid  and  cool  the  filtrate  rapidty,  by  placing  the  vessel  con- 
taining it  in  iced  water.  The  filtrate  contains  a  considerable 
quantity  of  albuminous  substances,  which  must  be  removed  in 


BY    DR.    LAUDER    BRUNTON.  511 

order  to  get  the  gtycogen  pure.  This  is  best  done  by  precipi- 
tating them  with  potassio-mercuric  iodide,  as  recommended  by 
Briicke.  This  solution  is  made  by  precipitating  a  solution  of 
mercuric  chloride  with  potassium  iodide,  washing  the  precipi- 
tate and  adding  it  to  a  boiling  solution  of  potassium  iodide  till 
the  latter  is  saturated. 

When  the  filtrate  from  the  liver  is  cool,  add  hydrochloric  acid 
and  potassio-mercuric  iodide  solution  to  it  alternately,  as  long 
as  they  cause  any  precipitate.  Stir  the  mixture,  let  it  stand 
about  five  minutes,  and  then  filter.  Add  alcohol  to  the  filtrate 
till  glycogen  begins  to  be  copiousl}'  precipitated,  taking  care 
not  to  add  an  excess  of  alcohol,  lest  other  substances  be  also 
precipitated.  The  glycogen  is  best  precipitated  when  the  mix- 
ture contains  60  per  cent,  of  absolute  alcohol.  Collect  the  gly- 
cogen in  a  filter,  wash  it,  first  with  dilute  alcohol,  then  with 
strong  alcohol  of  90  per  cent.  (sp.  gr.  822),  which  makes  it  more 
easy  to  separate  from  the  filter.  Extract  it  with  ether  and  dry 
it  rapidly  on  a  flat  plate.  Instead  of  separating  the  albumin 
from  the  glycogen  by  potassio-mercuric  iodide,  the  boiling  solu- 
tion of  glycogen  may  be  slightly  acidulated  with  acetic  acid 
and  filtered.  The  filtrate  is  then  quickly  evaporated  to  half  its 
bulk  and  mixed  with  its  own  volume  of  strong  alcohol  of  90 
per  cent.  The  glycogen  is  precipitated  along  with  a  little  glu- 
tin.  To  separate  it  from  this  it  is  boiled  with  liquor  potass* 
for  an  hour  or  more,  neutralized  with  acetic  acid,  precipitated 
with  alcohol,  collected  on  a  filter,  washed  first  with  strong  alco- 
hol and  then  with  absolute  alcohol  till  all  traces  of  water  have 
been  removed,  and  then  the  alcohol  displaced  by  absolute  ether. 
The  glycogen  remains  as  a  white  powder.  It  is  to  be  quickly 
dried  by  spreading  it  in  a  thin  layer  on  a  warm  porcelain  plate 
and  passing  a  current  of  air  over  it.  If  the  glutin  has  not  been 
perfectly  removed,  or  if  the  water  has  been  incompletely  dis- 
placed by  the  alcohol  and  ether,  the  glycogen  in  drying  becomes 
converted  into  a  gummy  mass,  instead  of  forming,  as  it  ought 
to  do,  a  white  powder. 

*  157.  Properties  of  Glycogen. — Glycogen  is  amorphous, 
colorless,  and  tasteless.  In  water  it  is  readily  soluble.  The 
solutions  are  strongly  opalescent,  and  when  concentrated  are 
quite  milky.  They  are,  apparently,  true  solutions,  as  the}7  pass 
unchanged  through  filters  and  through  animal  charcoal,  and  no 
particles  can  be  observed  in  them  by  the  microscope.  Briicke, 
however,  considers  that  they  are  not  true  solutions,  but  merely 
suspensions  of  particles  of  glycogen  swollen  up  in  the  fluid.  The 
opalescence  disappears  on  the  addition  of  caustic  alkalies, 
although  the  alkali  does  not  destroy  the  glycogen.  In  alcohol 
and  in  ether  it  is  insoluble.  It  contains  no  nitrogen.  When 
burnt  on  platinum  foil,  it  does  not  give  off  the  peculiar  smell 
of  nitrogenous  bodies,  nor  does  it  leave  any  ash. 


512  DIGESTION. 

Glycogen  is  colored  red  by  solution  of  iodine.  The  best 
solution  for  this  purpose  is  made  by  putting  a  little  iodine  in 
water  and  adding  potassium  iodide  very  gradually  to  it,  with 
constant  agitation,  until  the  fluid  assumes  a  wine-red  color.  If 
caustic  potash  is  added  to  a  solution  of  glycogen,  and  then  a 
drop  of  cupric  sulphate,  the  copper  oxide  is  redissolved.  The 
oxide  is  not  reduced  on  boiling. 

158.  Influence  of  Food  on  the  Amount  of  Glycogen 
in  the  Liver. — If  two  rabbits,  one  of  which  is  fed  abandantly 
with  corn,  the  other  sparinglj'  with  green  food,  are  kept  other- 
wise in  the  same  conditions  and  killed  at  the  same  period  of 
digestion,  it  is  found  that  the  liver  of  the  former  contains  much 
more  gtycogen  than  that  of  the  latter. 

**  159.  Conditions  "which  determine  the  Conver- 
sion of  Glycogen  into  Grape  Sugar. — Glycogen  can  be 
changed  into  dextrin  and  grape  sugar: — 

1.  By  Ferments. — Take  a  watery  solution  of  glycogen  and 
mix  some  saliva  with  it.  Put  the  mixture  into  two  test-tubes 
and  place  them  in  the  water-bath  at  37°  to  40°  C.  Take  out 
one  immediately  after  the  milkiness  of  the  solution  has  dis- 
appeared. Add  alcohol  to  it:  a  precipitate  of  dextrin  is 
formed.  Filter,  and  wash  the  precipitate  with  alcohol.  Put 
the  precipitate  in  water  :  it  becomes  transparent  and  dissolves, 
forming  a  solution  perfectly  free  from  opalescence.  Test  a 
little  of  the  solution  with  liquor  potassaa  and  cupric  sulphate  ; 
no  reduction  takes  place  on  boiling.  To  another  portion  add 
iodine  solution  ;  a  red  color  like  that  of  glycogen  appears. 
Test  the  alcoholic  filtrate  with  liquor  potassae  and  cupric  sul- 
phate:  it  is  reduced.  This  shows  that  the  glycogen  has  been 
converted  partly  into  dextrin  and  partly  into  grape-sugar  by 
the  salivary  ferment.  Let  the  other  test-tube  stand  for  some 
time  in  the  water-bath.  Add  alcohol.  If  it  has  stood  long 
enough,  no  precipitate  is  produced.  Test  it.  On  applying 
Trommer's  test  a  great  reduction  of  cupric  oxide  will  occur. 
This  shows  that  the  glycogen  has  been  entireh*  converted  into 
sugar  by  the  prolonged  action  of  the  salivary  ferment. 

Blood  contains  a  Ferment  which  converts  Glycogen. — A 
ferment  possessing  the  same  action  is  contained  in  the  blood. 
Add  a  little  blood  to  a  solution  of  glycogen,  and  let  it  stand 
for  some  time  at  37°  C.  Then  remove  the  albumin  and  test 
for  sugar  in  the  manner  ahead}' described. 

2.  By  Acids. — Mix  a  solution  of  glycogen  with  dilute  hydro- 
chloric or  sulphuric  acid  and  boil.  Then  add  liquor  potassae 
in  excess  and  copper  sulphate,  and  boil  ;  sugar  is  found.  All 
specimens  of  glycogen  can  be  converted  into  sugar  by  acids, 
but  they  are  not  all  alike  in  their  behavior  to  ferments,  some 
specimens  requiring  a  longer  time  than  others. 


BY    DR.    LAUDER    BRUNTON.  513 

160.  Separation  of  a  Diastatic  Ferment  from  the 
Liver. — Cut  off  the  head  of  a  rabbit  and  remove  the  liver  as 
quickly  as  possible.  Mince  it  and  wash  it  with  water  several 
times  to  remove  the  blood.  Then  squeeze  it  tolerably  dry,  put 
it  into  absolute  alcohol,  and  let  it  remain  for  twenty-four 
hours.  Filter  off  the  alcohol,  wash  the  liver  with  alcohol,  and 
then  put  the  mass,  for  several  days,  in  glycerin.  Filter  it 
through  muslin.  The  filtrate  is  free  from  sugar,  but  contains 
a  ferment  which  converts  glycogen  and  starch  into  sugar. 
Take  a  little  of  the  glycerin  extract  in  each  of  three  test- 
tubes  ;  put  into  one  a  little  glycogen,  and  into  another  a  little 
starch  paste,  and  let  them  stand  for  a  quarter  or  half  an  hour. 
Then  test  all  three  for  sugar  with  copper  sulphate  and  potash. 
No  sugar  will  be  found  in  the  tube  containing  the  glycerin 
extract  alone,  the  sugar  found  in  the  liver  immediately  after 
death  having  been  removed  by  the  alcohol  before  the  glycerin 
was  added.  Both  the  other  tubes  will  contain  sugar.  Diluting 
the  glycerin  extract  does  not  alter  the  effect. 

After  the  Ferment  has  been  extracted  by  Glycerin,  the  Mass 
still  contains  Glycogen. — Extract  the  mass  several  times  with 
fresh  glycerin.  Take  two  test-tubes  :  then  introduce  a  little  of 
it.  with  water  in  each,  and  let  them  into  two  test-tubes.  Test 
one  of  them  for  sugar :  none  is  found.  Add  to  the  other  one 
a  little  of  the  glycerin  extract,  which  has  already  been  found 
to  contain  no  sugar,  and  let  it  stand  at  40°  C.  for  some  time, 
after  which  it  will  be  found  to  contain  sugar.  A  similar 
ferment  can  be  extracted  from  bile  by  precipitating  it  with 
alcohol,  washing  the  precipitate  with  alcohol  on  a  filter,  and 
then  extracting  it  with  glycerin  in  the  way  already  mentioned 
(Von  Wittich). 

161.  Glycosuria. — It  is  still  disputed  whether  sugar  is  a 
normal  constituent  of  the  urine  or  not.  But  in  the  diseased 
condition,  to  which  the  term  Diabetes  Mellitus  is  applied,  it 
appears  in  considerable  quantities.  Bernard  first  showed  that 
its  appearance  in  the  urine  can  be  induced  by  certain  lesions 
of  the  nervous  system,  and  finding  that  they  caused,  at  the 
same  time,  dilatation  of  the  vessels  of  the  liver,  he  attributed 
the  appearance  of  the  sugar  to  the  increased  circulation 
through  that  organ.  His  views  have  lately  been  confirmed; 
the  nervous  mechanism  by  which  the  vessels  become  dilated 
has  been  discovered  by  Cyon  and  Aladoff,  from  whose  re- 
searches it  appears  that  the  vasomotor  nerves  of  the  hepatic 
vessels  pass  from  the  vasomotor  centre  in  the  medulla  oblon- 
gata down  the  cervical  part  of  the  spinal  cord,  which  they 
leave  at  its  lower  end.  Thence  they  accompany  the  vertebral 
arteries  to  the  last  cervical  ganglion,  finding  their  way  by  the 
two  fibres,  which  pass  in  front  and  behind  the  subclavian 
artery  (forming  the  annulus  of  Vieussens)  to  the  first  dorsal 

33 


514  DIGESTION. 

ganglion.  Thence  the}'  proceed  in  the  gangliated  cord  of  the 
sj'mpathetic  and  the  splanchnic  nerves  to  the  liver.  When 
these  vasomotor  fibres  are  severed,  either  by  dividing  the 
fil ins  on  the  vertebral  artery  or  those  forming  the  annulus  of 
Yienssens,  or  by  extirpating  the  third  cervical  or  first  dorsal 
ganglion,  the  hepatic  vessels  dilate,  and  diabetes  occurs.  It 
is  of  great  importance  to  notice  that  section  of  the  sympa- 
thetic cord  or  the  splanchnic  nerves  does  not  produce  diabetes, 
although  the  vasomotor  nerves  of  the  liver  are  thus  divided. 
The  reason  of  this  probably  is  that  the  vasomotor  nerves  of 
the  intestine,  being  divided  at  the  same  time,  so  much  blood 
goes  to  the  intestinal  vessels  that  the  circulation  in  the  liver 
is  not  increased.  The  vessels  can  be  dilated  reflexly  by  irrita- 
ting the  central  ends  of  the  cut  vagi,  or  the  roots  of  the  vagus 
in  the  fourth  ventricle.  Section  of  the  splanchnics  or  sym- 
pathetic cord  prevents  the  occurrence  of  diabetes  when  the 
fourth  ventricle  is  afterwards  punctured,  but  does  not  remove 
it  when  already  present.  Diabetes  may  also  be  produced  by 
the  inhalation  of  carbonic  oxide  (  Schmiedeberg),  chloroform, 
or  nitrite  of  amjd,  or  by  the  injection  of  curare.  As  regards 
carbonic  oxide,  it  has  been  ascertained  that  the  action  is  not 
prevented  in  the  dog  by  section  of  both  splanchnics,  but  in 
rabbits  it  does  not  produce  diabetes  at  all  (Eckhard). 

Increased  proportion  of  sugar  in  the  blood  determines  glj'co- 
suria.  To  show  this,  expose  the  jugular  vein  in  a  healthy  rab- 
bit, having  first  weighed  it  and  ascertained  that  its  urine  is  free 
from  sugar.  Then  slowly  inject  5  to  10  per  cent,  solution  of 
grape  sugar  into  the  vein.  About  two  grammes  of  sugar  should 
be  used  for  eveiy  kilogramme  of  body  weight.  Sugar  is  found 
in  the  urine  shortly  after,  but  next  da}r  it  will  have  disappeared. 
It  has  been  found  that  if  the  amount  of  sugar  in  the  blood  does 
not  exceed  a  half  a  gramme  for  each  kilogramme  of  body  weight, 
it  may  not  appear  in  the  urine. 

**  162.  Production  of  Glycosuria  by  Puncture  of 
the  Floor  of  the  Fourth  Ventricle. — The  part  of  the 
fourth  ventricle  the  puncture  of  which  is  followed  by  the  most 
abundant  appearance  of  sugar  in  the  urine  is  limited  superiorly 
by  a  Hue  joining  the  origin  of  the  auditory  nerves,  and  inferi- 
orl}-  by  one  joining  the  origins  of  the  vagi ;  a  puncture  higher 
up,  or  to  either  side,  may,  however,  produce  more  or  less  glyco- 
suria. It  has  been  ascertained  by  Bernard  that  it  is  essential 
to  the  result,  that  the  olivary  fasciculi  should  be  injured,  and 
that  it  is  not  produced  by  injury  of  the  superficial,  i.  e.,  poste- 
rior sensory  layers.  The  instrument  used  for  puncturing  the 
ventricles  consists  of  a  small  steel  chisel  (.see  Fig.  315),  about 
four  millimetres  broad,  and  having  a  style  in  the  middle  which 
projects  about  two  millimetres  beyond  the  cutting  edge.  This 
chisel  is  pushed  on  through  the  occipital  bone  and  the  cere- 


BY    DR.   LAUDER   BRUNTON.  515 

bellum  until  its  further  progress  is  arrested  by  the  point  com- 
ing in  contact  with  the  basilar  process  of  the  occipital  bone. 
In  this  wa}r  the  edge  of  the  chisel  is  prevented  from  injuring 
the  anterior  motor  fibres  of  the  medulla,  and  thus  producing  a 
disturbance  of  the  motor  functions  which  would  complicate  the 
experiment. 

Mode  of  Operation. — Place  a  rabbit  in  the  prone  position  on 
Czermak's  rabbit-support,  and  fix  the  head  to  the  upright  at 
the  side.  Feel  for  the  occipital  protuberance,  and  make  an  in- 
cision over  it  about  half  an  inch  long.  Fix  the  point  of  the 
chisel  in  the  middle  line  of  the  skull  just  behind  the  protube- 
rance, and  bore  through  the  bone,  moving  the  handle  of  the 
instrument  from  side  to  side,  in  order  to  assist  its  passage,  but 
not  pressing  with  too  great  a  force.  When  the  skull  has  been 
penetrated,  push  the  chisel  downwards  and  forwards  through 
the  cerebellum  in  such  a  direction  as  to  cross  a  line  joining  the 
two  auditory  meatus  (see  Fig.  31fi)  until  it  is  stopped  by  the 
basilar  process,  and  then  gently  withdraw  it.  Remove  some 
of  the  urine  in  half  an  hour  or  an  hour  afterwards  (§  138),  and 
test  it  for  sugar. 

Section  IV.— Digestion  in  the  Intestines. 

PANCREATIC  JUICE. 

163.  Pancreatic  juice  may  be  obtained  either  by  a  temporary 
or  permanent  fistula.  It  is  usually  stated  that  the  secretions 
from  these  two  kinds  of  fistula  differ  much  from  each  other,  a 
normal  juice  being  obtained  only  from  a  temporary  fistula, 
while  that  yielded  by  a  permanent  one  is  watery  and  destitute 
of  some  of  the  properties  possessed  by  the  other.  Ludwigand 
Bernstein,  however,  have,  by  an  improved  method  of  making  a 
permanent  fistula,  succeeded  in  obtaining  a  normal  juice  from 
it  also. 

164.  Method  of  itiaking  a  Temporary  Fistula. — In 
the  dog  there  are  two  pancreatic  ducts,  one  of  which  opens  into 
the  duodenum  along  with  the  ductus  choledochus.  The  other 
duct,  which  is  larger,  and  enters  the  duodenum  about  two  cen- 
timetres below  the  one  first  mentioned,  is  exclusively  employed 
for  the  operation.  It  is  not  necessary  to  ligature  the  first. 
Bernard  prefers  for  the  purpose  large  dogs,  sheep  dogs  being 
best,  as  they  are  less  subject  to  peritonitis  than  others.  Five 
or  six  hours  before  the  operation,  the  animal  should  get  a  large 
meal  of  bread  and  meat.  The  operation,  which  must  be  per- 
formed as  quickly  as  possible,  consists  in  laying  the  dog  on  its 
left  side,  and  making  an  incision  five  centimetres  long  in  the 
right  hypochondrium  from  the  projecting  point  of  the  last  false 
rib  downwards,  parallel  with  the  linea  alba.  The  bleeding 
should  be  stopped  before  the  peritoneum  is  opened.     The  duo- 


516  DIGESTION. 

denum  lies  opposite  the  wound.  As  soon  as  it  is  exposed  it  is 
drawn  out,  and  the  pancreatic  duct  looked  for  about  two  centi- 
metres below  the  ductus  choledochus.  The  part  of  the  pancreas 
in  which  the  duct  lies  is  generally  closely  attached  to  the  duo- 
denum, and  somewhat  overlaps  it.  The  largest  and  lowest  of 
the  bundles  of  vessels  which  pass  from  the  duodenum  to  the 
pancreas,  lies  over  the  duct.  These  vessels  are  to  be  pushed 
aside,  and  a  thread  passed  under  the  duct,  which  is  recognized 
by  being  larger  and  paler  than  the  vessels.  Care  must  be  taken 
not  to  injure  the  vessels  and  cause  bleeding,  and  the  pancreas 
must  be  pulled  or  pressed  as  little  as  possible.  The  duct  is 
opened  with  scissors,  and  a  plain  silver  canula,  about  five  mil- 
limetres in  diameter,  and  10  or  12  centimetres  long,  pushed 
into  it  up  to  its  first  division,  which  is  generally  visible;  the 
ligature  is  then  tightened;  another  thread  is  passed  through 
the  serous  coat  of  the  duodenum,  and  the  canula  fixed  to  the 
intestine  by  it.  The  ends  of  these  threads,  and  the  end  of  the 
canula,  are  kept  outside  the  wound,  the  duodenum  returned 
to  the  abdominal  cavity,  and  the  wound  closed  by  first  sewing 
together  the  muscles,  and  then  the  skin.  A  small  India-rubber 
bag.  furnished  with  a  stopcock,  is  then  tied  to  the  outer  end  of 
the  canula.  emptied  of  air.  and  the  stopcock  closed.  The 
juice  then  collects  in  it,  and  is  drawn  off  by  the  stopcock  (see 
Fig.  317).  Generally,  it  flows  abundantly;  but  if  it  does  not. 
a  little  ether  should  be  injected  into  the  stomach  by  a  stomach- 
pump.  The  juice  may  be  collected  for  several  hours;  but 
after  the  expiration  of  twenty-four  hours,  the  character  of  the 
secretion  changes.  In  a  few  hours  more,  the  canula  and 
threads  should  be  gently  drawn  out.  The  wound  generally 
heals  quickly. 

165.  Method  of  making  a  Permanent  Fistula. — For 
permanent  fistulpe,  Ludwig  and  Bernstein  choose  small  dogs, 
as  in  them  the  duodenum  is  more  easily  reached  from  the  mid- 
dle line,  and  is  not  drawn  so  far  from  its  natural  position  by 
the  fistula  as  in  larger  animals.  The  dog  must  be  kept  fasting 
on  the  day  of  the  operation,  as  the  pancreatic  vessels  are  full 
during  digestion,  and  bleed  easil}-.  Narcotize  the  animal  by 
injecting  opium  into  the  tibial  vein,  and  open  the  abdomen  by 
an  incision  about  two  centimetres  long  in  the  linea  alba,  mid- 
waj'  between  the  ensiform  cartilage  and  the  umbilicus.  The 
duodenum  is  then  searched  for,  and  drawn  out  of  the  wound 
along  with  the  attached  pancreas,  and  a  thread  looped  round 
the  duct.  Instead  of  then  putting  in  a  canula,  a  piece  of  lead 
wire  is  inserted  into  the  duct,  so  that  one  end  of  it  passes  into 
the  intestine  and  the  other  into  the  gland  to  a  considerable  dis- 
tance. The  middle  part  of  it  is  twisted  together,  and  projects 
through  the  wound.  Owing  to  the  T  shape  thus  given  to  the 
wire,  it  cannot  either  slip  out  or  move  about  in  the  duct;  but 


BY    DR.    LAUDER   BRUNTON,  517 

wire  being  chosen  which  does  not  fill  it  up,  the  flow  of  the  juice 
is  not  hindered.  Three  threads  having  then  been  passed 
through  the  wall  of  the  duodenum  near  the  duct,  the  intestine 
and  omentum  are  replaced  in  the  abdomen,  and  the  duodenum 
fastened  by  the  threads  to  the  abdominal  wall.  The  wound  is 
then  sewed  up,  care  being  taken  that  the  twisted  part  of  the 
lead  wire  passes  through  the  wound.  Twenty-four  hours  after 
the  operation,  the  stitches  are  taken  out,  but  the  wire  left  in. 
In  two  or  three  days  afterwards  the  juice  can  be  collected.  For 
this  purpose,  the  animal  must  be  supported  by  two  straps,  which 
pass  under  its  belly,  and  are  attached  to  a  horizontal  bar  hung 
from  the  roof  by  a  cord  and  pulley.  The  dog  is  thus  suspended 
over  a  table  at  such  a  height  that  it  can  barely  touch  it  with 
its  toes,  in  which  position  it  remains  perfectly  still.  A  funnel 
is  then  attached  under  the  fistula,  and  the  juice  collected  in  a 
glass  below. 

The  normal  juice  obtained  from  a  temporary  fistula  is  a  col- 
orless transparent  tenacious  fluid,  with  a  strongly  alkaline  re- 
action. "When  cooled  under  0°  C,  a  coagulum  separates  from 
it.  The  j  nice  from  permanent  fistulas  is  more  watery,  and  yields 
no  coagulum  when  cooled.  In  the  former,  it  often  contains 
about  10  per  cent,  of  solids,  but  the  amount  may  be  as  low  as 
2  per  cent. ;  and  in  the  latter,  the  percentage  is  frequently  from 
2  to  5.  Their  amount  is  determined  in  the  manner  described 
in  §  74.  Pancreatic  juice  contains  an  albuminous  body,  an 
alkali-albuminate,  leucine,  t}Trosine,  fats,  soaps,  inorganic  salts, 
and  three  ferments.  One  of  these  converts  starch  into  sugar, 
another  splits  up  fats,  liberating  fatty  acids,  and  the  third  con- 
verts albuminous  bodies,  first  into  peptones,  and  then  into  leu- 
cine and  t}'rosine.  On  account  of  the  presence  of  this  third 
ferment,  the  reactions  of  the  juice,  after  it  has  been  allowed  to 
stand,  differ  from  those  which  it  presents  when  fresh,  the  albu- 
min of  the  fresh  juice  itself  being  digested  by  the  ferment  in 
it,  and  yielding  peptones,  leucine,  and  tyrosine.  When  fresh 
juice  is  heated  to  72°  C,  the  albumin  coagulates,  and  after  the 
coagulum  has  been  separated,  acetic  acid  precipitates  the  alkali- 
albuminate.  The  watery  extract  of  the  gland  may  be  used  for 
showing  man}-  of  the  properties  and  actions  of  pancreatic  juice, 
instead  of  the  juice  itself. 

**  166.  Artificial  Pancreatic  Juice. — For  this  purpose, 
the  pancreas  from  an  animal  killed  in  full  digestion  must  be  em- 
ployed. Take  the  pancreas  of  an  animal  which  has  been  killed 
about  six  hours  after  a  full  meal.  Wash  off  the  blood,  cut  it 
into  moderately  small  pieces,  pour  about  four  times  its  weight 
of  water  at  25°  C.  over  it,  and  let  it  stand  for  two  hours  in  the 
water  at  that  temperature,  above  which  it  must  not  be  allowed 
to  rise  more  than  four  or  five  degrees  at  most.  Filter  it  first 
through  linen,  and  then  through  paper.     The  filtrate  generally 


518  DIGESTION. 

has  an  acid  reaction  from  the  presence  of  fatty  acids,  liberated 
by  the  ferment  from  the  fats  in  the  pancreas,  and  is  opalescent 
from  the  presence  of  fat  in  a  state  of  emulsion.  Boil  a  little  of 
the  fluid  ;  a  precipitate  of  albumin  is  formed.  Filter,  and  neu- 
tralize by  acetic  acids,  and  a  further  precipitate  of  alkali-albu- 
minate  will  be  produced.  The  presence  of  leucine  and  tyrosine 
may  be  shown  by  removing  the  albumin  by  boiling  and  acidu- 
lating, and  then  separating  them  as  described  in  §  35.  To  show 
that  leucine  is  present  in  the  juice  as  secreted,  and  is  not  due 
to  changes  in  it  afterwards,  it  must  be  received  in  alcohol  as  it 
flows  from  the  fistula. 

*  167.  Glycerin  Solution  of  Pancreatic  Ferments. — 
After  cutting  up  the  pancreas,  as  in  the  previous  experiment, 
lay  it  for  a  day  or  two  in  absolute  alcohol,  and  after  express- 
ing the  alcohol  let  it  lie  several  days  in  glycerin,  then  filter. 

**  168.  Actions  of  Pancreatic  Juice. — It  emulsionizes 

Fat Shake  up  some  of  the  watery  extract  with  olive  oil,  an 

emulsion  is  formed.  This  is  due  to  the  albumin  it  contains, 
for  by  adding  liquor  potassae  to  the  mixture  so  as  to  dissolve 
the  albumin,  and  shaking,  the  drops  of  fat  may  be  made  to 
run  together  again. 

2.  It  decomposes  Fats,  liberating  Fatty  Acids. — The  extract 
of  pancreas  contains  fat :  hence  when  it  is  kept  for  an  hour  in 
the  water-bath  at  40°  C,  without  any  addition,  its  acid  reac- 
tion increases.  To  show  its  action  on  fats,  carefully  neutralize 
some  of  the  watery  extract  and  add  to  it  a  little  olive  oil  or 
fresh  butter,  whose  reaction  must  also  be  neutral.  Put  the 
mixture  in  the  water-bath  for  some  time,  put  a  drop  from  the 
bottom  of  the  tube  on  blue  litmus  paper  and  let  it  run  off.  A 
red  and  somewhat  greasy  spot  is  left. 

3.  //  converts  Starch  into  Sugar. — Mix  some  of  the  extract 
with  starch  mucilage  and  let  it  stay  for  some  minutes  in  the 
water-bath  at  40°  C. ;  then  apply  Trommer's  test,  and  sugar 
will  be  found. 

4.  It  digests  Fibrin,  forming  Peptones,  and  afterwards  de- 
composes them,  Leucine  and  Tyrosine  being  produced. — Before 
dissolving  boiled  fibrin,  the  pancreatic  juice  converts  it  into  a 
soluble  albuminous  substance,  very  much  like  raw  fibrin.  This 
is  then  dissolved  and  is  present  in  solution,  either  as  albumin, 
coagulable  by  heat,  or  as  an  albuminate.  The  dissolved  albu- 
min is  next  converted  into  peptones.  If  the  digestion  is 
allowed  to  go  on,  the  quantity  of  peptones  in  the  solution 
diminishes,  while  that  of  leucine  and  tyrosine  increases.  Bodies 
which  give  the  reaction  of  naphthilamine  and  indol  (Kiihne) 
are  also  formed,  and  when  the  digestion  goes  on  for  a  long 
time  the  indol  is  formed  in  considerable  quantities,  and  emits 
a  most  disagreeable  faecal  odor,  which  was  attributed  to  putre- 
faction till  Kiihne  showed  its  true  nature.    Boil  several  bits  of 


BY    DR.    LAUDER    BRUNTON.  519 

fibrin  in  a  large  test-tube,  pour  off  the  water,  add  artificial 
pancreatic  juice  or  glycerin  extract  of  pancreas,  and  put  the 
tube  in  the  water-bath  at  40°  C.  At  first  it  will  not  be  altered, 
but  after  two  hours  or  more  the  bits  will  be  found  to  be  easily 
torn  by  stirring,  and  the  smaller  ones  will  disappear,  and  if 
two  or  three  are  taken  out  and  washed  with  water  they  will 
be  seen  to  be  corroded,  not  swollen  as  in  gastric  juice.  To 
show  that  the  coagulated  fibrin  has  been  converted  by  the 
pancreatic  juice  into  a  body  resembling  raw  fibrin  in  its  pro- 
perties, put  a  bit  into  0.1  per  cent,  of  hydrochloric  acid.  It 
dissolves  veiy  cpiickly,  forming  a  solution  of  syntonin.  Rub 
up  a  second  bit  with  10  per  cent,  salt  solution,  and  filter.  The 
filtrate  contains  albumin  in  solution.  Add  nitric  acid  to  one 
portion  of  it  and  boil  another ;  a  precipitation  occurs  in  both. 
If  boiled  fibrin  is  tested  in  the  same  way,  it  is  found  to  be 
insoluble  in  these  reagents.  Even  raw  fibrin  is  much  less  solu- 
ble than  the  boiled  fibrin  which  has  been  acted  on  by  pancreatic 
juice. 

Take  part  of  the  solution  of  fibrin  in  pancreatic  juice  and 
boil  it.  Neutralize  another  portion  with  acetic  acid ;  a  precipi- 
tate is  formed  in  both.  Let  the  rest  stand  for  two  or  three 
hours  longer,  then  acidulate  it  with  acetic  acid  and  boil,  to 
coagulate  any  albumin  present.  Filter.  Evaporate  the  filtrate 
at  60°  to  70"  C,  and  add  alcohol  to  it  while  still  hot,  till  the 
peptones  are  precipitated.  Let  it  stand  for  twenty-four  hours 
and  filter.  Dissolve  the  precipitate  of  peptones  in  water  and 
apply  the  tests  given  in  §  118.  Evaporate  the  filtrate  to  a 
moderately  small  bulk  and  let  it  cool.  Tyrosine  crystallizes 
out.  Pour  off  the  mother  liquor,  evaporate  it  to  a  small  bulk, 
and  leucine  will  crystallize  out.  In  order  to  purify  the  tyro- 
sine, put  it  on  a  filter  and  wash  it,  first  with  ice-cold  water  till 
the  filtrate  is  colorless,  and  then  with  spirit,  next  with  abso- 
lute alcohol,  and  lastly  with  ether.  To  purify  the  leucine,  put 
the  crystals  on  a  filter,  which  must  be  allowed  to  stand  in  a 
cool  place  until  not  a  drop  more  runs  from  it.  Then  wash  it, 
first  with  ice-cold  water  until  the  filtrate  is  colorless,  next 
with  common  alcohol,  then  with  absolute  alcohol,  and  lastly 
with  ether.  It  is  of  great  importance  that  the  mother  liquor 
should  be  allowed  to  drain  away  completely  before  the  wash- 
ing, as  otherwise  the  crystals  would  dissolve  in  the  water  used. 
Test  the  mother  liquor  for  naphthilamine  and  indol.  In  test- 
ing for  the  former,  dilute  naphthilamine  is  indicated  by  the 
appearance  of  a  rose-red  color  when  chlorine  water  is  added 
gradually  to  the  mother  liquor  diluted  with  water.  To  prove 
the  presence  of  indol,  dilute  some  of  the  mother  liquor,  boil  it 
in  a  test-tube,  add  a  little  dilute  sulphuric  acid  and  a  drop  or 
two  of  a  dilute  solution  of  a  nitrite  ;  or  of  very  dilute  nitrous 
acid,  a  red  color  is  produced.    The  dilute  nitrous  acid  for  this 


520  DIGESTION. 

purpose  may  be  conveniently  obtained  by  boiling  a  small  piece 
of  grape  sugar  with  nitric  acid  in  a  test-tube,  and  when  the 
tube  is  filled  with  red  fumes  emptying  out  the  acid  and  filling 
the  test-tube  writh  water. 

*  169.  Separation  of  the  Pancreatic  Ferments  from 
the  Glycerin  Extract. — Precipitate  the  glycerin  extract  by 
absolute  alcohol;  filter;  treat  the  precipitate  again  for  a  week 
or  two  with  glycerin,  and  filter;  let  the  filtrate  fall  drop  by 
drop  into  a  tall  cylinder  filled  with  absolute  alcohol.  The 
ferment  is  precipitated  in  white  flocculi.  After  the  precipita- 
tion is  complete,  let  it  stand  one  or  two  days  under  a  mixture 
of  alcohol  and  ether.  Filter  by  means  of  Bunsen's  pump,  and 
wash  several  times  with  alcohol  and  ether.  Let  the  precipitate 
dry  over  sulphuric  acid,  and  then  pulverize  it  (Hiifner). 

170.  Isolation  of  the  Pancreatic  Ferments. — Two  of 
the  pancreatic  ferments  have  been  separated  by  Danilewsky  ; 
but  that  which  splits  up  fat  is  removed  or  destroyed  by  the 
magnesia  he  employs.  His  method  is  as  follows:  "Wash  the 
pancreas  of  a  dog  which  has  been  killed  six  hours  after  a  full 
meal  thoroughly  from  blood,  and  rub  it  to  a  fine  pulp  in  a 
mortar,  with  about  a  quarter  of  its  bulk  of  magnesia,  and 
four  times  its  bulk  of  water.  Put  the  mixture  in  a  beaker, 
and  let  it  stand  for  two  hours  at  25°  in  the  water-bath.  After 
it  has  cooled,  and  the  pulp  and  magnesia  have  nearly  subsided, 
filter  the  fluid,  but  do  not  put  the  sediment  on  the  filter,  as  it 
chokes  it,  and,  at  the  same  time,  partly  passes  through.  Neu- 
tralize the  filtrate  with  dilute  hydrochloric  acid,  and  put  it 
into  a  flask  large  enough  to  hold  three  times  as  much.  Pour 
into  it  without  stirring  ^-^  of  its  volume  of  thick  collodion, 
and  shake  it  sharply  for  several  minutes,  and  repeat  the  shaking 
several  times.  Pour  the  liquid  into  a  large  beaker,  and  stir 
it  constantly,  so  as  to  favor  the  escape  of  ether  and  prevent 
the  collodion  from  separating  in  large  lumps.  When  the  col- 
lodion presents  the  appearance  of  small  rounded  granules, 
filter  through  linen,  and  evaporate  the  ether  from  the  filtrate 
in  vacuo.  Then  treat  the  liquid  with  collodion  a  second  time, 
filter  through  the  same  piece  of  linen,  unite  both  filtrates,  and 
put  them  aside (a) 

Wash  the  precipitate  several  times  with  spirit  (60  to  10  per 
cent.),  and  dry  it  without  removing  it  from  the  linen  between 
double  folds  of  blotting  paper.  Spread  it  out  with  a  spatula, 
and  leave  it  exposed  to  the  air  till  it  is  dry.  Then  shake  it  in 
a  tall  narrow  glass  with  ether,  to  which  a  little  absolute  alcohol 
has  been  added,  till  the  precipitate  is  dissolved  and  a  turbid 
solution  obtained.  Let  it  stand  for  two  days,  and  then  decant 
the  turbid  fluid  from  the  precipitate,  and  after  diluting  it  witli 
ether,  pour  it  into  two  tall  glasses  and  let  it  stand  for  several 
days  till  a  new  precipitate  subsides.     Collect  that  which  then 


BY    DR.    LAUDER    BRUNTON.  521 

remains  suspended  by  filtration  through  Swedish  paper.  Re- 
move the  collodion  from  each  precipitate  by  agitating  it  with 
ether  several  times,  and  then  dry  it  in  vacuo.  Treat  the 
yellowish  residue  (which  consists  of  an  admixture  of  coagu- 
lated albumin  with  that  pancreatic  ferment  which  acts  on 
fibrin)  with  cold  water,  and  filter.  The  ferment  will  be  dis- 
solved and  the  albumin  left.  Test  the  digestive  power  of  the 
filtrate  on  a  bit  of  fibrin. 

Evaporate  the  filtrate  (a)  in  vacuo,  filter  from  the  collodion 
that  separates,  heat  to  43°-44°  C.  in  a  water-bath,  in  order  to 
separate  an  albuminous  body  contained  in  it  which  coagulates 
at  this  temperature.  Filter;  evaporate  the  filtrate  in  vacuo  to 
one-sixth  of  its  bulk,  and  add  a  large  quantity  of  absolute 
alcohol.  It  is  advisable  to  let  the  precipitate  thus  produced 
remain  under  the  alcohol  for  some  days,  as  it  is  thus  rendered 
more  insoluble  in  water.  Collect  the  precipitate  on  a  filter, 
and  wash  it  several  times  with  strong  spirit.  Then  treat  it 
with  a  mixture  of  one  part  of  strong  spirit  and  two  parts  water, 
in  order  to  dissolve  the  ferment  and  leave  the  albumin.  Filter  ; 
evaporate  the  filtrate  to  dryness  in  vacuo,  and  dissolve  the 
residue  in  water.  The  solution  converts  starch  quickly  into 
sugar,  and  digests  fibrin,  but  not  very  quickly,  the  ferment 
having  this  latter  action  not  having  been  completely  removed 
by  the  collodion.  It  contains  also  leucine  and  tyrosine,  but 
the  greater  part  of  these  may  be  removed  by  dialysis  at  4°  C. 
The  ferment  should  then  be  dried  in  order  to  keep  it. 

171.  Preparation  of  Tyrosine  by  Pancreatic  Diges- 
tion.— Take  out  the  pancreas  of  an  animal  which  has  been  fed 
five  or  six  hours  before  being  killed,  weigh  it,  cut  it  in  small 
pieces,  and  rub  it  up  with  ten  times  its  weight  of  raw  fibrin, 
and  add  to  the  whole  twelve  or  fifteen  parts  of  water  at  45 °C. 
Keep  the  whole  at  this  temperature  for  four  to  six  hours, 
stirring  frequently  ;  then  add  a  little  acetic  acid,  and  boil  to 
coagulate  albumin.  Filter  through  a  piece  of  linen,  and  evapo- 
rate the  filtrate  quickly  to  a  syrup.  Pour  it,  while  still  hot, 
into  a  flask,  and  add  strong  spirit  to  it  till  a  distinct  flocculent 
precipitate  occurs.  Let  it  cool ;  filter,  and  distil  the  filtrate 
till  it  forms  a  thick  pulp  while  still  warm.  Let  it  stand  for  a 
day  in  the  cold  to  allow  complete  crystallization  to  take  place ; 
then  throw  it  on  a  filter,  and  let  the  mother  liquor  drain  com- 
pletely away ;  wash  the  residue  with  a  little  cold  water,  and 
then  put  it  into  a  large  quantity  of  water  at  50°  C,  which  will 
dissolve  the  leucine  and  leave  the  tjM-osine.  Dissolve  the 
tyrosine  in  hot  water,  let  it  crystallize  out,  and  then  dissolve 
it  again  in  ammonia  and  re-crystallize. 


522  DIGESTION. 

INTESTINAL   JUICE. 

172.  Intestinal  juice  was  first  obtained  pure  by  Thiry,  who 
divided  the  jejunum  or  ileum  in  two  places  at  a  distance  of  10 
to  15  centimetres  from  each  other,  sewed  up  one  end  of  the 
piece  thus  isolated,  and  attached  the  other  to  the  wound  in 
the  abdominal  walls.  The  short  cul-de-sac  of  intestine  formed 
in  this  manner  remained  attached  to  the  mesentery,  and  its 
vessels  and  nerves  being  uninjured,  it  yielded  a  normal  secre- 
tion which  could  thus  be  collected  without  admixture  with 
other  digestive  secretions  and  products.  The  continuity  of 
the  alimentary  canal  was  restored  by  sewing  together  the 
divided  ends  of  intestine. 

173.  Intestinal  Fistula. — The  method  employed  by 
Thiry  has  been  somewhat  modified  by  Paschutin,  who  prefers 
the  duodenum  and  the  beginning  of  the  jejunum,  a  part  of  the 
small  intestine  which  yields  a  very  active  secretion.  In 
making  a  fistula  by  his  method,  the  hair  must  be  carefully 
removed  from  the  skin,  and  an  incision  3  to  5  centimetres 
long  made  in  the  linea  alba.  The  duodenum  is  drawn  out  and 
two  stout  ligatures  passed  round  it  about  two  and  a  half  cen- 
timetres beyond  the  spot  where  it  separates  from  the  pancreas. 
The  ligatures  having  then  been  separated  from  each  other  and 
tightened,  the  intestine  is  divided  between  them.  The  upper 
end  of  the  duodenum  is  then  replaced  in  the  abdomen. 

The  next  step  in  the  operation  is  to  divide  the  jejunum  in  a 
similar  manner.  The  most  obvious  method  of  accomplishing 
this  would  be  to  follow  the  intestine  down  to  the  point  at 
which  the  second  division  is  to  be  made.  This  is,  however, 
rendered  impossible  b}r  the  extreme  shortness  of  the  mesentery 
at  the  point  where  the  duodenum  ends  in  the  jejunum.  It  is, 
therefore,  necessaiy  to  find  the  jejunum  independently,  by 
following  the  intestine  upwards  from  any  loop  which  may 
present  itself  in  the  wound.  It  is  obvious,  however,  that  be- 
fore this  can  be  done,  the  operator  must  find  out  in  what  di- 
rection the  intestine  must  be  followed.  For  this  purpose,  the 
loop  being  held  tight  between  the  finger  and  thumb,  a  quantity 
of  half  per  cent,  salt  solution  is  injected  into  the  lower  cut  end 
of  the  duodenum,  by  a  syringe  with  a  conical  nozzle,  which  is 
passed  through  the  tightened  ligature.  As  the  fluid  passes 
downwards  until  it  meets  the  obstruction  presented  by  the 
fingers,  the  upper  part  of  the  loop  is  at  once  recognized  by  its 
becoming  full.  The  distended  gut  is  then  followed  up  till  the 
beginning  of  the  jejunum  is  reached,  which  is  recognized  by 
the  mesentery  becoming  shorter.  Two  ligatures  are  passed 
round  it,  and  the  intestine  divided  between  them  as  before. 
The  under  end  is  replaced  in  the  abdomen,  and  the  upper  end 
closed  by  sutures  so  as  to  form  the  cul-de-sac.     Before  doing 


BY    DR.   LAUDER   BRUNTON.  523 

so,  the  bundle  of  mesenteric  vessels  leading  to  the  part  con- 
stricted by  the  ligature  must  be  compressed  between  the  finger 
and  thumb,  while  the  constricted  part  is  cut  off.  As  it  is 
necessary  that  the  serous  surfaces  should  be  in  apposition, 
the  mucous  membrane,  which  is  turned  outwards  by  the  con- 
traction of  the  muscular  coat,  must  be  first  turned  inwards, 
and  the  closure  affected  by  sutures,  applied  as  shown  in  fig. 

318.  The  closed  end  is  then  replaced  in  the  abdomen,  and  the 
continuity  of  the  intestine  again  restored  by  joining  the  cut 
ends  of  the  duodenum  and  jejunum.  In  doing  this,  the  two 
ligatures,  with  the  parts  constricted  by  them,  must  be  cut  off 
in  the  manner  previously  directed.  The  ligatures  applied  to 
the  vessels  should  include  a  little  of  the  adjoining  intestinal 
wall,  so  as  to  give  them  a  firmer  hold.  The  two  cut  ends  are 
now  brought  into  apposition,  and  the  ligatures  firmly  tied  to- 
gether so  as  to  retain  the  ends  in  their  proper  relation,  and 
held  in  the  hand  of  an  assistant  The  first  stitch  is  put  through 
the  intestines  in  such  a  way  as  to  include  both  bundles  of  ves- 
sels, and  should  be  drawn  very  tight  and  tied,  so  that  it  not 
only  unites  the  ends,  but  serves  as  an  additional  ligature  for 
the  vessels. 

To  prevent  the  ligature  from  cutting  the  intestine,  it  should 
either  be  made  of  very  thick  soft  silk,  or  of  two  or  three  fine 
ligatures  used  together.  Five  or  six  similar  stitches  made  at 
a  little  distance  from  each  other  on  each  side  of  the  first  are 
sufficient  to  join  the  mesenteric  edge  of  the  two  pieces  of  in- 
testine, which  then  lie  with  their  axes  parallel  (fig.  318).  To 
complete  the  junction,  the  two  ends  must  be  brought  into  the 
same  straight  line  and  sewn  together.  The  application  of  the 
final  sutures  is  a  matter  of  considerable  difficulty,  principally 
on  account  of  the  tendency  of  the  mucous  membrane  to  become 
everted.  The  mode  of  applying  the  sutures  so  as  to  accomplish 
this  object,  will  be  at  once  understood  by  a  reference  to  fig. 

319.  Several  threads,  each  with  a  needle  at  each  end,  must  be 
prepared.  For  the  first  suture,  one  needle  enters  the  intestine 
from  its  serous  aspect  at  a,  and  is  brought  out  at  b,  the  other 
enters  at  a',  and  is  brought  out  at  b'.  The  two  ends,  b  and  &', 
are  drawn  tight  and  knotted  together.  For  the  second  suture, 
one  needle  enters  at  b,  and  is  brought  out  at  c,  the  other  enters 
at  b',  and  is  brought  out  at  c',  and  so  on.  To  conclude  the 
operation,  the  wound  in  the  abdominal  wall  is  brought  together 
by  sutures,  and  the  open  end  of  the  cul-de-sac  sewn  into  it. 
It  is  also  desirable  that  the  junction  of  the  divided  intestine 
should  be  secured  to  the  wound  by  a  suture,  in  order  to  pre- 
vent the  induction  of  general  peritonitis  by  its  locomotion. 

**  174.  Artificial  Intestinal  Juice. — Remove  the  small 
intestine  from  a  pig,  dog,  or  rabbit,  as  soon  after  death  as 
possible  ;  put  a  ligature  round  its  upper  end,  attach  the  lower 


524  DIGESTION. 

end  to  the  tap,  and  fill  it  with  water  under  pressure.  Close 
the  lower  end  by  compressing  it  between  the  finger  and  thumb, 
and  raise,  first  the  one  end,  and  then  the  other,  so  that  the 
water  may  loosen  the  contents  of  the  intestine  from  its  walls. 
Empty  out  the  water,  and  repeat  the  process  three  or  four 
times,  until  what  flows  from  the  intestine  is  either  transparent 
or  only  slightly  opalescent,  and  is  not  at  all  tinged  with  bile. 
Five  minutes'  washing  is  generally  sufficient  to  cleanse  the  in- 
testine thoroughly.  It  should  not  be  continued  longer  than 
is  necessary,  as  otherwise  a  great  part  of  the  intestinal  ferment 
may  be  removed.  Slit  up  the  intestine,  and  separate  the  mu- 
cous membrane  from  the  muscular  layer.  Cut  the  mucous 
membrane  into  small  pieces  with  scissors,  or  rub  it  up  in  a 
mortar  with  sand  or  pounded  glass,  then  mix  it  with  three  to 
six  times  its  bulk  of  water,  and  let  it  stand  for  a  quarter  of  an 
hour  to  two  hours.  Filter  the  infusion  through  muslin,  and 
then  through  paper. 

**  175.  Actions  of  Intestinal  Juice. — 1.  It  converts 

Starch  into  Sugar Add  a  little  of  the  artificial  juice  to  some 

starch  mucilage,  warm  it,  and  test  for  sugar  as  described  in  §  77 
or  155.  The  mucilage  and  juice  alone  should  also  be  tested,  in 
order  to  be  sure  that  neither  of  them  contains  sugar.  2.  It  con- 
verts Cane  Sugar  into  Grape  Sugar. — Dissolve  some  cane 
sugar  in  water,  and  apply  Trommer's  test  to  a  portion  of  the 
solution.  No  reduction  of  the  copper  will  occur  as  it  would 
do  if  grape  sugar  were  employed.  Add  some  artificial  intesti- 
nal juice  to  another  portion  of  the  solution.  Let  it  stand  at 
40°  for  a  short  time,  and  then  apply  Trommer's  test ;  a  re- 
duction of  the  copper  will  take  place.  A  similar  conversion 
of  cane  into  grape  sugar  is  produced  by  boiling  with  acids,  as 
may  be  shown  by  boiling  a  little  of  the  syrup  with  dilute  sul- 
phuric acid,  and  then  applying  Trommer's  test. 

*  176.  Moreau's  Experiment. —  When  all  the  Nerves 
going  to  a  part  of  the  Intestine  are^divided,  it  secretes  a  very 
large  Quantity  of  a  ivatery  Intestinal  Juice. — This  is  shown  by 
letting  a  large  dog  fast  for  at  least  twenty-four  hours,  so  that 
its  intestines  may  be  empty.  It  is  then  put  under  chloroform, 
an  incision  made  in  the  linea  alba,  and  a  loop  of  intestine  drawn 
out.  Two  ligatures  are  tied  firmly  round  it  at  a  distance  of 
four  or  five  inches  apart,  so  that  the  piece  of  bowel  between 
them  is  completely  isolated  from  the  rest  of  the  intestine.  All 
the  nerves  in  the  mesentery  belonging  to  this  piece  are  then 
carefully  divided,  leaving  the  vessels  uninjured.  Another  liga- 
ture is  then  tied  round  the  intestine  on  each  side  of  the  first 
two,  and  about  four  or  five  inches  from  them,  so  that  a  piece  of 
intestine  similar  to  the  first  is  isolated  on  each  side  of  it,  but 
the  nerves  going  to  them  are  left  untouched.  The  intestine  is 
then  returned  to  the  abdominal  cavity,  the  wound  sewn  up,  and 


BY    DR.    LAUDER    BRUNTON.  525 

the  animal  left  for  four  or  five  hours.  It  is  then  killed,  and 
the  intestines  examined.  The  part  of  which  the  nerves  have 
been  divided  is  found  perfect^*  full  of  fluid,  while  the  piece  on 
each  side  of  it  is  empty.  The  fluid  contained  in  the  distended 
loop  has  been  ascertained  by  Kiihne  to  resemble  in  composition 
diluted  intestinal  juice. 

177.  Movements  of  the  Intestine. — The  influence  of 
the  nervous  s}'stem  on  the  movements  of  the  intestine  has  not 
yet  been  completely  investigated.  Peristaltic  action  is  in  all 
probability  produced  by  the  ganglia  in  the  intestinal  walls,  as 
it  continues  in  an  excised  portion  ;  but  it  may  be  increased  by 
the  action  of  the  vagi,  and  lessened  or  arrested  by  the  splanch- 
nics.  The  ganglia  are  stimulated  and  movements  excited  by 
the  presence  of  venous  blood  in  the  intestinal  vessels  (Maier 
and  Von  Basch),  or  their  distension  by  arterial  blood  (Nasse). 
The  splanchnics  are  inhibitory  nerves  for  the  intestine,  and 
its  movements  are  arrested  by  their  irritation  (Pfluger  and 
Westphal).  At  a  certain  period  after  death,  however,  they  ex- 
cite movements  (Ludwig  and  Spiess).  It  is  uncertain  whether 
they  exert  an  inhibitor}'  action  directly  on  the  ganglia  as  the 
vagus  does  in  the  heart,  or  act  only  indirectly  through  the  ab- 
sence of  blood  which  they  produce  by  causing  contraction  of 
the  vessels.  For  a  description  of  the  method  of  showing  the 
action  of  the  splanchnics,  see  Ludwig  and  Spiess  ;  Sitzungsbe- 
richte  der  Wiener  Academie,  xxv.  1857,  p.  580.  Their  inhibi- 
tory power  is  said  by  Koliker  to  be  destroyed  by  curare,  and 
the  writer  has  been  unable  to  observe  it  in  several  experiments 
on  animals  narcotized  by  chloral.  Irritation  of  the  vagi  causes 
movements  of  the  intestine,  beginning  in  the  stomach.  This 
occurs  only  occasionally  when  one  or  both  splanchnics  are  in- 
tact, but  almost  invariably  after  both  have  been  divided 
(Houckgeest).  In  performing  this  experiment,  as  well  as 
others  on  the  intestine,  it  is  advisable  to  employ  Sanders-Ezn's 
method,  of  opening  the  abdomen  under  f  per  cent,  salt  solution 
warmed  to  35°  C,  in  order  to  avoid  the  irritation  to  the  intes- 
tines which  is  occasioned  by  their  exposure  to  air.  For  this 
purpose,  a  bath  of  tin  or  zinc,  32  inches  long,  by  9£  broad,  and 
8^  deep,  provided  with  a  Geissler's  regulator  at  one  end,  is 
used,  into  this  thirty-five  litres  of  water  at  35°  C.  are  poured, 
and  sufficient  salt  added  to  make  a  |  per  cent,  solution.  In- 
stead of  measuring  out  the  water  each  time,  it  is  more  conven- 
ient to  mark  on  the  sides  of  the  bath  the  height  to  which  it 
should  be  filled.  The  animal,  being  laid  on  a  piece  of  board 
with  Czermak's  holder  attached  to  it,  instead  of  the  usual  sup- 
port, is  placed  in  the  bath,  and  the  lower  end  of  the  board  is 
kept  immersed  by  attaching  a  weight  to  it.  For  detailed  ex- 
periments with  this  method,  see  Houckgeest  Pfiiiger's  Archiv. 
vi.  p.  266. 


526  THE   SECRETIONS. 


CHAPTER  XXXVIII. 

THE  SECRETIONS. 
Section  I. — Milk. 

178.  Characters  of  Milk. — Newly-drawn  milk  is  an 
opaque  fluid  of  a  white  or  yellowish-white  color.  Its  color 
and  opacity  are  due  to  its  being  an  emulsion,  i.  e.,  to  its  con- 
sisting of  little  globules  of  fat  suspended  in  a  solution  of 
albumin,  milk,  sugar,  and  organic  salts.  Each  globule  of  fat 
is  covered  by  a  thin  coating  of  casein.  When  the  milk  is 
allowed  to  stand,  the  fat  globules,  being  lighter  than  the  fluid 
in  which  they  swim,  rise  in  great  part  to  the  top,  and  form 
cream,  and  the  lower  part  of  the  fluid  often  acquires  a  bluish 
tinge.  A  similar  separation  also  takes  place  in  the  milk  gland 
itself,  so  that  the  milk  last  drawn  is  richest  in  cream.  The 
globules  of  fat  are  prevented  from  uniting  by  the  thin  albumi- 
nous coating  which  surrounds  each ;  but  when  this  is  broken 
bj-  agitation,  they  coalesce,  forming  butter.  Changes  also 
occur  in  the  milk,  sugar,  casein,  and  fats  of  the  milk,  more  or 
less  quickly,  according  to  the  higher  or  lower  temperature  to 
which  it  is  exposed.  The  milk-sugar  becomes  converted,  ap- 
parently through  the  agency  of  a  ferment,  into  lactic  acid. 
This  gives  the  milk  an  acid  reaction,  and  precipitates  the  case- 
in, causing  the  milk  to  curdle.  The  coagulum,  or  curd,  in- 
closes the  fat  globules.  The  liquid  from  which  it  is  separated, 
a  solution  of  milk,  sugar,  and  salts,  is  known  as  whey.  The 
curd,  when  completely  separated  from  the  whey,  is  called 
cheese. 

Microscopical  Examination. — Examine  milk  under  the  mi- 
croscope. It  will  be  seen  to  consist  of  a  colorless  fluid,  con- 
taining large  numbers  of  minute  fat  globules.  Add  a  drop  of 
acetic  acid,  so  as  to  dissolve  the  coating  of  casein  :  the  globules 
will  coalesce.  Besides  these  globules,  cells  containing  much 
fat  ma}r  be  seen,  and  also  masses  of  fat  similar  to  those  within 
the  cells,  but  destitute  of  an  envelope.  These  cells  are  found 
much  more  frequently  in  the  milk  (called  colostrum)  which  is 
secreted  for  the  first  few  days  after  parturition,  and  they  have, 
therefore,  received  the  name  of  colostrum  corpuscles.  They 
sometimes  exhibit  contractile  movements. 

Reaction. — The  reaction  of  human  milk  is  always  alkaline, 
and  that  of  cows'  milk  is  generally  so.     Free  lactic  acid  always 


BY    DR.    LAUDER   BRUNTON.  527 

exists  in  the  fresh  milk  of  the  carnivora,  and  occasionally  in 
that  of  the  cow  and  goat. 

Specific  Gravity The  specific  gravity  may  be  taken  by 

the  specific  gravity  bottle  or  by  a  hydrometer.  Before  using 
either,  the  milk  should  be  well  shaken  and  air-bubbles  removed. 

With  a  view  to  the  detection  of  adulteration  by  water,  a 
special  hydrometer  is  used,  which  is  known  as  Quevenne's 
lacto-densimeter.  It  is  furnished  with  a  scale  indicating 
specific  gravities  from  1042  to  1014.  The  highest  specific 
gravity  of  milk  yet  observed  is  1040  to  1041,  and  the  average 
specific  gravity  of  milk  mixed  with  50  per  cent,  of  water  is 
1014  to  1016.  The  instrument  is  graduated  for  use  at  15°  C, 
and  when  employed  at  a  different  temperature,  a  correcti*i 
must  be  made  in  the  specific  gravity  indicated  by  it.  Tables 
for  this  purpose  are  to  be  found  in  Gorup-Besanez's  Zoochemie, 
3d  edition,  p.  468.  The  quantity  of  water  mixed  with  a 
sample  of  milk  may  be  approximately  estimated  by  the  sub- 
joined tables. 

The  specific  gravit}r  of  milk,  with  the  cream  thoroughly 
mixed  with  it  by  shaking,  is  first  ascertained,  and  if  the  result 
is  doubtful,  another  observation  is  made  after  the  cream  has 
been  removed. 

Table  for  estimating  the  quality  of  milk  by  its  specific 
gravity  before  the  removal  of  the  cream : — 

Specific  Gravity. 

1033  to  29  =  Pure  milk. 
1029  "  26  =  Milk  with  10  per  cent,  of  water. 
1026  "  23  =  "         20         "  " 

1023  "  20   =  "         30         "  " 

1020  "   17   =  "         40         "  " 

1017  "  14   =  "         50         "  " 

Table  for  estimating  the  quality  of  milk  from  which  the 
cream  has  been  removed,  by  its  specific  gravity : — 

Specific  Gravity. 

1037  to  1033  =  Pure  milk. 

1033  "  1029  =  Milk  with  10  per  cent,  of  water. 

1029  "  1026  =  "  20         "  " 

1026  "  1023  =  "  30         "  " 

1023  "  1020  =  "  40         "  " 

1020  "   1016  =  "  50         "  " 

**179.  Constituents  of  Milk. —  Casein. — Casein  closely 
resembles  alkali-albuminatu'  in  its  characters.     It  is  not  pre- 

1  Casein  is  usually  regarded  as  identical  with  alkali-albuminate.  The 
recent  researches  of  Hoppe-Seyler  and  Lubavin  on  its  digestion  in  gas- 
tric juice,  tend  to  show  that  it  consists  of  an  albuminous,  in  combina- 
tion with  a  non-albuminous,  organic  body. 


528  THE    SECRETIONS. 

cipitated  by  boiling.  It  is  soluble  in  alkaline  solutions,  and  is 
precipitated  from  them  by  neutralization,  but  this  precipitation 
is  prevented  by  the  presence  of  alkaline  phosphates.  It  dis- 
solves in  excess  of  hydrochloric  acid,  and  also,  but  not  so 
readily,  in  acetic  acid.  Milk  does  not  coagulate  when  it  is 
boiled  in  a  test-tube,  but  if  it  is  boiled  in  an  evaporating  basin, 
the  casein  near  the  surface  becomes  somewhat  dried  and  forms 
a  scum  on  the  surface;  and  if  this  is  removed  another  appears. 
When  milk  stands  in  a  warm  place,  it  becomes  sour  and  curdles. 
»If  common  salt  is  added  to  fresh  milk,  it  becomes  sour  on  stand- 
ing, but  does  not  curdle,  for  the  albumin,  separated  from  the 
casein  by  the  acid,  is  kept  in  solution  by  the  neutral  salt.  If 
tfl!e  solution  is  boiled,  the  albumin  is  coagulated. 

Mode  of  Separating  Casein. —  As  alkaline  phosphates  are 
contained  in  milk,  it  must  be  not  merely  neutralized  but  ren- 
dered distinctly  acid,  in  order  to  precipitate  the  casein.  The 
precipitation  is  not  complete  unless  the  milk  is  diluted. 

Add  a  little  acetic  acid  to  milk  and  warm  it  to  40°  C.  The 
casein  and  the  greater  part  of  the  fat  separates  in  large  flakes. 
Moisten  a  plaited  filter  with  water,  and  lilter  the  milk  ;  put  the 
filtrate  aside,  wash  the  coagulum  thoroughly  with  water,  and 
remove  the  fat  by  exhausting  it  with  a  mixture  of  alcohol  and 
ether  in  the  apparatus  described  in  App.  §  207.  Put  this  solu- 
tion aside;  the  remaining  coagulum  is  casein.1 

Mode  of  Separating  Albumin. — Boil  the  filtrate  from  which 
the  casein  has  been  precipitated.  A  precipitate  of  albumin 
will  be  produced.  Albumin  may  also  be  separated  by  filtering 
milk  through  a  porous  cell  or  cone  by  exhausting  the  air.  A 
clear  fluid  will  pass  through  which  will  not  be  precipitated  by 
acetic  acid,  showing  that  no  casein  is  present,  but  will  be  pre- 
cipitated by  boiling  or  by  nitric  acid.  In  the  acid  liquid  from 
which  the  coagulable  albumin  has  been  removed  by  boiling,  a 
precipitate  is  produced  by  Millon's  reagent,  although  none  is 
occasioned  by  the  addition  of  nitric  acid  or  mercuric  chloride. 

Milk-Sugar. — Filter  the  rest  of  the  fluid  in  which  the  albu- 
min has  been  coagulated.  Shake  it  with  ether  to  dissolve  out 
the  fat ;  remove  the  ether  with  a  pipette,  and  then  evaporate 
the  fluid  to  a  thin  syrup.  The  milk-sugar  will  crystallize  out 
gradually  in  rhombic  prisms.  It  differs  from  glucose  in  its 
crystalline  form  (the  latter  generally  occurring  in  warty  crumb- 
ling masses),  in  fermenting  less  readily,  and  in  being  insoluble 
in  absolute  alcohol. 

The  Inorganic  Salts  of  milk  are  chlorides,  sulphates,  phos- 

1  The  casein  in  human  milk  cannot  be  readily  precipitated  by  hydro- 
chloric or  acetic  acids,  and  in  order  to  obtain  it,  magnesium  sulphate 
must  be  added  until  the  casein  is  precipitated,  and  the  precipitate  must 
be  washed  with  a  strong  solution  of  this  salt,  and  then  with  alcohol  and 
ether. 


BY   DR.    LAUDER   BRUNTON.  529 

pbates  and  carbonates  of  the  alkaline  and  earthy  bases.  They 
can  only  be  investigated  in  the  ash.  For  the  method  of  igni- 
tion see  §  214. 

Fats. — The  fats  may  be  separated  by  either  of  the  following 
methods:  1.  Evaporate  the  mixture  of  alcohol  and  ether  with 
which  the  coagulum  was  exhausted,  and  the  fat  remains. 

2.  Add  to  15  or  20  c.  c.  of  milk,  10  c.  c.  of  a  moderately  strong 
solution  of  caustic  soda;  shake  it  vigorously  with  twice  or 
thrice  its  volume  of  ether.  Remove  the  laj^er  of  ether,  and 
evaporate  it  in  a  water  bath,  and  the  fat  remains.  Ether  does 
not  remove  the  fat  from  fresh  milk,  as  the  casein  envelops  the 
globules,  and  protects  the  fat  from  its  action ;  but  soda  dis- 
solves these  envelopes.  Ether  will  remove  90  per  cent,  of  the 
butter  from  milk  which  has  become  acid  by  standing. 

**  180.  Mode  of  Estimating  the  Quantity  of  Butter 
Contained  in  Milk. — A  rough  method  of  doing  this,  is  to 
measure  the  cream  which  separates  from  it  by  Chevallier's  cre- 
mometer.  This  is  a  cylindrical  vessel,  graduated  into  a  hun- 
dred parts.  The  percentage  amount  of  cream  is  indicated  by 
the  number  of  divisions  it  occupies  when  the  vessel  is  filled  with 
milk  to  the  zero  point.     This  method  is  quite  unreliable. 

VogeVs  Test. — A  much  more  exact  method  is  that  devised 
by  Vogel,  which  depends  on  the  fact  that  the  opacity  of  milk 
is  due  to  the  globules  it  contains,  and  is  in  proportion  to  their 
number. 

The  apparatus  required  for  this  test  are — 1.  A  cylindrical 
bottle,  in  which  to  mix  the  milk  and  water.  It  should  hold 
about  200  c.  c,  and  have  a  mark  on  the  side  at  the  height  of 
100  c.  c.  2.  A  test-glass,  with  parallel  glass  sides,  exactly  ^  a 
centimetre  apart,  and  supported  vertically  on  a  metal  foot.  3. 
A  pipette  graduated  in  fifths  of  a  cubic  centimetre. 

Application  of  the  Test. — Before  applying  this  test,  it  must 
be  ascertained  by  microscopical  examination  that  the  milk  does 
not  contain  starch  granules,  or  any  other  impurity  in  suspen- 
sion which  might  increase  its  opacity.  Fill  the  bottle  up  to 
the  100  c.  c.  mark  with  clear  spring  water.  Fill  the  pipette  up 
to  zero  with  milk  (App.  §  217),  and  let  3  c.  c.  run  into  the  bottle. 
Mix  it  well  with  the  water,  and  fill  the  test-glass  with  the  mix- 
ture. Put  it  in  a  tolerably  dark  room,  place  a  stearine  candle 
at  a  distance  of  about  three  feet  from  it,  and  look  at  the  candle 
through  the  glass.  If  the  contour  of  the  flame  can  be  readily 
perceived,  pour  the  liquid  back  into  the  bottle,  add  another  ^ 
c.  C.  of  milk  to  it,  shake  it,  and  look  at  the  candle  through  it 
again.  Repeat  this  till  the  outlines  of  the  flame  can  no  longer 
be  recognized.  Then  add  together  the  different  quantities  of 
rnilk,  so  as  to  find  the  total  amount  which  has  been  added,  and 
then  ascertain  by  the  following  table  how  much  butter  the  milk 
contains  : — 
34 


530  THE    SECRETIONS. 

1.0  c.  c.  milk,  corresponds  to  23.43  per  cent,  of  butter. 


1.5 

tt 

u 

15.46 

tt 

tt 

2.0 

tt 

u 

11.83 

tt 

tt 

2.5 

tt 

u 

9.51 

tt 

tt 

3.0 

If 

u 

7.96 

tt 

tt 

3.5 

tt 

u 

6.86 

tt 

tt 

4.0 

t( 

(( 

6.03 

tt 

tt 

4.5 

l( 

t( 

5.38 

tt 

tt 

5.0 

tt 

tt 

4.87 

tt 

tt 

5.5 

u 

u 

4.45 

tt 

tt 

6.0 

u 

11 

4.09 

tt 

tt 

6.5 

tt 

u 

3.80 

tt 

tt 

7.0 

tt 

u 

3.54 

tt 

tt 

7.5 

tt 

u 

3.32 

tt 

tt 

8.0 

tt 

u 

3.13 

tt 

tt 

8.5 

It 

u 

2.96 

tt 

tt 

9.0 

u 

u 

2.80 

tt 

.  tt 

9.5 

tt 

t< 

2.77 

tt 

tt 

10.0 

u 

u 

2.55 

tt 

tt 

11 

tt 

(( 

2.43 

tt 

tt 

12 

tt 

a 

2.16 

tt 

tt 

13 

u 

(( 

2.01 

tt 

tt 

14 

it 

(C 

1.88 

tt 

tt 

15 

u 

u 

1.78 

tt 

tt 

16 

tt 

u 

1.68 

tt 

tt 

17 

u 

a 

1.60 

tt 

tt 

18 

tt 

u 

1.52 

tt 

tt 

19 

tt 

u 

1.45 

tt 

tt 

20 

tt 

u 

1.39 

tt 

tt 

22 

u 

u 

1.28 

tt 

tt 

24 

tt 

u 

1.19 

tt 

tt 

26 

u 

(t 

1.12 

tt 

tt 

28 

tt 

I. 

1.06 

tt 

tt 

30 

u 

(4 

1.00 

tt 

tt 

35 

tt 

tc 

0.89 

tt 

tt 

40 

tt 

u 

0.81 

tt 

tt 

45 

u 

11 

0.74 

tt 

tt 

50 

tt 

u 

0.69 

tt 

tt 

55 

u 

11 

0.64 

tt 

tt 

60 

tt 

a 

0.61 

tt 

tt 

70 

it 

it 

0.56 

tt 

tt 

80 

u 

tt 

0.52 

tt 

tt 

90 

u 

it 

0.48 

tt 

tt 

100 

u 

tt 

0.46 

tt 

tt 

If  cream  is  to  be  tested,  only  one  cubic  centimetre  is  to  be 
added  at  first,  and  a  half  c.  c.  at  a  time  afterwards. 

Vogel  found  that  about  6  c.  c.  of  pure  cow's  milk,  or  3.7  of 


BY    DR.    LAUDER    BRUNTON.  531 

cream,  added  to  100  c.  c.  of  water,  were  sufficient  to  form  a  mix- 
ture which  quite  obscured  a  caudle  flame.  When  8  c.  c.  are 
required,  the  milk  contains  about  30  per  cent,  more  water  than 
it  ought  to  do,  either  from  the  addition  of  water,  or  of  creamed 
milk.  When  12  c.  c.  are  necessary,  the  milk  contains  50  per 
cent,  too  much  water. 

THE  URINE. 

**  181.  Characters  of  Urine. — The  healthy  urine  of  man 
is  a  clear  liquid  of  a  golden  color,  possessed  of  a  characteristic 
odor,  and  having  a  specific  gravity  which  generally  varies  from 
1018  to  1023,  although  it  may  sink  as  low  as  1005,  or  rise,  under 
opposite  circumstances,  as  high  as  1030. 

The  reaction  of  the  mixed  urine  of  man  under  normal  circum- 
stances is  acid.  By  the  term  mixed  urine,  we  understand  a 
mixture  of  the  different  portions  of  urine  passed  during  twenty- 
four  hours. 

When  urine  is  allowed  to  stand  for  some  hours,  it  deposits  a 
slight  cloudy  sediment,  which  is  called  the  mucous  cloud,  and 
which  consists  of  mucus  holding  in  suspension  a  few  epithelial 
cells,  derived  from  the  genito-urinary  passages.  It  is  usually 
affirmed  that  the  urine,  on  exposure  to  the  air,  in  clean  vessels, 
becomes,  after  some  hours,  much  more  acid  than  it  was  when 
passed.  To  this  change  the  name  of  the  acid  fermentation  has 
been  given.  There  are  no  facts  which  prove  the  constant  occur- 
rence of  this  acid  change.  When  the  urine  is,  however,  placed 
for  periods  which  vary  very  greatly,  in  open  vessels,  exposed  to 
air,  it  ultimately  invariably  undergoes  the  so-called  alkaline 
fermentation,  i.e.,  its  reaction  becomes  exceedingly  alkaline,  it 
emits  an  ammoniacal  odor,  and  it  becomes  turbid,  in  conse- 
quence of  the  precipitation  of  phosphate  of  magnesium  aud  am- 
monium, of  phosphate  of  calcium,  and  urate  of  ammonium. 

The  acid  reaction  of  healthy  human  urine  is  probably  due,  in 
great  part,  to  free  carbonic  acid,  to  uric  and  to  hippuric  acids  ; 
it  has  been  commonly  believed,  however,  that  acid  phosphate 
of  sodium  exists  in  urine,  and  that  the  acidity  of  the  fluid  is 
chiefly  due  to  its  presence. 

The  alkaline  reaction  of  urine  which  has  become  decom- 
posed is  undoubtedly  due  to  carbonate  of  ammonium.  Un- 
der the  influence  of  putrescent  animal  substances  it  may  be 
observed  that  perfectly  fresh  urine  becomes,  in  the  course  of 
an  hour  or  two,  intensely  foetid.  Under  these  circumstances, 
the  urea  contained  in  urine  combines  with  the  elements  of 
water  and  is  transformed  into  ammonium  carbonate  CH4N20-f 
H,0=»(NH4),CO^  The  following  experiments  throw  much 
light  on  the  proximate  causes  of  the  alkaline  fermentation  of 
urine : — 


532  TUE   SECRETIONS. 

Collect  200  cubic  centimetres  of  perfectly  fresh  urine  in  a 
vessel  which  has  been  carefully  washed  with  dilute  sulphuric 
acid,  and  afterwards  with  distilled  water.  Examine  the  reac- 
tion of  the  fluid,  which  will  be  found  acid,  then  divide  it  in  four 
equal  parts:  1st.  Pour  fifty  cubic  centimetres  into  a  clean 
beaker,  and  set  it  aside  to  serve  as  a  standard  with  which  to 
compare  the  other  portions. 

2d.  Place  fifty  cubic  centimetres  in  a  clean  beaker,  and  add 
to  it  a  few  drops  of  urine  which  lias  been  allowed  to  become 
foetid.  After  twent3'-four  hours  compare  this  sample  with  the 
first,  determining  the  following  points:  o,  smell,  which  will 
have  become  ammoniacal  in  the  second,  unchanged  in  the  first ; 
6,  clearness.  The  second  sample  will  have  become  opalescent, 
or  a  considerable  deposit  will  have  fallen ;  c,  reaction  will  be 
strongl}'  alkaline  in  the  second,  and  still  acid  in  the  first.  The 
alkaline  reaction  may  be  shown  to  be  due  to  the  presence  of  a 
volatile  alkali  by  heating  the  test-paper  which  has  been  used, 
and  observing  that  the  reaction  which  indicated  alkalinity  dis- 
appears on  the  application  of  heat ;  thus  the  blue  color  pro- 
duced when  reddened  litmus  paper  was  plunged  into  the  fluid, 
will  disappear,  and  again  give  place  to  red  when  the  paper  is 
heated. 

3d.  A  third  quantity  of  fifty  cubic  centimetres  is  placed  in 
a  Florence  flask  and  boiled  briskly  for  some  time,  then  a  plug 
of  clean  cotton  wool  is  inserted  into  the  neck  of  the  flask 
whose  contents  are  still  boiling,  and  is  thrust  down  by  means  of 
a  glass  rod.  The  urine  is  allowed  to  boil  for  some  minutes 
after  the  insertion  of  the  plug,  the  flask  is  then  allowed  to 
cool,  set  aside  for  many  weeks  and  then  examined. 

The  flask  containing  boiled  urine  and  protected  by  the  plug 
of  cotton  wool,  will,  if  the  operator  have  been  sufficient^ 
expert,  retain  its  transparency  and  its  acidity,  and  when 
examined  with  the  microscope  will  present  no  animal  or  vege- 
table forms.  On,  however,  exposing  the  contents  of  the  flask 
to  the  air,  the  alkaline  fermentation  will  soon  occur. 

182.  Enumeration  of  the  normal  constituents  of 
the  Urine. — The  normal  urine  of  man  consists  chiefly  of  a 
watery  solution  of  urea  and  common  salt,  mixed  with  smaller 
though  important  quantities  of  other  substances,  viz.,  hippuric 
acid,  creatinine,  uric  acid,  coloring  matters  yet  not  accurately 
investigated,  indican,  traces  of  fat,  besides  ammonium  and 
potassium  chlorides,  sulphates  of  potassium  and  sodium,  phos- 
phates of  calcium  and  magnesium,  acid  phosphate  of  sodium, 
silicic  acid  and  iron.  To  the  list  of  organic  substances  pres- 
ent in  urine,  we  may  add  unknown  substances  which  contain 
sulphur  and  phosphorus  in  an  unoxidized  condition,  besides 
well-known  bodies  which  are  certainly  present  in  the  urine  in 


BY    DR.    LAUDER    BRUNTON.  533 

certain  cases  of  disease,  but  which  cannot  positively  be  classed 
among  the  normal  constituents. 

The  abnormal  urine  of  man  may  contain  albumin,  grape- 
sugar,  lactic  acid  and  lactates  (?),  bile  coloring  matter  and  bile 
acids,  blood  serum  and  blood  cells,  haemoglobin,  pus  serum 
and  pus  cells,  carbonate  of  ammonium,  sulphuretted  hydrogen, 
oxalate  of  lime,  xanthine,  hypoxanthine,  leucine,  tyrosine,  and 
inosite. 

The  urine  may  contain,  in  addition  to  the  substances  which 
have  been  previously  named,  others  which  have  been  intro- 
duced into  the  bod}'  as  drugs  or  poisons,  and  which,  being 
excreted  b}'  the  kidneys,  find  their  way  into  the  urine ;  this  is 
the  case  with  many,  although  probably  not  with  all  the  metallic 
salts,  with  most  alkaloids,  and  with  organic  bodies  of  different 
constitution,  as  carbolic  acid,  alcohol,  and  various  vegetable 
coloring  matters. 

183.  Urinary  deposits. — Owing  to  deficiency  in  the  quan- 
tity of  the  urinary  water,  excess  in  the  quantity  of  normal 
ingredients,  or  presence  of  substances  which  are  not  normally 
present,  we  are  apt  to  have  urinary  sediments  or  deposits,  some 
of  which  are  composed  of  structural  elements,  not  usually 
present,  others  of  the  normal  or  abnormal  proximate  princi- 
ples. Amongst  such  sediments  we  find  most  frequently  uric 
acid,  urates,  ammoniaco-magnesian  phosphate,  calcium  phos- 
phate, calcium  oxalate,  blood  corpuscles,  mucus,  epithelium, 
pus,  etc. 

**  184.  Reactions  of  Urine  treated  -with  some  com- 
mon reagents. 

Before  commencing  a  systematic  account  of  the  mode  of 
separating  the  chief  constituents  of  urine,  the  student  may 
with  advantage  study  the  action  on  this  fluid  of  a  few  of  the 
common  reagents  which  indicate  the  presence  of  the  chief 
ingredients  contained.  Put  about  15  cubic  centimetres  of 
urine  into  a  series  of  test-tubes,  and  try  the  following  experi- 
ments:— 

1.  Add  about  5  cubic  centimetres  of^strong  nitric  acid.  No 
precipitate  will  occur,  either  immediately  or  after  standing  for 
some  time.  The  color  of  the  urine  will,  however,  become 
darker. 

2.  To  a  portion  of  fresh  urine  in  a  test-tube  add  an  equal 
volume  of  liquor  potassae.  After  some  time  a  transparent 
flaky  precipitate  will  be  observed,  which  separates  on  boiling, 
leaving  the  supernatant  fluid  of  its  original  color. 

By  other  experiments  it  may  be  shown  that  solutions  of  am- 
monia and  caustic  soda  likewise  induce  this  precipitate,  which 
consists  of  car//ii/  phoaphMes. 

3.  Add  to  15  cubic  centimetres  of  the  urine,  about  5  c.c.  of 
a  solution  of  silver  nitrate  (1-10)  ;  an  abundant  curdy  precipi- 


584  THE    SECRETIONS. 

tate  will  fall.  This  consists  of  chloride  of  silver  and  phosphate 
of  silver  ;  and  adding  nitric  acid  to  the  mixture,  the  phosphate 
of  silver  is  dissolved,  leaving  a  quantity  of  perfectly  white, 
chloride  of  silver,  which,  after  the  test-tube  has.  been  shaken 
for  some  time,  sinks  to  the  bottom,  leaving  a  clear  supernatant 
fluid. 

4.  To  15  cubic  centimetres  of  urine  which  have  been  strongly 
acidulated  with  nitric  or  hydrochloric  acid,  add  two  or  three 
c.c.  of  a  solution  of  barium  chloride.  A  precipitate  of  barium 
sulphate  will  fall. 

5.  Pour  a  strongly  acid  solution  of  ammonium  molybdate 
into  a  test-tube,  add  a  few  drops  of  urine  and  boil  ;  the  fluid 
will  become  yellow,  and  a  canary-yellow  precipitate  will  fall, 
composed  of  phospho-molybdate  of  ammonium  ;  this  indicates 
the  presence  of  phosphoric  acid. 

6.  To  15  cubic  centimetres  of  urine,  in  a  test-tube,  add  an 
equal  quantity  of  a  solution  of  caustic  baryta.  An  abundant 
precipitate  will  fall,  composed  chiefly  of  barium  sulphate  and 
phosphate. 

7.  To  the  same  quantity  of  urine  add  about  one-third  of  its 
volume  of  a  solution  of  acetate  of  lead.  A  white  precipitate, 
consisting  of  chloride,  sulphate  and  phosphate  of  lead,  will 
fall ;  and  it  will  be  observed  that  the  urine  is  to  a  great  extent 
decolorized. 

On  the  methods  of  Separating,  and  on  the  Reaction  of  TnE 
Principal  Organic  Constituents  of  Urine. 

**  185.  Preparation  of  Urea  (CH4N20)  from  Urine. 

— Take  100  cubic  centimetres  of  urine,  and  add  to  it  50  cubic 
centimetres  of  a  solution  made  by  mixing  one  volume  of  a 
saturated  solution  of  nitrate  of  barium,  with  two  volumes  of  a 
saturated  solution  of  caustic  baryta. 

A  precipitate  will  form,  which  is  chiefly  composed  of  phos- 
phate and  sulphate  of  barium.  On  filtering,  a  clear  fluid  is 
obtained  which  is  evaporated  to  dryness  on  awrater  bath.  The 
residue  is  treated  with  hot  spirits  of  wine,  and  the  alcoholic 
solution  is  likewise  evaporated  to  dryness.  On  now  adding 
absolute  alcohol  to  the  residue  the  urea  is  separated,  and  is 
obtained  from  the  solution  by  evaporation.  To  purify  it  further 
from  traces  of  other  organic  and  saline  matters,  the  crystals 
of  urea  must  be  colleeted  on  blotting-paper,  strongly  pressed 
between  folds  of  filtering  paper,  dried  on  a  porous  tile,  and,  if 
necessary,  again  dissolved  in  spirit  and  re-crystallized. 

Although  urea  can  be  readily  obtained  from  urine,  it  is  more 
convenient  to  make  use  of  artificial  urea  in  the  experiments 
which  are  required  to  demonstrate  its  characteristic  properties. 

As  it  is  altogether  beyond  the  province  of  this  book  to  refer 


BY    DR.    LAUDER    BRUNTON.  585 

to  matters  which  concern  pure  chemistry,  it  may  be  merely 
stated  that  the  artificial  urea,  which  can  now  be  readily  pur- 
chased, is  prepared  by  mixing,  in  certain  proportions,  aqueous 
solutions  of  potassium  cyanate  and  ammonium  sulphate,  eva- 
porating to  dryness  and  extracting  the  residue  with  alcohol. 
During  the  process  ammonium  cyanate  is  first  formed,  and  sub- 
sequently this  is  transformed  into  its  isomer,  urea.  In  order  to 
determine  the  chief  reactions  of  urea,  perform  the  following 
experiments : — 

1.  Take  a  crystal  of  urea,  and  placing  it  in  a  water-glass  add 
a  few  drops  of  distilled  water.  It  will  dissolve  with  great 
readiness.  Take  a  couple  of  drops  of  the  solution  and  allow 
it  to  crystallize  on  a  glass  slide,  which  may  be  gentl}-  heated. 
A  residue  is  obtained  which  presents  to  the  naked  eye  a  crys- 
talline appearance,  and  which  under  the  microscope  is  seen  to 
be  formed  of  transparent  four-sided  prisms,  terminated  by  one 
or  two  oblique  facets  (Fig.  322). 

2.  Place  a  fragment  of  urea  on  the  tongue,  and  observe  that 
it  possesses  a  cool,  nitre-like  taste. 

3.  Heat  a  fragment  of  urea  on  a  piece  of  platinum  foil,  or  on 
a  platinum  spatula,  over  a  gas  or  spirit-lamp.  The  urea  will 
first  melt,  then  solidify,  and  ultimately  burn  away  rapidly 
without  leaving  a  trace  of  ash  or  unburned  carbon. 

4.  Place  a  tiny  crystal  of  urea  on  a  glass  slide;  dissolve  it 
in  distilled  water,  and  then  add  a  drop  of  strong  and  perfectly 
colorless  nitric  acid.  Crystals  will  form  which  consist  of  a 
compound  of  nitric  acid  and  urea  (CH4Nv!0,HN0.1).  These  are 
much  less  soluble  than  crystals  of  urea.  Nitrate  of  urea  is 
comparatively  insoluble  in  dilute  nitric  acid.  Nitrate  of  urea 
crystallizes  generally  in  the  form  of  six-sided  tables  (Fig.  323). 

From  highly  concentrated  urine  of  man,  large  quantities  of 
nitrate  of  urea  may  be  sometimes  obtained,  without  any  pre- 
vious evaporation,  by  inerety  adding  pure  nitric  acid.  In  any 
case,  however,  nitrate  of  urea  may  be  obtained  in  a  crjrstalline 
form  by  evaporating  urine  nearly  to  a  S}rrupy  consistence,  de- 
canting the  liquid  from  the  salts  which  have  separated  out,  and 
then  adding  an  equal  volume  of  pure  nitric  acid. 

5.  Perform  an  experiment  similar  to  the  preceding  one, 
substituting  a  solution  of  oxalic  acid  for  the  nitric  acid.  A 
crystallization  of  oxalate  of  urea  (CH^N^OjC^H^Oj  is  obtained 
(Fig.  324). 

6.  Take  one  cubic  centimetre  of  a  solution  of  pure  urea  (con- 
taining 5  grammes  dissolved  in  100  grammes  of  distilled  water). 
Then  add  cautiously  a  solution  of  mercuric  nitrate;  a  curdy 
white  precipitate  forms,  which  consists  of  combinations  of  urea 
with  mercuric  oxide.  On  adding  a  drop  of  the  mixture  of  urea 
and  mercuric  nitrate  to  a  drop  of  a  cold  saturated  solution  of 
sodic  carbonate  no  reaction  will  be  observed  until  an  excess  of 


f>:5lj  THE    SECRETIONS. 

the  mercuric  salt  has  been  added.  Then  there  is  produced  a 
very  characteristic  3'ellow  color,  due  to  the  precipitation  of 
mercuric  hydrate.  On  this  reaction  is  based  Liebig's  method 
for  the  determination  of  urea. 

7.  Place  one  cubic  centimetre  of  a  solution  such  as  that  used 
in  the  last  experiment,  in  a  test-tube,  and  then  fill  the  latter 
exactly  with  a  solution  of  sodium  hypochlorite.  Invert  the 
tube  once  or  twice,  and  plunge  it  into  a  basin  containing  mer- 
cury. A  most  vigorous  evolution  of  gas  takes  place  ;  this  con- 
sists of  nitrogen. 

The  reaction  which  occurs  is  illustrated  by  the  following 
equation  : — 

CH4N20  +  3NaC10=3NaCl  +  C02+2n20  +  2N. 

The  carbonic  acid  which  is  generated  in  the  reaction  is  absorbed 
by  the  solution  of  sodium  hypochlorite. 

Instead  of  sodium  hypochlorite,  the  similar  salt  of  potassium 
or  calcium  might  be  used  in  this  experiment. 

**  186.  Separation  of  uric  acid  (C5H4N403)  from 
Urine. — Place  200  cubic  centimetres  of  urine  in  a  narrow  glass 
cylinder,  and  add  two  or  three  cubic  centimetres  of  pure  nitric 
acid.  After  twenty -four  hours  a  brick  colored  or  brown  sedi- 
ment will  have  subsided,  which  consists  of  crystals  of  uric  acid, 
strongly  tinted  with  the  coloring  matter  of  urine.  These  pre- 
sent, under  the  microscope,  the  most  various  forms,  the  more 
common  being  rhombic  tables  or  columns  and  lozenge-shaped 
crystals  ;  the  yellow  or  brown  color  which  such  crystals  pos- 
sess is  very  characteristic  of  uric  acid. 

Decant  the  urine  from  the  red  sediment  of  uric  acid,  which 
maybe  freely  washed  with  distilled  water,  as  uric  acid  requires 
14,000  times  its  weight  of  cold  and  1800  times  its  weight  of  hot 
water  to  dissolve  it.  The  sediment  may  then  be  collected  on 
filtering  paper  and  subjected  to  the  following  tests  : — 

1.  Place  a  small  quantity  of  the  crystals  on  a  microscopic 
slide,  and  add  a  drop  of  liquor  potassre.  The  crystals  dissolve, 
and  a  solution  of  urate  of  potassium  is  obtained  (C^H^K.^OJ. 

Now  add  carefully  an  excess  of  nitric  or  hydrochloric  acid, 
when  uric  acid  will  be  again  obtained  in  the  form  of  crystals, 
which  may  be  further  examined. 

It  may  be  well  to  state  that  uric  acid  often  occurs  as  a  de- 
posit in  urine  which  has  not  been  artificially  acidified,  and  that 
the  crystallographic  characters  of  the  substance  are  very  various 
and  sometimes  puzzling.  The  typical  crystals  of  uric  acid  are 
undoubtedly  rhombic  plates  with  extremely  obtuse  angles  ;  the 
typical  form  is,  however,  very  frequently  modified  ;  thus  spin- 
dle-shaped figures  are  formed  by  the  rounding  of  the  obtuse 
angles,  or  the  primary  form  is  so  modified  that  needles  are 
formed  which  occur  in  groups  (fig.  305).   Not  at  all  unfrequently 


BY    DR.    LAUDER    BRUNTON.  537 

wc  have  the  primary  form  so  modified  that  the  crystals  resemble 
hexagonal  plates.  Experience  gained  by  a  frequent  comparison 
with  accurate  drawings  of  the  various  forms  of  crystals  of  uric 
acid,  can  alone  enable  the  observer  rapidly  to  identify  uric  acid. 
When  any  doubts  exist  as  to  the  identity,  it  is  well  to  dissolve 
the  suspected  crystals  in  liquor  potassae,  and  to  proceed  as 
directed  above,  for  by  neutralizing  an  alkaline  urate  with  acid, 
some  of  the  commoner,  and  therefore  easily  identified  shapes  of 
uric  acid  ciystals,  are  obtained. 

2.  Place  a  very  small  quantity  of  the  reddish  ciystalline 
deposit  in  a  watch  glass  ;  add  four  or  five  drops  of  nitric  acid 
and  heat  very  cautiously  over  a  small  spirit-lamp  flame.  The 
uric  acid  will  dissolve,  and  on  evaporating  to  dryness,  a  red- 
dish-yellow residue  is  obtained.  On  exposing  this  residue  to 
the  vapor  of  ammonia,  or  adding,  by  means  of  a  thin  glass  rod, 
a  small  quantity  of  solution  of  ammonia,  a  beautiful  purple- 
red  color  is  developed,  which,  on  the  subsequent  addition  of  a 
little  solution  of  caustic  potash,  assumes  a  violet  tint.  This 
reaction  has  received  the  name  of  the  Murexide  Test. 

*187.  Separation  of  Hippuric  Acid  (C9H9NCg.— After 
urea,  hippuric  acid  is  the  organic  compound  present  in  largest 
quantity  in  the  urine  of  man,  the  mean  quantity  excreted  per 
diem  amounting  at  least  to  one  gramme.  The  difficulties  at- 
tending the  separation  of  hippuric  acid  from  the  urine  of  man 
are,  however,  great,  and  it  is  therefore  advisable  that  the  stu- 
dent should  learn  to  isolate  this  substance  when  it  is  present  in 
larger  quantities  than  normal  in  the  urine.  As  the  urine  of 
herbivora  contains  large  quantities  of  hippuric  acid,  it  may  be 
advantageous  to  use  for  the  experiment  to  be  described  cows' 
or  horses'  urine,  or  the  urine  of  men  in  whom  an  excessive 
excretion  of  hippuric  acid  has  been  induced  ;  this  may  be  done 
by  administering  to  a  man  ten  or  fifteen  grammes  of  benzoic 
acid  ten  or  twelve  hours  before  the  urine  is  collected. 

It  is  a  fact  worthy  of  remembrance  that  when  benzoic  acid  is 
administered  to  healthy  men,  large  quantities  of  hippuric  (ghy- 
co-benzoic)  acid  are  excreted.  There  appears  to  be  always  in 
the  system  a  quantity  of  glycocine  (C.^H.,  (NH2)  OJ.  which  al- 
though it  is  never  excreted  as  such,  is  capable  of  being  seized 
upon  by  the  radical  of  benzoic  acid,  so  as  to  yield  hippuric  acid. 
By  comparing  the  formula?  of  glycocine  and  hippuric  acid,  ex- 
hibited below,  it  will  be  seen  that  the  latter  can  be  represented 
as  derived  from  the  former  by  the  substitution  of  (C7ILO)  for 
II,  thus:— 

Glycocine 02H,(NHB)Os 

Hippuric  acid C,II,(NIIJ (C.II50)0,. 

Take  200  cubic  centimetres  of  the  fresh  urine  of  the  cow 
and  concentrate  it,  by  beating  an  the  water-bath,  to  forty  cubic 


538  THE   SECRETIONS. 

centimetres.  Then  add  hydrochloric  ;ici<l,  and  set  aside  until 
next  day.  A  large  quantity  of  hippuric  acid  will  have  separa- 
ted in  the  form  of  a  brown  crystalline  mass.  Wash  with  cold 
water,  press  the  crystalline  mass  between  folds  of  filtering 
paper;  dissolve  in  as  little  boiling  water  as  possible,  add  a 
little  pure  animal  charcoal  (i.  p.,  animal  charcoal  which  has 
been  in  contact  with  dilute  hydrochloric  acid  for  many  days, 
and  then  thoroughly  washed  with  water),  and  filter.  The 
filtrate  should  be  concentrated  and  allowed  to  crystallize. 
(For  other  methods  of  separating  hippuric  aeid,  especially 
when  existing  in  small  quantities,  the  reader  is  referred  to 
Hoppe-Seyler's  "  Handbuch  der  physiologisch-  und  patholo- 
gisch-chemischen  Analyse,  1870,  p.  157). 

Having  obtained  nearly  pure  hippuric  acid,  the  following 
experiments  may  be  tried  : — 

1.  Dissolve  a  fragment  in  boiling  water,  and  allow  a  drop 
of  the  solution  to  crystallize  on  a  microscope  slide.  The  acid 
usually  separates  in  the  form  of  transparent  prisms  which  are 
single,  or  occur  in  radiating  groups,  and  generally  present  four 
sides  parallel  to  their  long  axis  ;  their  ends  are  terminated  by 
two  or  four  planes.  Their  primary  form  is  a  right  rhombic 
prism  (fig.  313). 

2.  Heat  a  fragment  of  hippuric  acid  in  a  small  glass  tube, 
with  a  little  soda-lime  ;  the  ammonia  which  is  given  off,  and 
which  can  readily  be  detected  by  its  odor,  proves  that  the  body 
under  examination  contains  nitrogen. 

3.  Mix  a  fragment  of  hippuric  acid  with  strong  nitric  acid 
in  a  small  porcelain  crucible.  Boil  and  then  evaporate  to 
dryness;  on  heating  the  residue,  a  very  characteristic  odor  of 
nitro-benzol  is  developed. 

*  188.  Separation  of  Creatinine  (C4H7NsO)  from 
Urine. — To  300  cubic  centimetres  of  urine  add  milk  of  lime 
until  the  reaction  of  the  fluid  is  decidedly  alkaline.  Then  add 
a  solution  of  chloride  of  calcium  as  long  as  a  precipitate  falls. 
After  the  precipitate  has  been  allowed  partially  to  subside, 
filter,  evaporate  the  filtrate  to  dryness  in  a  basin  or  the  water- 
bath,  and  add  to  the  yet  warm  residue  thirty  or  forty  cubic 
centimetres  of  95  per  cent,  alcohol.  Stir  and  decant  the  con- 
tents of  the  basin  into  a  beaker,  taking  care  to  add  the  alco- 
holic washings  of  the  basin.  Set  aside  the  beaker  in  a  cool 
place.  Filter  and  wash  the  insoluble  residue  with  a  little  more 
spirit.  If  the  filtrate  and  washings  amount  to  more  than  50 
c.  c,  concentrate  at  a  gentle  heat  to  that  volume.  Allow  the 
fluid  to  cool,  and  then  add  half  a  cubic  centimetre  of  an  alco- 
holic solution  of  chloride  of  zinc,  absolutely  free  from  the  least 
trace  of  acid,  and  stir  for  some  time.  Set  the  beaker  aside  for 
three  or  four  days  in  a  cellar.  At  the  end  of  that  time  the 
whole  of   the  creatinine  will  have  separated  in  combination 


BY    DR.    LAUDER    BRUNTON.  539 

with  zinc  chloride.  It  should  be  collected  on  a  filter  and 
washed  with  pure  spirit;  the  substance  left  on  the  filter  con- 
sists of  chemically  pure  chloride  of  zinc-creatinine  (C4H7N30).2, 
ZnCl„.  This  most  characteristic  compound  is  very  slightly 
soluble  in  cold  water  and  insoluble  in  cold  alcohol ;  it  crystal- 
lizes from  urine  in  the  form  of  bundles  of  needles. 

From  chloride  of  zinc-creatinine,  the  pure  substance  is 
obtained  by  boiling  with  freshly  pi'epared  and  thoroughly 
washed  h}rdrate  oxide  of  lead  for  half  an  hour  or  longer.  On 
filtering  the  fluid,  and  evaporating  to  dryness,  creatinine  is 
obtained,  which  may  be  dissolved  in  alcohol  and  crystallized. 

Creatinine  is  very  soluble  in  cold  alcohol.  The  following 
experiments  may  be  performed  with  it : — 

1.  When  a  few  drops  of  a  solution  are  allowed  to  evaporate 
spontaneously,  colorless  prisms  are  obtained  (fig.  302). 

2.  The  taste  of  the  solution  is  strongly  alkaline. 

3.  The  reaction  to  test-paper  is  intensely  alkaline. 

4.  A  concentrated  solution  of  chloride  of  zinc  added  to 
creatinine,  causes  the  immediate  precipitation  of  the  zinc  com- 
pound, which  is  always  crystalline. 

**  189.  Separation  of  the  Coloring  matters  of 
Urine. — Under  various  names,  among  others  that  of  Urohae- 
matine,  different  writers  have  described  the  substance,  or 
mixture  of  substances,  which  they  considered  to  be  the  cause 
of  the  color  of  healthy  urine  (Scherer,  Harle}7,  Heller).  We 
are  now  perfectly  convinced  that  no  one  coloring  matter,  capa- 
ble of  accounting  for  the  normal,  golden,  or  amber  color  of 
human  mine,  has  been  separated. 

The  following  experiments  maybe  performed,  as  they  throw 
some  light  on  the  reactions  of  the  normal  urinary  coloring 
matter : —  » 

1.  Take  200  cubic  centimetres  of  urine  and  precipitate  with 
neutral  acetate  of  lead  ;  an  abundant  precipitate  falls,  which 
consists  of  lead  salts  of  acids  present  in  the  urine,  and  which 
contains  a  portion  of  the  urinary  coloring  matter.  Filter,  and 
observe  that  the  filtrate  from  this  precipitate  is  not  altogether 
colorless.  Add  to  the  filtrate  basic  acetate  of  lead,  when  a 
further  precipitate  will  form,  which,  when  separated,  leaves  a 
colorless  filtrate. 

Now  unite  the  precipitates  caused  by  neutral  and  basic 
acetates  of  lead,  and  treat  the  mixture  with  alcohol  acidulated 
with  hydrochloric  acid.  A  red  fluid  will  be  obtained,  which, 
on  filtration  and  evaporation,  yields  a  reddish-black  residue, 
insoluble  in  water. 

That  this  is  not,  as  was  supposed,  the  coloring  matter  of 
urine,  is  now  admitted.  The  researches  of  Dr.  Harley,  although 
failing  to  discover  any  one  normal  urinary  coloring  matter,  show 


540  TI1K    SKCRKTIONS. 

that  the  so-called  urohiematinc  contains  a  mixture  of  several 
pigmentary  substances. 

2.  Passing  from  urohrcmatine,  the  student's  attention  is  to 
be  drawn  to  the  constant  presence  in  urine  of  a  very  well- 
defined  body — viz.,  indican,  or  white  indigo  (C,8H12N,0,) — 
which  may  readily  be  converted  into  indigo-blue  and  indigo- 
red.  To  the  indican  present  in  urine,  Heller,  who  first  dis- 
covered its  presence,  without,  however,  being  aware  of  its 
nature,  gave  the  name  of  Uroxanthine,  and  to  the  indigo-blue 
and  indigo-red  obtained  from  it,  the  names  of  Uroglaucine  and 
Urrhodin  respectively. 

For  the  method  of  obtaining  indican,  the  reader  is  referred 
to  Hoppe-Seyler  (op.  cit.  p.  163) ;  it  will  be  sufficient  if  the 
student  performs  the  following  experiments: — 

Precipitate  100  cubic  centimetres  of  perfectly  fresh  urine 
with  acetate  of  lead.  The  fluid  is  filtered.  The  filtrate  con- 
tains the  whole  of  the  indican.  A  strong  solution  of  ammonia 
is  added,  which  precipitates  hydrated  lead  oxide,  together 
with  indican.  The  precipitate  is  collected  on  a  filter,  washed 
with  water  and  dilute  dydrochloric  acid.  Very  often  the 
filter  is  seen  to  contain  blue  particles,  in  consequence  of  the 
production  of  indigo-blue,  which  contrasts  with  the  chloride  of 
lead  with  which  it  is  mixed. 

The  filtrate,  when  left  to  itself  for  twenty -four  hours,  gener- 
ally becomes  covered  with  a  bluish-purple  film,  consisting  of 
indigo. 

3.  Several  hundred  cubic  centimetres  of  pure  urine  are  pre- 
cipitated by  acetate  of  lead  and  then  filtered ;  the  filtrate  is 
treated  with  excess  of  sulphuretted  hydrogen,  boiled  and 
filtered;  the  filtrate  is  now  poured  into  an  equal  volume  of 
pure  and  strong  hydrochloric  acid.  The  fluid  becomes  either 
violet  or  indigo-blue  ;  it  is  allowed  to  stand  for  twelve  hours, 
and  diluted  with  an  equal  volume  of  water.  After  about 
twenty-four  hours,  a  deposit  will  generally  have  formed,  which 
is  collected  on  a  filter,  washed,  and  dried.  When  treated  witli 
ether,  the  deposit  will  generally  yield  to  it  a  red  coloring 
matter,  whilst  indigo  is  left  behind,  and  is  to  be  purified  by 
solution  in  boiling  alcohol. 

The  student  will  remember  that  indigo-blue  only  differs  from 
indican  in  the  possession  of  two  additional  atoms  of  hydro- 
gen,— 

Indican,  or  white  indigo ClfH].iN.!0.!. 

Indigotin,  or  blue  indigo C^II^N.^O.^. 

In  the  production  of  indigo-blue  from  indican  there  are 
other  substances  formed,  such  as  a  form  of  sugar,  which  is  an 
isomer  of  glucose,  but    unfermentable,  and  the   imperfectly 


BY   DR.    LAUDER    BRUNTON.  541 

investigated  body,  indigo-red,  which  has  already  been  alluded 
to.1 

The  following  reactions  may  be  tried  with  indigo-blue : — 

(a)  Shake  a  fragment  of  indigo-blue  with  ether ;  the  sub- 
stance is  found  to  be  veiy  scantilj7  soluble.  Ether,  however, 
dissolves  enough  to  acquire  a  faint  blue  tint. 

(b)  Place  a  fragment  in  a  narrow  glass  tube  and  heat ;  it 
will  sublime  and  be  deposited  in  the  cool  part  of  the  tube.  If 
the  latter  be  very  narrow  and  thin,  it  may  be  examined 
microscopically.  The  sublimate  of  indigo  is  then  seen  to  con- 
sist of  microscopic  needles  and  plates. 

Methods  fok  the  Quantitative  Analysis  op  Urine. 

**  190.  Determination  of  the  total  quantity  of  Urine 
passed  in  a  given  time. — Before  describing  briefly  the 
methods  which  are  employed  for  the  determination  of  the  more 
important  urinary  constituents,  attention  must  be  drawn  to 
the  fact  that,  as  a  general  rule,  quantitative  analj'sis  of  urine 
throws  little  or  no  light  on  the  rate  and  character  of  the  tis- 
sue changes  going  on  in  the  animal  body,  unless  the  analysis 
be  made  of  a  specimen  of  urine  which  represents  the  average 
excretion  of  a  known  period,  during  which  the  conditions  of 
the  animal  have  been  ascertained  as  accurately  as  possible. 

These  remarks  will  be  better  understood  when  it  is  stated 
that  we  can  obtain  the  most  valuable  information  relating  to 
the  urinary  secretion  if  we  collect,  mix,  and  then  measure  the 
whole  of  the  urine  passed  in  twenty-four  hours.  Having 
ascertained  the  total  volume  of  urine  passed  in  twenty-four 
hours,  two  hundred  cubic  centimetres  will  suffice  for  the  great 
majority  of  quantitative  analyses. 

The  urine  of  man  must  be  collected  in  perfectly  clean  glass 
vessels  which  in  accurate  experiments,  should,  before  being 
used,  be  washed  with  dilute  sulphuric  acid,  and  then  with 
water.  The  collecting-vessel  ma}'  be  graduated  or  not ;  in  the 
latter  case,  the  urine  is  carefully  poured,  if  necessary,  in  suc- 
cessive portions,  after  being  mixed,  into  a  cylinder  capable  of 
holding  a  litre  of  water,  and  divided  into  200  parts;  so  that 
each  division  indicates  5  cubic  centimetres. 

It  is  frequently  of  use  to  collect  the  urine  of  dogs  and  rab- 
bits, especially  when  experiments  are  made  on  the  physiological 
action  of  drugs. 

1  In  many  cases  of  disease,  urine  contains  so  much  indican,  that  the 
following  reaction  may  be  observed  : — 

To  five  cubic  centimetres  of  fuming  hydrochloric  acid,  add  from  one 
to  two  cubic  centimetres  of  urine.  A  violet  color  is  produced,  which 
passes  into  red. 


542  THE   SECRETIONS. 

In  those  cases,  cages  are  employed,  whose  walls  are  made 
partly  of  sheet  iron  or  zinc,  and  partly  of  wire  netting.  The 
floor  of  the  cage  should  he  made  of  thick  glass  rods  (about 
four-tenths  of  an  inch  in  diameter),  placed  very  closely  together. 
These  rods  are  so  arranged  that  the  spaces  between  them  will 
allow  urine  to  trickle  away,  whilst  the  solid  excreta  are  re- 
tained. 

The  glass  rods  are  firmly  inserted  into  the  wooden  base  of 
the  cage  ;  this  is  furnished  with  a  drawer,  into  which  is  accu- 
rately fitted  a  flat  glass  or  porcelain  dish,  such  as  is  used  by 
photographers  in  washing  photographs.  The  dish  is  perforated 
by  a  hole,  in  which  a  tube  (preferably  of  glass)  is  accurately 
fitted,  and  leads  to  the  collecting  vessels  outside. 

If  care  be  taken  to  wash  the  glass-rod  bottom  of  the  cage 
and  the  collecting-glass  dish  placed  beneath  it,  the  urine  may 
be  collected  in  a  state  of  great  purity. 

**  191.  Determination  of  the  specific  gravity  of 
Urine. — This  may  be  effected  in  either  of  the  two  ways  de- 
scribed in  App.  §  216,  for  the  determination  of  the  specific 
gravity  of  fluids,  viz.,  by  means  of  a  hydrometer  or  with  the 
specific  gravity  bottle. 

The  hydrometer  employed  for  taking  the  specific  gravity  of 
urine  is  called  a  urinometer ;  in  this  country  its  stem  is  usually 
divided  so  as  to  indicate  densities  ranging  from  1000  to  1060 
(water  being  1000) ;  it  is  preferable  to  use  two  urinometers  : 
one  indicating  densities  from  1000  to  1030,  the  other  from 
1030  to  1060.  The  length  of  the  stem  being  the  same  as  that 
of  the  ordinary  instruments,  the  accuracy  of  the  reading  will 
be  much  increased.  Before  using  a  urinometer,  its  accuracy 
should  be  checked  by  immersing  it  in  fluids  of  known  specific 
gravity.  If  the  specific  gravity  of  three  samples  of  urine  be 
accurately  taken  with  the  bottle,  data  are  obtained  for  checking 
the  accuracy  of  the  urinometer. 

Although,  under  certain  circumstances,  important  informa- 
tion may  be  obtained  by  a  determination  of  the  specific  gravity 
of  an  isolated  sample  of  urine,  generally  it  is  only  when  the 
specific  gravity  of  a  sample  of  the  mixed  and  measured  urine 
of  the  twenty-four  hours  is  ascertained,  that  we  learn  much 
from  the  experiment. 

A  knowledge  of  the  specific  gravity  enables  one  to  form  a 
near  approximation  to  the  total  quantity  of  solid  matter  ex- 
creted by  the  kidneys  in  a  given  time. 

It  has  been  empirically  determined  that  the  specific  gravity 
of  urine  generally  bears  a  close  relation  to  the  solid  matters 
which  it  contains  in  solution.  Sir  Robert  Christison  pointed 
out,  many  years  ago,  that  if  the  whole  numbers  which  express 
the  difference  between  the  density  of  a  sample  of  urine  and  the 
density  of  water  (expressed  as  1000)  be  multiplied  by  the  factor 


BY    DR.    LAUDER    BRUNTON.  543 

2.33,  the  product  represents  very  closely  the  weight  of  the 
total  solids  contained  in  1000  parts,  by  weight,  of  urine. 
Subsequent  observers  have  determined  that  whilst  Christison's 
formula  yields  very  correct  results  when  applied  to  urines  of 
specific  gravities  above  1018,  for  urines  of  lower  specific  gravity 
greater  accuracy  is  obtained  by  substituting  the  factor  -2  for 
2.33. 

The  following  example  will  suffice  to  show  the  method  of 
calculating  approximately  the  total  solid  matter  excreted  in 
the  urine  in  twentjT-four  hours  : — 

A  man  passes  in  twenty-four  hours  1575  cubic  centimetres 
of  urine  of  specific  gravity  1023,  and  it  is  desired  to  obtain  an 
approximate  estimate  of  the  total  urinary  solids. 

1st.  We  find  the  total  solids  (expressed  in  any  particular 
units  of  weight)  contained  in  1000  par,ts  (expressed  in  the 
same  units  of  weight)  by  Dr.  Christison's  formula,  thus,  if  the 
unit  be  the  gramme,  and  the  quantity  of  solid  matter  in  1000 
grammes  be  represented  by  x, 

x  =  (1023  —  1000)  2.33  =  53.59. 

2d.  We  require  to  know  the  weight  of  the  whole  of  urine. 
As  its  density  is  1023,  and  the  quantity  1576  cubic  centimetres, 
the  weight  in  grammes  is  at  once  found  by  the  following 
proportion : — 

1000  :  1023  ::  1575  :  x 

x  =  1023x  1575  =  16n> 

1000 

3d.  Knowing  the  weight  in  grammes  of  the  urine  of  twenty- 
four  hours,  and  the  approximate  weight  of  total  solid  matters 
in  1000  parts,  by  weight,  of  urine,  we  obtain  the  total  solids 
passed  in  twenty-four  hours  expressed  in  grammes: — 

1000  :  53.59  ::  1611  :  x 
x  =  86.33  grammes. 

It  is  to  be  noted  that  the  result  obtained  by  such  calcula- 
tions is  merety  an  approximation  to  the  actual  number  which 
would  be  ascertained  by  the  direct  method,  to  be  immediately 
described  ;  the  approximation  is,  however,  sufficiently  close  to 
be  useful. 

192.  Determination  of  the  Total  Solid  Matters  con- 
tained in  Urine. — If  we  know  the  total  volume  of  urine 
passed  in  twenty-four  hours,  and  it  be  desired  to  ascertain,  by 
direct  weighing,  the  total  quantity  of  solid  matter  contained 
in  it,  10  or  15  cubic  centimetres  of  the  mixed  urine  are  poured 
from  a  very  accurately  graduated  pipette  into  a  weighed  porce- 
lain or  glass  capsule,  which   is  heated   over  the  water-bath, 


544  THE   SECRETIONS. 

or  in  the  water  oven  (fig.  :{:!!>),  until  a  nearly  dry  residue  is 
obtained.  The  capsule  with  its  contents  is  then  heated  in  an 
air  oven  whose  temperature  is  maintained  at  120°  C.  The 
capsule  is,  after  some  time,  allowed  to  cool  in  an  exsiccator 
(fig.  340)  and  rapidly  weighed.  The  drying  and  weighing 
should  be  repeated  until  the  weight  of  the  capsule  and  residue 
is  constant.  In  order  to  secure  accuracy,  the  capsule  in  which 
the  evaporation  is  carried  on  should  be  fitted  with  a  ground 
glass  plate,  which  should  be  placed  over  it,  when  it  is  trans- 
ferred from  the  air  oven  to  the  exsiccator,  and  from  the  ex- 
siccator to  the  balance. 

It  is  absolutely  essential  that  the  weighing  should  be  con- 
ducted with  the  greatest  possible  rapidity,  as  the  dried  urinary 
solids  are  highly  hygroscopic. 

Instead  of  measuring  the  urine  used  in  the  analysis,  a 
weighed  quantity  may  be  taken. 

**  193.  Determination  of  the  Amount  of  Chlorine 
contained  in  Urine. 

By  Liebig's  Method — It  has  been  already  mentioned  that 
when  a  solution  of  mercuric  nitrate  is  added  to  a  solution  of 
urea,  a  dense  white  precipitate  is  formed,  which  consists  of 
compounds  of  urea  with  mercuric  oxide. 

If  the  solution  of  mercuric  nitrate  be  sufficiently  diluted, 
and  be  added  in  sufficient  quantity,  the  compound  formed  con- 
tains four  molecules  of  mercuric  oxide  for  each  molecule  of 
urea. 

If,  however,  a  solution  of  mercuric  nitrate  be  added  to  a 
solution  of  urea  and  chloride  of  sodium,  no  precipitate  will  at 
first  be  formed,  the  reaction  between  the  urea  and  oxide  of 
mercury  not  occurring  until  the  double  decomposition  between 
the  mercuric  nitrate  and  sodium  chloride  has  been  completed, 
thus: — 

Hg  2N03  +  2NaCl=Hg  Cl,+ 2NaN03. 

As  soon,  however,  as  this  has  occurred,  a  white  precipitate 
of  the  mercuric  oxide  and  urea  compound  falls. 

Liebig's  method  of  determining  the  amount  of  chlorine  in 
urine  is  based  upon  the  reactions  which  have  been  referred  to. 

In  order  to  enable  the  student  to  determine  the  amount  of 
chlorine  by  Liebig's  method,  we  shall  describe,  in  the  first 
place,  the  method  of  preparing  the  standard  solution  of  nitrate 
of  mercury,  and,  in  the  second  place,  the  method  to  be  fol- 
lowed in  determining  by  its  aid  the  quantity  of  chlorine  in 
urine. 

Preparation  of  standard  solution  of  mercuric  nitrate  for 
the  estimation  of  chlorine  in  Urine. 

The  following  solutions  are  required  : — 

1st.  A  solution  of  mercuric  nitrate  of  such  a  strensth  that 


BY    DR.    LAUDER    BRUNTON.  545 

one   cubic   centimetre   shall   correspond  to   10   milligrammes 
(0.010  grm.)  of  sodium  chloride. 

This  solution  may  be  made  by  dissolving  twenty  grammes 
of  perfectly  pure  metallic  mercury  in  boiling  nitric  acid,  until 
a  drop  of  the  acid  fluid  does  not  cause  a  precipitate  when  added 
to  a  solution  of  common  salt.  The  acid  fluid  is  concentrated 
by  heating  over  a  water-bath  until  it  is  of  syrupy  consistence. 
It  is  then  diluted  with  nearly  a  litre  of  distilled  water. 

Unless  a  great  excess  of  nitric  acid  has  remained  after  the 
evaporation,  a  white  precipitate,  consisting  of  a  basic  nitrate 
of  mercury,  will  fall,  and  must  be  separated  by  filtration.  Be- 
fore performing  the  latter  operation,  a  few  drops  of  nitric  acid 
may,  however,  be  added,  as  they  will  cause  the  re-solution  of  a 
considerable  part  of  the  precipitate,  without  rendering  the 
liquid  too  acid.  The  solution  of  mercuric  nitrate  thus  made 
must  be  set  aside  until  the  other  reagents  which  are  required 
for  determining  its  strength  are  prepared. 

2d.  A  solution  made  by  dissolving  in  distilled  water  20 
grammes  of  pure  sodium  cloride  and  diluting  to  one  litre.  The 
salt  is  fused  before  being  weighed. 

Ten  cubic  centimetres  of  this  solution  contain  0.200  grm.  of 
NaCl. 

3d.  A  solution  made  by  dissolving  4  grammes  of  pure  urea 
in  distilled  water  and  diluting  to  100  c. c. 

4th.  A  solution  of  sodium  sulphate,  saturated  at  ordinary 
temperatures. 

In  order  to  determine  the  strength  of  the  solution  of  mer- 
curic nitrate,  it  is  poured  into  a  burette  (preferably  a  Mohr's 
burette,  with  glass  stopcock)  of  a  capacity  of  50  cubic  centi- 
metres, and  divided  into  lOths  of  a  cubic  centimetre. 

Ten  cubic  centimetres  of  the  standard  solution  of  chloride 
of  sodium  are  then  measured  by  means  of  a  pipette,  and  poured 
into  a  glass  beaker. 

To  this  is  added  3  cubic  centimetres  of  the  solution  of  urea, 
and  5  cubic  centimetres  of  the  solution  of  sulphate  of  sodium. 
The  solution  of  nitrate  of  mercury  is  now  allowed  to  flow 
gently  into  the  beaker;  as  the  drops  fall  into  the  fluid  con- 
tained in  the  latter,  a  white  precipitate  is  seen  to  form,  which, 
however,  dissolves  at  once,  or  when  the  fluid  is  stirred.  On 
adding  more  of  the  solution  of  nitrate  of  mercury,  the  fluid 
becomes  opalescent  but  no  precipitate  occurs  until  the  reaction 
is  completed,  i. e.,  until  the  whole  of  the  chloride  of  sodium 
has  been  decomposed. 

The  number  of  cubic  centimetres  of  the  solution  of  mercuric 
nitrate  which  has  been  added  is  read  off;  if,  for  example,  12.7 
cubic  centimetres  of  the  solution  had  to  be  added  in  order  to 
induce  a  permanent  precipitate,  we  conclude  that  this  quantity 
of  solution  contains  the  quantity  of  mercuric  nitrate  required 
35 


546  THE    SECRETIONS. 

to  decompose  0.200  gramme  of  NaCl.  As  it  is  convenient  to 
have  a  solution  of  which  10  cubic  centimetres  shall  be  equiva- 
lent to  0.100  gramme  of  NaCl,  we  must  take  our  solution  and 
dilute  it  to  the  required  extent.  In  the  assumed  case,  12.7 
cubic  centimetres  contained  as  much  of  the  mercurial  salt  as 
correspond  to  0.200  gramme  of  NaCl,  i.  e.,  as  much  as  would 
be  required  in  20  cubic  centimetres  of  solution.  If  we  there- 
fore diluted  12.7  cubic  centimetres  with  7.3  cubic  centimetres 
of  water,  we  should  obtain  20  cubic  centimetres  of  a  solution 
of  which  10  cubic  centimetres  would  be  exactly  capable  of  de- 
composing 0.100  gramme  of  NaCl. 

But  as  in  preparing  such  a  standard  solution  we  deal  with 
large  quantities  of  fluid,  it  is  well  to  effect  the  dilution  of  the 
whole  at  once. 

Thus  let  us  suppose  that  we  have  800  cubic  centimetres  of 
the  solution,  of  which  12.7  cubic  centimetres  are  equivalent  to 
0.200  gramme  of  NaCl. 

As  12.7  cubic  centimetres  require  the  addition  of  7.3  cubic 
centimetres  of  water,  it  is  easy  to  find  how  much  800  cubic 
centimetres  require,  viz.,  459.8  cubic  centimetres.  If  we  then 
measure  out  very  accurately  this  quantity  of  distilled  water, 
and  add  it  to  our  solution,  we  obtain  1259.8  cubic  centimetres 
of  a  solution  of  which  10  cubic  centimetres  represent  100  milli- 
grammes of  NaCl,  or  60.65  milligrammes  of  CI. 

Having  made  the  standard  solution  of  nitrate  of  mercury 
for  the  estimation  of  chlorine,  we  must,  before  analyzing  urine, 
prepare  a  solution  which  we  shall  designate  as  Baryta  Mixture. 

This  is  prepared  by  mixing  two  volumes  of  a  solution  of 
barium  nitrate,  saturated  in  the  cold,  with  one  volume  of  a 
solution  of  caustic  baryta  (barium  hydrate),  similarly  saturated. 

Two  volumes  of  the  urine  to  be  analyzed  (say  40  cubic  centi- 
metres) are  now  mixed  with  one  volume  (say  20  cubic  centi- 
metres) of  baryta  mixture.  An  abundant  precipitate  falls, 
consisting  chiefly  of  a  mixture  of  phosphate,  sulphate,  and  car- 
bonate of  barium.  (This  removal  of  phosphates  is  essential, 
as  these  salts  are  precipitated  by  the  solution  of  nitrate  of 
mercury.) 

The  fluid  in  which  the  precipitate  has  formed  is  filtered,  care 
being  taken  that  the  filter  is  not  moistened. 

As  the  filtrate  contains  one-third  of  its  volume  of  baryta 
mixture,  it  is  convenient  to  take  for  analysis  15  cubic  centi- 
metres. This  quantity  will  exactly  correspond  to  10  cubic  cen- 
timetres of  urine.  It  is  convenient,  therefore,  to  have,  in  addi- 
tion to  pipettes  graduated  so  as  to  deliver  20  and  40  cubic 
centimetres,  one  which  delivers  exactly  15  cubic  centimetres 
of  fluid.  The  measured  portion  of  filtrate  is  very  slightly 
acidified  by  adding,  drop  by  drop,  exceedingly  dilute  nitric 
acid,  and  then  the  solution  of  nitrate  of  mercury  is  allowed  to 


BY    DR.    LAUDER    BRUNTON.  547 

flow  in,  at  first  rather  rapidly,  afterwards  guttatim,  until  a  per- 
manent and  dense  cloud,  not  affected  by  vigorous  stirring, 
makes  its  appearance. 

The  number  of  cubic  centimetres  used,  multiplied  by  0.010. 
indicates  the  amount  of  chlorine,  in  fractions  of  a  gramme,  cal- 
culated as  NaCl,  contained  in  10  cubic  centimetres  of  urine. 
Thus,  if  8.56  cubic  centimetres  of  the  standard  solution  of 
chlorine  were  added,  the  quantity  of  CI,  calculated  as  NaCl, 
in  10  cubic  centimetres,  would  be  0.085  gramme. 

It  must  be  remarked  that  if  a  urine  contains  albumin,  this 
substance  must  be  removed  by  boiling  and  filtration  before  the 
determination  of  chlorine  bjr  Liebig's  method  can  be  effected. 

194.  Determination  of  chlorine  by  means  of  nitrate  of  silver. 
— In  cases  where  the  quantity  of  chlorine  is  exceedingly  small, 
the  following  method  is  much  to  be  preferred  to  that  already 
described. 

Ten  cubic  centimeti'es  of  urine  are  placed  in  a  platinum  cap- 
sule, together  with  2  grammes  of  pure  potassium  nitrate  (quite 
free  from  chlorine),  and  evaporated  to  dryness.  The  residue  is 
ignited  at  a  moderate  heat  until  the  whole  of  the  carbon  has 
disappeared. 

The  crucible  is  allowed  to  cool,  and  the  saline  mass  which  it 
contains  is  dissolved  in  distilled  water,  a  little  nitric  acid  being 
added.  The  estimation  of  chlorine  may  then  be  effected  by 
those  methods  which  are  to  be  found  described  in  text-books 
on  chemical  analysis.  The  chief  of  these  methods  consist  (a) 
in  precipitating  the  chlorine  as  chloride  of  silver,  etc.,  washing, 
burning,  and  weighing  the  precipitate;  and  (6)  in  adding  to 
the  neutralized  solution  of  the  chloride,  mixed  with  a  drop  of 
potassium  chromate,  a  standard  solution  of  nitrate  of  silver. 
Thfr  nitrate  of  silver  causes  a  white  precipitate  of  chloride  of 
silver,  when  added  to  such  a  solution,  until  the  whole  of  the 
chlorine  has  been  precipitated.  Then,  however,  the  addition 
of  a  single  drop  more  produces  a  deep  salmon-red  color,  due 
to  the  formation  of  silver  chromate. 

**  195.  Determination  of  the  amount  of  Urea  found 
in  Urine. 

I.  By  Liebig's  Method In  order  to  determine  the  amount  of 

urea  by  Liebig's  method,  we  require  (a)  baryta  mixture  as  used 
in  the  determination  of  the  amount  of  CI  in  urine,  and  (b)  a 
standard  solution  of  nitrate  of  mercury,  prepared  in  the  same 
manner  as  that  used  for  CI  determinations,  but  containing 
much  more  mercury.  In  making  this  solution,  dissolve  about 
75  grammes  of  pure  mercury  in  pure  nitric  acid,  adopting  all 
the  precautions  previously  suggested,  and  dilute  to  the  volume 
of  oik;  litre. 

In  order  to  grade  the  solution  of  mercuric  nitrate  for  uren, 
we  must  pour  into  a  beaker  10  cubic  centimetres  of  a  standard 


548  THE    SECRETIONS. 

aqueous  solution  of  pure  urea,  containing  2  grammes  of  per- 
fectly  pure  urea  in  100  cubic  centimetres.  The  quantity  of  so- 
lution in  the  beaker  will  then  contain  0/200  gramme  of  urea. 

The  solution  of  mercuric  nitrate  is  then  added  and  the  fluid 
stirred  ;  an  abundant  snow-white  precipitate  falls.  When  the 
precipitation  appears  to  be  nearly  completed,  a  drop  of  the  fluid 
holding  the  precipitate  in  suspension  is  added  to  a  drop  of 
solution  of  sodium  carbonate  on  a  porcelain  slab.  If  the  urea 
be  not  completely  precipitated,  no  change  of  color  will  be  ob- 
served when  the  two  fluids  are  mixed.  The  mercuric  nitrate 
solution  is  then  added  drop  by  drop,  and  the  process  of  testing 
with  the  solution  of  Na^CO.,  on  the  slab  repeated  from  time  to 
time.  At  last  a  3rellow  color  will  appear.  This  will  indicate 
that  the  solution  of  mercury  has  been  added  in  excess.  The 
number  of  cubic  centimetres  of  solution  added  indicates  the 
number  of  c.  c.  which  are  equivalent  to  0.200  gramme  of  urea. 
As  it  is  convenient  to  have  a  solution  of  mercuric  nitrate,  of 
wdiich  10  cubic  centimetres  shall  precipitate  100  milligrammes 
of  urea  (0.100),  or  1  cubic  centimetre  10  milligrammes,  it  is 
essential  to  dilute  the  solution  which  has  been  prepared,  in  the 
same  manner  as  was  indicated  in  the  case  of  the  solution  for 
the  determination  of  chlorine. 

Having  prepared  the  solution  of  mercuric  nitrate  for  urea, 
and  the  baryta  mixture,  the  analysis  of  urine  can  be  rapidly 
effected.  40  cubic  centimetres  of  urine  are  mixed  with  20  cubic 
centimetres  of  baryta  mixture;  15  cubic  centimetres  of  the  fil- 
trate are  precipitated  with  the  mercury  solution,  until  a  yellow 
reaction  with  solution  of  Na2C03  is  obtained. 

The  number  of  cubic  centimetres  of  the  mercury  solution 
used,  minus  2  and  multiplied  by  0.010  gramme,  indicates  very 
closely  the  amount  of  urea,  expressed  in  fractions  of  a  gramme, 
contained  in  10  cubic  centimetres  of  urine,  provided  that  the 
urine  be  of  average  composition,  i.  e.,  that  it  contains  no  ab- 
normal substances,  that  the  amount  of  chlorine  in  it  be  about 
the  average,  and  that  it  be  neither  very  concentrated  nor  very 
dilute. 

The  statements  made  in  the  preceding  paragraph  indicate 
many  circumstances  which  have  to  be  taken  into  account,  and 
many  corrections  which  have  to  be  introduced  in  order  to  give 
to  Liebig's  method  the  accuracy  of  which  it  is  capable. 

In  pointing  out  these  corrections,  an  explanation  must  be 
given  of  the  empirical  statement,  '■'•that  the  number  of  cubic 
centimetres  of  mercury  solution  used,  minus  2,  and  multiplied 
by  0.01  grm.,  indicates  very  closely  the  amount  of  urea,  ex- 
pressed in  fractions  of  a  gramme,  contained  in  10  cubic  centi- 
metres of  urine."  The  reason  for  subtracting  2  cubic  centi- 
metres is,  that  in  average  urines  this  volume  of  the  solution  is 


BY    DR.    LAUDER    BRTJNTON.  549 

required  to  decompose  the  chlorides,  and  does  not,  therefore, 
take  part  in  the  urea  reaction. 

If  this  correction  be  constantly  introduced  in  a  series  of  ob- 
servations, and,  as  has  been  ahead}7,  pointed  out,  the  urine  be 
not  of  very  exceptional  composition,  results  are  obtained  which 
are  very  nearly  correct,  and  which  are  comparable  the  one  with 
the  other.  If,  however,  the  urine  in  cases  of  pneumonia  or  of 
fevers  were  under  investigation,  the  error  introduced  by  the 
application  of  this  arbitrary  correction  would  generally  be  very 
great. 

In  such  cases  we  must  adopt  a  more  scientific  method  of 
avoiding  the  error  introduced  by  the  presence  of  chlorides.  We 
must  in  the  first  place  determine,  by  the  standard  solution  of 
mercuric  nitrate  for  chlorine,  the  amount  of  chlorine,  calcu- 
lated as  NaCl  present  in  10  cubic  centimetres  of  the  urine,  i.e., 
in  15  cubic  centimetres  of  the  filtrate  obtained  on  mixing  two 
volumes  of  urine  with  one  volume  of  baryta  mixture,  and  we 
must  then  remove  the  whole  of  the  CI  from  a  fresh  quantity 
of  filtrate  by  a  standard  solution  of  nitrate  of  silver.  To  do 
this  we  require  a  solution  of  nitrate  of  silver  exactly  equivalent 
to  the  solution  of  nitrate  of  mercury  Which  has  been  used.  If 
11.601  grammes  of  fused  silver  nitrate  be  dissolved  in  distilled 
water,  and  diluted  to  the  volume  of  1  litre,  the  solution  will  be 
of  the  required  strength,  i.  e.,  1  cubic  centimetre  will  exactly 
precipitate  0.010  gramme  of  chloride  of  sodium. 

Take  30  cubic  centimetres  of  the  filtrate  from  the  mixture  of 
baryta  mixture  and  urine,  and,  having  added  a  drop  of  nitric 
acid,  pour  in  from  a  burette,  or  from  a  finely  divided  pipette, 
twice,  as  many  cubic  centimetres  of  the  nitrate  of  silver  solu- 
tion as  the  number  of  cubic  centimetres  of  nitrate  of  mercury 
solution  required  in  the  chlorine  determination.  A  precipitate 
of  chloride  of  silver  will  fall,  and  the  filtrate  may  now  be  sub- 
jected to  analysis  for  urea. 

An  example  will  help  to  make  the  course  of  these  operations 
clear. 

Forty  cubic  centimetres  of  the  urine  of  a  boy  suffering  from 
typhus  fever  were  mixed  with  20  cubic  centimetres  of  baryta 
mixture,  and  the  fluid  was  filtered.  15  cubic  centimetres  of  the 
filtrate  was  placed  in  a  beaker,  and  the  standard  solution  of 
mercury  for  chlorine  was  added,  until  a  permanent  and  dense 
cloud  had  formed.  The  number  of  cubic  centimetres  added 
was  4.5.  As  each  cubic  centimetre  of  the  standard  solution 
corresponds  to  0.010  gramme  of  CI  calculated  as  NaCl,  the 
quantity  in  10  cubic  centimetres  amounted  to  0.045  gramme. 
30  cubic  centimetres  of  the  filtrate  from  the  baryta  mixture 
and  urine  were  now  taken  and  treated  with  4.5  X  2,  i.  e.,  9  cubic 
centimetres  of  nitrate  of  silver  solution.  The  fluid  was  filtered. 
Now  39  cubic  centimetres  of  the  mixture  of  urine,  baryta  so- 


550  THE    SECRETIONS. 

lution,  and  silver  nitrate  solution,  contained  20  cubic  centi- 
metres of  urine.  On,  therefore,  taking  :y  or  19.5  cubic  centi- 
metres of  the  filtrate,  after  the  precipitation  of  the  chloride  of 
silver,  we  obtained  a  quantity  of  fluid  which  contained  all  the 
urea  present  in  10  cubic  centimetres  of  the  original  urine. 

It  may  be  well  to  state  that  when,  as  in  many  cases  of  acute 
disease,  the  amount  of  chlorine  present  is  very  small,  nearly 
accurate  results  are  obtained,  if  no  correction  for  chlorine  be 
introduced. 

Other  corrections  must  be  introduced  into  Liebig's  method 
under  peculiar  circumstances :  these  will  be  stated  dogmati- 
cally, the  student  being  referred  to  larger  books  for  their  ex- 
planation. 

1st.  "When,  in  determining  the  amount  of  urea  in  15  cubic 
centimetres  of  mixture  of  urine  and  baryta  solution,  the  num- 
ber of  cubic  centimetres  of  mercury  solution  added  exceeds  30, 
we  must  repeat  the  operation,  adding  to  15  cubic  centimetres 
of  the  fluid  a  quantity  of  distilled  water  equal  to  the  difference 
between  30  and  the  number  required  in  the  first  operation. 

2d.  When  the  amount  of  solution  of  nitrate  of  mercury 
added  to  15  cubic  centimetres  of  the  filtrate  from  the  mixture 
of  urine  and  baryta  mixture,  is  less  than  30  cubic  centimetres, 
0.1  cubic  centimetre  must  be  subtracted  from  the  amount  of 
mercury  solution  required,  for  every  5  cubic  centimetres  less 
than  30  cubic  centimetres. 

This  correction  is  of  little  importance. 

II.  Davy's  method  for  the  determination  of  Urea. 

This  excellent  method  is  based  upon  the  fact  already  men- 
tioned, that  when  a  solution  of  urea  (CH4'Nv,0),  such  as  urine, 
is  treated  with  a  solution  of  hypochlorite,  it  splits  up  into  car- 
bonic acid,  water,  and  nitrogen  gas.  If  the  mixture  be  effected 
in  a  long  graduated  tube,  and  this  be  inverted  and  placed  over 
mercury,  the  whole  of  the  N  accumulates  on  the  surface  of  the 
fluid,  the  carbonic  acid  being  absorbed  by  the  solution  of  \\y- 
pochlorite  used.  From  the  volume  of  X  evolved  the  quantity 
of  urea  present  may  be  calculated.  (For  details  of  this  method 
the  reader  is  referred  to  a  Treatise  on  the  Pathology  of  the 
Urine,  by  Dr.  Thudichum,  London:  Churchill,  1858.) 

Davy's  process  is,  like  Liebig's,  not  absolutely  correct.  Uric 
acid,  and  other  nitrogenous  substances  present  in  urine,  are  de- 
composed by  hypochlorites  ;  as  their  quantity  is,  however,  com- 
paratively very  small,  the  error  introduced  is  not  large.  The 
writer  can  vouch,  from  personal  observations,  of  the  great  accu- 
racy of  this  method  when  applied  to  solutions  of  pure  urea,  and 
believes  that,  if  carried  out  with  the  apparatus  devised  by  Dr. 
Hiifner  for  the  determination  of  urea  by  solutions  of  alkaline 
hypobromites,  it  would  prove  the  most  useful  and  reliable 
method  for  the  determination  of  urea. 


BY    DR.    LAUDER    BRUNTON.  551 

*  196.  Determination  of  the  Amount  of  Uric  Acid 
in  Urine. — Uric  acid  is  usually  determined  by  precipitation 
with  dilute  nitric  or  hydrochloric  acid,  the  crystalline  precipi- 
tate being  washed,  dried,  and  weighed. 

Take  200  c.  c.  of  the  urine  and  add  to  it  5  c.  c.  of  dilute  hy- 
drochloric acid  of  density  1.11.  Set  aside  in  a  cellar  for  24 
hours.  Collect  the  uric  acid  on  a  weighed  filter,  and  wash 
thoroughly  with  distilled  water.  Dry  the  filter  and  uric  acid 
in  a  water  oven  at  a  temperature  of  100°  C.  Allow  the  dried 
filter  to  cool  under  an  exsiccator  (in  watch  glasses,  etc.)  and 
weigh.  The  weight  of  the  filter  and  uric  acid,  minus  the  weight 
of  the  filter  paper,  gives  the  amount  of  uric  acid  precipitated. 
To  this  must,  however,  be  added  the  quantity  of  uric  acid 
which  has  been  held  in  solution  by  the  urine  and  hydrochloric 
acid,  and  by  the  washings  of  the  filter.  The  whole  of  these 
fluids  are  therefore  mixed  and  measured,  and  for  every  100  c.  c. 
0.0038  grammes  of  uric  acid  must  be  calculated  (Neubauer). 
The  number  thus  calculated,  added  to  that  of  the  uric  acid  col- 
lected on  a  filter,  gives  the  amount  of  uric  acid  contained  in 
the  urine.  The  number  is,  however,  only  an  approximation  to 
the  truth.1 

**197.  Determination  of  the  Amount  of  Phosphoric 
Acid  contained  in  Urine. — The  phosphoric  acid  contained 
in  urine  exists  partly  in  a  state  of  combination  with  the  alka- 
line earths,  magnesia,  and  lime,  but  chiefly  in  combination  with 
alkalies.  If  we  render  the  urine  alkaline  by  the  addition  of  am- 
monia, the  former  are  precipitated,  leaving  the  alkaline  phos- 
phates in  solution.  It  is  customary  to  state  the  amount  of 
phosphoric  anhydride  corresponding  to  phosphoric  acid  in  the 
urine.  In  determining  the  quantity  of  phosphoric  acid  in  urine, 
we  may  merely  determine  the  total  quantity  existing  in  the 
fluid,  or  we  may  determine  the  total  quantity  first,  and  then 
the  quantity  which  remains  after  the  precipitation  of  the  earthy 
phosphates. 

The  volumetric  method  for  the  determination  of  phosphoric 
acid  in  urine  is  based  upon  the  following  reactions: — 

(a)  When  a  solution  of  a  phosphate  acidulated  with  acetic 
acid  is  treated  with  a  solution  of  nitrate  or  acetate  of  uranium, 
a  precipitate  falls  which  is  composed  of  uranium  phosphate. 

(6)  When  a  soluble  salt  of  uranium  is  added  to  a  solution  of 
potassium  ferrocyanide,  a  reddish-brown  precipitate  or  color  is 
developed. 

Preparation  of  Standard  Solutions  of  Uranium,  etc. — Before 
preparing  this  solution,  it  is  advisable  to  make  a  standard  solu- 

1  The  reader  is  referred  to  the  recent  researches  of  Dr.  Salkowsky,  in 
Virchow's  Archiv.  Bd.  52,  and  of  Maly,  Pfluger's  Archiv.  1872,  vol.  vi. 
p.  201. 


552  THE   SECRETIONS. 

tion  of  a  phosphate.  For  this  purpose,  10.085  grammes  of  well 
crystallized  sodium  phosphate  (XaHI'O, 4- 1211,0)  are  dis- 
solved in  distilled  water,  and  the  solution  diluted  to  one  litre. 
Fifty  cubic  centimetres  contain  0.1  gramme  of  P,Os. 

Then  100  grammes  of  sodium  acetate  are  dissolved  in  900  c.c, 
of  distilled  water,  and  100  c.c,  of  acetic  acid  added. 

The  solution  of  uranium  acetate  is  made  b}T  dissolving  com- 
mercial uranic  oxide  in  acetic  acid,  diluting  and  filtering;  or, 
instead,  a  solution  of  uranium  nitrate  may  be  made  hy  dissolv- 
ing the  crystallized  salt  in  water,  and  diluting.  The  solutions 
are  intended  to  contain  20.3  grammes  of  uranic  oxide  in  one 
litre  of  solution. 

Having  obtained  the  solution  of  uranium  acetate  or  nitrate, 
its  strength  is  determined  in  the  following  manner:  50  c.c.  of 
the  standard  solution  of  sodium  phosphate  are  placed  in  a 
beaker,  and  5  c.  c,  of  the  acid  solution  of  sodium  acetate  added. 
The  uranium  solution  is  poured  from  an  accuratel}7  graduated 
burette,  until  precipitation  ceases.  Then  a  few  drops  of  a 
solution  of  potassium  ferrocyanide  are  placed  on  a  porcelain 
slab,  and  after  each  addition  of  uranium  solution  to  the  phos- 
phate, a  drop  of  the  mixture  is  taken  up  by  means  of  a  glass 
rod  and  brought  in  contact  with  the  ferrocyanide.  As  soon  as 
an  excess  of  uranium  solution  has  been  added,  the  character- 
istic reddish-brown  color  of  uranium  ferrocyanide  is  observed. 

It  is  convenient  to  graduate  the  solution  of  uranium  so  that 
20  cubic  centimetres  shall  be  exactly  equal  to  50  c.  c.  of  the 
standard  solution  of  phosphate  of  soda,  i.e.,  to  0.1  gramme  of 

PA- 

In  analyzing  urine  by  means  of  solutions  of  uranium,  it  is 
convenient  to  operate  on  50  c.  c.  This  quantity  of  urine  is 
treated  with  the  acetate  of  sodium  solution  and  heated  on  the 
water-bath  to  a  temperature  approaching  100°  C. ;  it  is  then 
treated  with  the  solution  of  uranium  as  previously  described. 

198.  Determination  of  the  Quantity  of  Sulphuric 
Acid  in  Urine. — The  quantity  of  sulphuric  acid  in  urine  is 
best  determined  by  precipitating  with  chloride  of  barium  and 
weighing  the  dried  and  burned  precipitate  of  barium  sulphate  ; 
from  this  the  amount  of  sulphuric  acid  can  be  calculated.  It 
is  usual  to  state  the  amount  of  sulphuric  anhydride  (S03)  cor- 
responding to  the  sulphuric  acid  existing  in  the  urine. 

For  details  as  to  the  precaution  to  be  used  in  determining 
the  amount  of  sulphuric  acid  by  precipitation,  the  student  is 
referred  to  Fresenius's  Quantitative  Analysis.  The  manipula- 
tions involved  in  such  an  analysis,  however  simple  it  may  be, 
can  only  be  learned  in  a  laboratoiy  devoted  to  pure  chemistry. 

It  has  been  suggested  that  the  sulphuric  acid  in  urine  should 
be  determined  by  means  of  a  standard  solution  of  chloride  of 
barium  ;  the  method  is  one,  however,  which  is  tedious,  and 


BY    DR.    LAUDER    BRUNTON.  553 

which  cannot  be  recommended,  even  on  the  score  of  rapidity, 
as  preferable  to  the  one  first  described. 

**  199.  Detection  of  Su^ar  in  Urine.— It  is  still  a  mat- 
ter of  doubt  whether  the  urine  in  health  contains  sugar;  the 
processes  which  have  been  suggested,  for  the  separation  of  this 
substance,  by  those  who  maintain  its  constant  occurrence  in 
healthy  urine,  are,  however,  complicated  ;  and,  as  they  have  led 
to  veiy  various  results  in  the  hands  of  different  observers, 
their  consideration  would  be  out  of  place  in  this  book.  (See 
Pfliiger's  Archiv.  fur  Physiol.  V.  pp.  359  and  375.) 

When  present  in  abnormal  quantities  in  urine,  as  in  diabetes, 
glucose  ma}'  be  very  readily  detected.  The  following  experi- 
ments will  be  sufficient  to  make  the  student  acquainted  with 
the  more  common  reactions. 

Experiment  1.  Take  5  cubic  centimetres  of  diabetic  urine,  or 
of  a  solution  of  grape-sugar,  and  add  to  it  two  or  three  drops 
of  a  solution  of  copper  sulphate,  so  that  a  very  slight  green 
tinge  is  perceptible  ;  then  add  to  the  fluid  a  solution  of  caustic 
soda,  or  potash,  until  the  precipitate  of  hydrate  copper  oxide, 
at  first  formed,  is  redissolved. 

The  fluid,  which  has  assumed  a  blue  tint,  is  now  boiled,  when 
an  abundant  precipitate  of  cuprous  oxide  falls  ;  before  this  has 
separated,  the  fluid  in  which  the  precipitation  is  effected  be- 
comes opaque,  and  presents  a  reddish-yellow  color.  This  is 
known  as  Trommer's  test  (.see  §  "IT  and  §  12). 

2.  To  five  cubic  centimetres  of  urine  add  nearly  an  equal 
volume  of  a  solution  of  caustic  soda,  or  potash,  and  boil.  The 
fluid  will  assume  at  first  a  light-yellow,  then  an  amber,  and 
lastly  a  dark-brown  coloration.    Tins  is  known  as  More's  test. 

3.  Some  diabetic  urine  is  mixed  with  a  little  brewer's  yeast, 
and  the  mixture  is  poured  into  a  test-tube  half  full  of  mercury  ; 
the  orifice  of  the  tube  is  closed  with  the  thumb,  and  the  tube 
is  inverted  into  a  capsule  containing  mercury. 

After  a  period  of  twent}T-four  hours,  at  ordinary  tempera- 
tures, the  test-tube  will  be  found  to  contain  large  quantities  of 
carbonic  acid  gas,  which  can  be  readily  absorbed  by  passing 
up  into  the  tube  a  fragment  of  caustic  potash. 

In  addition  to  these  tests,  the  student  may  with  advantage 
determine,  by  means  of  a  polariscope,  that  diabetic  urine  pos- 
sesses the  property  of  rotating  the  plane  of  polarized  light  to 
the  right. 

**  200.  Determination  of  the  Quantity  of  Sugar  in 
Urine. — Tins  may  be  best  effected  b}r  one  of  the  two  follow- 
ing methods  :  firstly,  by  determining  to  what  extent  a  known 
depth  of  the  saccharine  fluid  rotates  the  plane  of  polarized 
light  to  the  right;  or,  secondly,  by  determining  the  quantity 
of  urine  which  has  to  be  boiled  with  a  standard  solution  of 


554  THE    SECRETIONS. 

a  cupric  salt,  in  order  to  reduce  the  whole  of  the  copper  to 
the  condition  of  red  cuprous  oxide. 

In  order  to  determine  the  quantity  of  sugar  by  the  last 
method,  which  is  known  as  that  of  Fehling,  we  require  to 
prepare  a  standard  solution  in  the  following  manner :  34.65 
grammes  of  pure  and  well  crystallized  copper  sulphate  are 
dissolved  in  about  1G0  cubic  centimetres  of  water,  and  173 
grammes  of  Rochelle  salts  (tartrate  of  potash  and  soda)  are 
dissolved  in  about  (iOO  cubic  centimetres  of  solution  of  caustic 
soda,  having  a  specific  gravity  of  1120.  The  solution  of  sul- 
phate of  copper  is  added  gradually  to  the  alkaline  solution  of 
Rochelle  salts,  the  fluid  being  continually  stirred.  A  deep 
blue  solution  is  thus  obtained,  which  is  diluted  with  distilled 
water  to  the  volume  of  one  litre.  Ten  cubic  centimetres  of 
this  solution  are  reduced  by  0.05  gramme  of  diabetic  sugar. 

The  following  is  the  process  which  has  to  be  followed  in 
determining  the  quantity  of  sugar  in  urine: — 

The  urine  to  be  examined  is  diluted  to  a  known  extent; 
thus  in  the  case  of  a  diabetic  urine,  having  a  specific  gravity 
of  1040,  100  cubic  centimetres  are  diluted  with  distilled  water 
to  the  volume  of  1000  cubic  centimetres. 

Ten  cubic  centimetres  of  the  standard  copper  solution  are 
then  accurate^  measured  out  and  poured  into  a  porcelain 
capsule.  Forty  cubic  centimetres  of  distilled  water  are  added, 
and  the  solution  in  the  capsule  boiled. 

The  previously  diluted  urine  is  then  allowed  to  flow  in  from 
a  burette ;  after  a  few  cubic  centimetres  have  been  added,  the 
fluid  in  the  capsule  is  briskly  boiled,  and  then  the  application 
of  heat  discontinued  for  a  few  seconds. 

The  solution,  which,  after  the  saccharine  fluid  has  been 
boiled  with  it,  assumes  a  red  color,  deposits  a  red  sediment  of 
cuprous  oxide,  whilst  the  supernatant  fluid  retains  a  more  or 
less  blue  color,  in  consequence  of  a  portion  of  the  copper 
remaining  in  solution. 

Successive  portions  of  the  diluted  urine  are  then  added,  and 
the  fluid  boiled  after  each  addition.  As  the  operation  proceeds, 
the  addition  of  the  diluted  urine  is  performed  with  great  care, 
only  a  few  drops  being  poured  in  at  a  time.  A  point  is  at  last 
reached  when  the  bottom  of  the  capsule  is  coated  with  a  de- 
posit of  red  cuprous  oxide,  and  when,  on  tilting  the  capsule 
so  as  to  bring  the  fluid,  which  it  contains,  over  the  clean  white 
sides,  no  tint  of  blue  is  perceived. 

The  number  of  cubic  centimetres  of  sugar  solution  added  is 
then  read  off  and  marked.  It  is  advisable,  however,  to  pur- 
sue the  operation  one  step  further.  A  few  more  drops  of 
diluted  urine  are  added  to  the  contents  of  the  basin,  which 
are  again  boiled,  and  if  necessary,  the  addition  is  repeated 
until  the  boiled  fluid  becomes  faintly  opaque  and  of  a  yellowish 


BY    DR.    LAUDER   BRUNTON.  555 

color.  These  appearances  prove  that  a  slight  excess  of  sugar 
solution  has  been  added.  The  number  of  cubic  centimetres  of 
diluted  urine  added  is  again  read  off.  If  the  arithmetic  mean 
of  the  first  and  second  results  be  now  taken,  a  number  will  be 
obtained  which  represents,  very  accurately,  the  volume  of  the 
dilute  urine,  in  cubic  centimetres,  which  was  capable  of  re- 
ducing the  whole  of  the  copper  in  ten  cubic  centimetres  of 
the  standard  solution  employed.  Now,  as  this  volume  of 
copper  solution  is  reducible  by  exactly  0.05  gramme  of  dia- 
betic sugar,  this  quantity  must  have  been  present  in  the 
volume  of  diluted  urine  made  use  of.  An  example  will  render 
the  calculations  required  intelligible :  The  urine  of  a  diabetic 
patient  was  found  to  have  a  specific  gravity  of  1035.  100 
cubic  centimetres  were  placed  in  a  litre  flask,  and  distilled 
water  added  until  the  fluid  exactly  measured  1000  c.  c.  Ten 
cubic  centimetres  of  standard  copper  solution  required  30.49 
c.  c.  of  the  diluted  urine  in  order  to  be  completely  reduced,  or 
30.49  c.  c.  of  the  diluted  urine  contained  0.05  gramme  of  sugar. 
As  the  urine  had  been  diluted  to  ten  times  its  original  bulk, 
the  same  volume  of  the  undiluted  urine  would  contain  ten 
times  as  much  sugar,  i.  e.,  0.5  gramme  of  sugar.  From  these 
data  we  can  easily  ascertain  how  much  sugar  was  passed  in 
the  twentj'-four  hours. 

Thus,  if  the  quantity  of  urine  passed  in  twent3'-four  hours, 
in  the  case  under  consideration,  amounted  to  3000  cubic 
centimetres,  the  amount  of  sugar  passed  during  the  same 
period  would  be  at  once  found  by  the  following  proportion : — 

30.49  :  0.5  :  :  3000  :  x 

=  49.19  grammes. 

The  student,  in  carrying  out  the  process  just  described,  must 
be  careful  to  dilute  the  urine  to  a  sufficient  extent.  In  cases 
where  the  percentage  of  sugar  is  very  large,  it  is,  for  instance, 
convenient  to  dilute  the  urine  twenty  times  instead  of  ten. 

**  201.  Detection  of  Albumin  in  Urine. — Except  in 
very  exceptional  cases,  which  need  not  be  alluded  to  here,  the 
only  albuminous  body  proper  which  appears  in  urine  possesses 
the  reaction  of  serum  albumin.  Accordingly,  when  albumi- 
nous urine  is  boiled,  it  is  found  to  be  coagulable,  i.  e.,  the 
albumin  separates  in  the  insoluble  form,  and  the  coagulated 
albumin  is  insoluble  in  nitric  acid.  Nitric  acid,  when  added 
alone  to  urine  containing  albumin,  likewise  precipitates  that 
substance,  and  the  precipitate  is  not  dispelled  by  heat.  It 
must  be  stated,  however,  that  in  certain  cases,  when  nitric  acid 
produces  a  mere  haze,  this  may  disappear  on  boiling,  although 
it  be  really  due  to  a  trace  of  albumin.  Albuminous  urine 
possesses  the  property  of  rotating  the  plane  of  polarization  to 
the  left. 


556  Till:   SECRETIONS. 

*  202.  Determination  of  the  Amount  of  Albumin  in 
Urine. — A  known  volume  of  the  urine,  say  50  or  100  cubic 
centimetres,  is  boiled  ;  if  the  reaction  is  alkaline  or  neutral,  a 
trace  of  acetic  acid  being  previously  added,  the  albumin  sepa- 
rates freely  and  is  collected  on  a  weighed  filter.  The  substance 
on  the  filter  is  repeatedly  washed  with  boiling  water,  and 
after  being  allowed  to  drain,  it  is  dried,  first  in  a  water  oven  at 
100°  C,  and  afterwards  in  an  air  oven  at  120°  C.  The  weight 
of  the  filter  and  albumin,  minus  the  weight  of  the  filter,  fur- 
nishes us  with  the  quantity  of  albumin  (with  adhering  salts) 
present  in  the  quantity  of  urine  taken  for  analysis. 

When  a  large  number  of  determinations  of  albumin  in  urine 
have  to  be  made,  it  is  advisable  to  make  use  of  the  polariscope. 
The  extent  to  which  the  plane  of  polarized  light  is  rotated  to 
the  left  bears  a  strict  relation  to  the  quantity  of  albumin  present 
in  a  fluid,  providing  the  depth  of  fluid  examined  be  the  same, 
and  that  no  other  substance  (e.  g.,  sugar)  be  present,  exerting 
an  opposite  action  on  polarized  light. 

**  203.  Detection  of  Bile-coloring  Matter  in  Urine. 
— When  a  large  quantity  of  bilirubin  is  present  in  urine  it  may 
be  separated  from  it  by  agitating  the  fluid  with  chloroform, 
decanting,  evaporating  the  chloroform  solution,  dissolving  the 
residue  in  pure  chloroform,  and  allowing  the  fluid  to  evaporate 
spontaneously.  In  this  way  red  rhombic  prisms  of  bilirubin 
may  be  obtained. 

In  all  cases  where  bile-coloring  matter  is  present,  we  can  de- 
tect it  by  the  well  known  reaction  with  nitric  acid  (Gmelin's 
reaction).  If  strong  nitric  acid,  containing  nitrous  acid,  be 
added  to  a  thin  stratum  of  urine  containing  bile,  in  a  flat  por- 
celain dish,  a  succession  of  beautiful  tints  is  perceived.  The 
fluid  is  seen  at  first  to  be  green,  then  blue  and  violet ;  it  then 
assumes  a  rather  dirty  claret,  and  ultimately  a  dirty  yellow 
color  (.see  §  135). 

In  cases  where  a  very  satisfactory  search  for  traces  of  bili- 
rubin is  to  be  made,  it  is  advisable  to  separate  it  from  the  urine, 
by  means  of  chloroform,  and  then  to  test  the  evaporated  residue 
with  nitric  acid.  A  property  which  is  very  characteristic  of 
urine  or  other  animal  fluids  colored  by  bile  pigment,  is  that  of 
staining,  of  a  yellow  color,  linen  which  is  moistened  with  it. 

**  204.  Separation  and  Detection  of  Bile  Acids  in 
Urine. — Four  or  five  hundred  cubic  centimetres  of  urine 
are  treated  with  acetate  of  lead  until  a  precipitate  ceases  to  fall, 
and  then  solution  of  ammonia  is  added.  The  precipitate  is 
collected  on  a  filter,  washed  with  water,  and  allowed  to  drain. 
The  filter  paper,  with  the  very  bulky  precipitate  which  it  con- 
tains, is  then  boiled  in  a  flask,  with  alcohol,  and  the  solution  is 
filtered  whilst  hot.  A  few  drops  of  solution  of  sodium  carbo- 
nate being  added,  the  fluid  is  evaporated  to  dryness  on  the 


BY    DR.    LAUDER    BRUNTON.  557 

water-bath.  The  residue  is  boiled  with  absolute  alcohol,  and 
the  solution  is  concentrated  to  a  small  volume.  On  adding  an 
excess  of  ether  to  the  alcohol,  a  precipitate  occurs  which  con- 
sists of  the  soda  salts  of  the  bile  acids,  and  which,  if  set  aside 
for  some  time,  often  crystallizes. 

This  precipitate  may  be  obtained  by  decanting  from  it  the 
supernatant  mixture  of  alcohol  and  ether.  It  is  soluble  in 
water  ;  a  few  drops  of  the  aqueous  solution  ma}'  be  evaporated 
to  dryness  in  a  porcelain  capsule  and  then  subjected  to  Petten- 
kofer's  test.  This  consists  in  adding  a  few  drops  of  pure  sul- 
phuric acid,  and  then  a  trace  of  solution  of  cane  sugar  to  it, 
and  heating  very  gently.  After  some  time,  an  exceedingly 
beautiful  purple-violet  coloration  is  developed. 

Bile  acids  may  be  detected  in  the  urine  without  previous 
separation  b}-  employing  Strasburg's  method  (see  §140),  but 
Hoppe-Seyler's  method  just  described  is  much  more  reliable. 

205.  Detection  of  Blood  in  Urine. — Urine  which  con- 
tains blood,  on  being  allowed  to  stand,  usually  furnishes  a  de- 
posit in  which  characteristic  blood  corpuscles  may  be  discovered 
without  difficult}'. 

On  examiningsuch  urine  by  means  of  the  spectroscope,  there 
is  usualty  no  difficulty  in  observing  the  spectrum  of  haemoglo- 
bin or  of  hsematin. 

Urine  which  contains  haemoglobin  furnishes,  when  boiled,  a 
precipitate  of  albumin  and  haematin.1 

1  Although  it  has  been  considered  adivisable  to  devote  some  space  to 
the  mode  of  detecting  a  few  of  the  more  important  abnormal  constituents 
of  urine,  it  would  be  beyond  the  object  of  this  book  to  give  a  complete 
account  of  the  properties  of,  and  mode  of  separating,  all  the  substances 
which  occur  in  urine  in  a  state  of  disease.  Any  additional  information 
on  these  subjects  is  to  be  found  in  the  very  valuable  "  Handbuch  der 
physiologisch-  und  pathologisch-Chemischen  Analjrsen  of  Professor 
Hoppe-Seyler,  to  which  reference  has  been  already  made. 


APPENDIX. 


CHAPTER   XXXIX. 

PRACTICAL  NOTES  ON  MANIPULATION. 

208.  Manipulation  of  Glass  Tubing. — Most  laboratories  contain 
a  glass-blower's  table  ;  in  its  absence  the  mouth  gas  blowpipe  must  be 
used.  The  difficulty  of  keeping  up  a  continuous  blast  of  air  with  this 
instrument  can  be  readily  overcome  by  practice,  provided  that  the  orifice 
is  not  too  wide.  The  blowpipe  flame  (fig.  325)  consists  of  two  parts,  an 
inner  blue  cone  («)  which  is  the  deoxidizing  or  reducing  flame,  and  an 
outer  envelope  (5)  which  surrounds  it.  The  hottest  part  of  the  flame 
is  a  very  little  in  front  of  the  tip  of  the  blue  cone.  The  reducing  flame 
is  so  called  because  the  unburnt  gasses  present  in  it  have  at  that  high 
temperature  a  great  tendency  to  take  oxygen  from  any  substance  con- 
taining it.  In  the  outer  envelope,  on  the  contrary,  the  supply  of  oxy- 
gen is  abundant ;  it  is  therefore  called  the  oxidizing  flame.  Ordinary 
English  glass  tubing  contains  oxide  of  lead  :  when  it  is  heated  in  the 
reducing  flame,  black  stains  of  metallic  lead  form  on  its  surface.  To 
avoid  this,  it  should  always  be  heated  in  the  extremity  of  the  outer  flame. 
German  glass  is  free  from  lead,  and  much  less  fusible  than  English  glass, 
and  is  generally  preferable  to  it.  Tubes  of  German  glass  may  be  dis- 
tinguished from  English  by  looking  through  them  lengthwise  ;  the  for- 
mer has  a  greenish  color,  while  the  latter  looks  dark.  In  drawing  out 
a  glass  tube  so  as  to  form  a  pipette  (see  fig.  326),  care  must  be  taken  to 
soften  the  part  to  be  drawn  completely  and  equally,  and  to  remove  it 
from  the  flame  before  extending  it.  If  this  precaution  is  neglected,  the 
drawn-out  part  will  collapse  and  close.  When  heating  a  tube  for  the 
purpose  of  bending,  it  is  important  to  use  as  low  a  temperature  as  is 
sufficient  to  soften  it,  and  not  to  begin  to  bend  until  a  considerable  ex- 
tent of  the  part  to  be  bent  is  equally  softened.  For  this  reason,  it  is  best 
to  use  a  large  flame  (that  from  a  gas  jet  being  preferable  to  a  Bunsen's 
lamp  or  blowpipe),  in  which  the  tube  must  be  moved  up  and  down 
until  the  object  is  attained.  Before  bending,  it  must  of  course  be  re- 
moved from  the  flame.  In  bending  a  thin  tube,  especially,  if  it  be 
heated  too  strongly,  it  is  difficult  to  avoid  its  becoming  wrinkled  at  the 
bend.  To  avoid  this,  it  is  a  good  plan  to  close  one  end  air-tight 
and  blow  in  gently  at  the  other  during  flexion.  Large  tubes  are  bent 
more  easily  by  filling  them  with  clean  dry  sand  and  heating  them  over 
incandescent  charcoal,  supported  on  wire  netting.  To  seal  a  tube,  it 
must  be  thoroughly  softened  at  a  short  distance  from  its  end,  and  drawn 
out  quickly  to  a  thread.  The  capillary  part  of  a  tube  already  drawn  out 
is  sealed  instantaneously  by  directing  the  point  of  a  small  blowpipe 
flame  upon  it  and  extending  the  heated  part  (fig.  327).  To  close  a  tube 
at  its  end,  another  piece  of  the  same  kind  of  glass  must  be  joined  to  it 


5G0  APPENDIX. 

by  fusing  the  ends  of  both  in  the  same  flame.  As  soon  as  the  joining 
has  cooled  slightly,  the  tube  to  be  closed  is  heated  again  at  a  short  dis- 
tance from  its  end,  and  drawn  out  as  before 

Annealing. — After  glass  has  been  strongly  heated  it  must  be  allowed 
to  cool  as  gradually  as  possible,  in  order  to  anneal  it. 

Manipulation  of  Corks. — To  fit  properly,  a  cork  must  be  somewhat 
larger  than  the  opening  it  is  intended  to  fill.  Before  pushing  it  in,  it 
should  always  be  reduced  by  compression,  either  with  a  cork  squeeze! 
or,  in  its  absence,  by  rolling  it  on  the  floor  (protected  by  a  covering  of 
paper)  under  the  foot.  For  shaping  corks,  a  shoemaker's  knife  which 
has  been  sharpened  on  a  rough  stone  answers  best.  Any  knife  with  a 
keen  edge  will  do.  To  perforate  a  cork,  a  piece  of  brass  tubing,  the 
edge  of  one  end  of  which  is  sharpened,  is  used.  It  is  best  to  work  the 
borer  from  the  opposite  ends,  the  two  bore-holes  meeting  in  the  middle. 
As  the  holes  always  require  finishing  with  a  rat's  tail  file,  a  borer 
smaller  than  the  intended  channel  should  be  used. 

207.  Solution  and  Ebullition. — The  different  solubility  of  various 
organic  substances  in  reagents,  such  as  water,  ether,  alcohol,  acids, 
alkalies,  and  saline  solutions,  not  only  serves  as  a  means  of  separating 
them  from  each  other,  but  in  many  instances,  as  in  the  case  of  albumi- 
nous bodies,  furnishes  a  characteristic  by  which  one  substance  may  be 
distinguished  from  others  nearly  allied  to  it.  Tests  are  also  more  gene- 
rally and  conveniently  applied  to  solutions  than  to  bodies  themselves. 
Solution  takes  place  more  readily  when  the  body  to  be  dissolved  is  finely 
divided.  Dry  and  hard  substances  are  therefore  generally  pulverized  by 
pounding  and  rubbing  in  a  Wedgewood  mortar.  If  too  large  to  be  con- 
veniently triturated  at  once,  they  may  be  previously  broken  in  an  iron 
mortar,  or  by  wrapping  them  loosely  in  brown  paper  and  pounding 
them  with  a  hammer.  If  the  substance  is  constantly  shaken  or  stirred 
about  so  as  to  bring  it  continually  into  contact  with  fresh  portions  of  the 
solvent,  it  will  dissolve  much  more  quickly  than  if  allowed  to  remain 
at  rest. 

For  preparing  Solutions. — A  beaker  is  for  most  purposes  the  most 
convenient  vessel,  as  its  contents  can  be  stirred  at  the  same  time  that  it 
is  subjected  to  heat,  which  always  accelerates  solution.  To  avoid  risk 
of  fracture,  the  beaker  must  not  be  heated  over  a  naked  flame,  but  must 
be  placed  on  a  piece  of  wire  gauze  or  sand  bath  (fig.  328),  supported  on 
a  tripod.  Flasks  may  be  employed  instead  of  beakers  for  solution  or 
boiling  when  stirring  is  not  required.  They  have  the  advantage  of 
preventing  loss  of  fluid  during  the  process  of  ebullition,  as  any  particles 
which  spurt  up  are  caught  against  the  sides  of  the  flask,  especially  if 
it  is  placed  in  an  inclined  position,  instead  of  falling  outside  as  in  a 
beaker. 

To  prevent  Loss  by  Evaporation. — Various  methods  may  be  used.  One 
of  these  consists  in  placing  a  small  funnel  in  the  mouth  of  the  flask  ; 
the  fluid  condenses  in  the  funnel  and  runs  back  into  the  fiask.  Another 
method  is  to  close  the  neck  of  the  flask  with  a  cork,  through  which  a 
wide  glass  tube,  drawn  out  to  a  capillary  opening  at  its  upper  end,  is 
passed.  A  considerable  part  of  the  vapor  passing  from  the  boiling  liquid 
is  condensed  in  the  tube  and  falls  back  into  the  flask.  If  the  boiling 
is  long  continued,  the  tube  gets  very  hot  and  a  great  deal  of  vapor 
escapes.  To  avoid  this,  the  escape  tube  is  prolonged  and  surrounded 
by  a  Liebig's  condenser,  for  which  purpose  it  must  be  bent  at  an  angle 
of  about  120u,  as  seen  in  fig.  329. 

To  exhaust  a  substance  with  ether,  the  ether  and  the  substance  should 
be  placed  in  one  flask,  with  which  a  second  is  connected  by  a  bent  glass 
tube  which  passes  through  the  cork  of  both.  The  tube,  which  scarcely 
projects  beyond  the  under  surface  of  the  cork  in  the  first  flask,  reaches 


BY   DR.    LAUDER   BRUNTON.  561 

to  the  bottom  of  the  second.  The  first  flask  being  then  placed  in  a 
beaker  of  warm  water  and  the  second  in  cold,  the  ether  distils  over 
from  the  former  into  the  latter  and  is  condensed.  When  a  large  quan- 
tity of  the  ether  has  passed  over,  the  flasks  are  transposed,  when  the 
whole  of  the  ether  rushes  back  into  the  first  flask.  The  process  may  be 
repeated  indefinitely. 

In  connection  with  this  subject,  an  arrangement  may  be  described 
which  is  chiefly  used  for  washing  precipitates.  It  is  also  applicable  for 
the  purpose  of  replacing  loss  by  evaporation  when  liquids  are  boiled,  or 
to  keep  the  water  at  a  constant  level  in  a  water-bath.  (See  fig.  331.) 
It  consists  of  a  large  flask,  a,  fitted  with  a  cork,  through  which  pass 
two  tubes.  One  of  these,  b,  c,  is  straight  and  open  at  both  ends  ;  the 
other,  d,  e,  g,  f,  is  bent  so  as  to  form  a  syphon,  the  limbs  of  which  are 
of  equal  length.  Both  ends  of  d,  e,  g,  /,  are  at  a  somewhat  lower  level 
than  the  lower  end  of  b,  c.  The  end  is  placed  in  the  funnel  or  water- 
bath  at  such  a  height  that  the  level  of  the  lower  end  of  b,  c,  coincides 
with  that  at  which  it  is  desired  that  the  surface  of  the  fluid  shall  remain. 
The  effective  difference  in  the  limbs  of  the  syphon  is  the  space  between 
c  and  d.  Whenever  the  surface  of  the  liquid  in  the  funnel  or  bath  is  on 
a  level  with  c,  the  tube  d,  e,  g,  /,  ceases  to  act  as  a  syphon  ;  but  as  soon 
as  it  falls,  d,  f,  again  acts,  and  liquid  runs  into  the  funnel  till  the  surface 
is  again  level  with  c. 

208.  Evaporation. — Evaporation  of  watery  liquids  is  usually  con- 
ducted in  shallow  basins  of  Berlin  porcelain,  heated  either  directly  in  a 
sand-bath  or  over  a  water-bath.  An  ordinary  saucepan  answers  per- 
fectly as  a  water-bath.  (See  fig.  330.)  If  the  naked  flame  is  used,  it 
ought  not  to  be  allowed  actually  to  touch  the  bottom  of  the  basin.  The 
process  is  greatly  accelerated  by  constant  stirring. 

If  it  is  important  that  none  of  the  substance  be  lost,  the  liquid  must 
not  be  heated  to  boiling,  as  it  is  then  apt  to  spirt  over  the  sides.  In 
evaporating  a  solution  to  dryness,  its  surface  often  becomes  covered 
towards  the  end  of  the  process  with  a  pellicle,  which  hinders  the  vapor 
below  from  escaping  easily,  and  thus  both  retards  evaporation  and 
causes  the  vapor  to  issue  in  jets  which  may  occasion  loss  of  material. 
The  formation  of  the  pellicle  is  best  prevented  by  stirring  the  fluid  con- 
stantly with  a  glass  rod.  It  may  also  be  prevented  by  covering  the 
evaporating  basin  loosely  with  another  somewhat  smaller  one,  or  with 
a  concave  glass  with  the  concavity  downwards,  but  this  retards  evapo- 
ration. Solutions  in  alcohol,  ether,  and  chloroform  must  be  evaporated 
in  beakers.  Solutions  in  the  two  latter  menstrua  must  never  be  evapo- 
rated over  a  naked  flame,  but  always  on  a  water-bath,  as  their  vapor  is 
inflammable. 

Krciporation  at  a  Constant  Medium  Temperature. — It  is  sometimes 
desirable  to  evaporate  a  liquid  at  a  constant  medium  temperature,  such 
as  40°  C.  This  may  be  done  roughly  by  placing  the  evaporating  basin 
in  a  sand-bath,  and  carefully  regulating  the  size  of  the  flame  by  a 
thermometer.  Unless,  however,  it  is  constantly  watched,  the  tempera- 
ture is  apt  to  rise  or  fall  too  much,  and  the  solution  may  get  spoiled. 
This  difficulty  is  avoided  by  using  a  water-hath  heated  by  a  gas-lamp, 
which  is  connected  with  a  Bunsen's  gas-regulator.  For  this  purpose  I 
find  a  water-bath  of  the  accompanying  form  (fig.  331)  a  convenient 
one.  It  is  made  of  galvanized  zinc,  is  eleven  inches  in  diameter,  and 
five  deep.  At  one  side  it  bulges  out,  and  in  the  projecting  part  thus 
formed  the  thermometer  and  regulator  are  placed.  The  top  of  the  bath 
is  covered  by  a  zinc  plate  perforated  by  several  large  holes,  in  which 
evaporating  basins  may  be  put;  or  by  a  series  of  concentric  copper 
rings,  "no  or  more  of  which  maybe  removed  so  as  to  accommodate 
evaporating  basins  of  different  sizes.  The  regulator,  as  modified  by 
36 


562  APPENDIX. 

Gcissler  (fig.  332),  consists  of  a  wide  glade  tube,  a,  divided  into  two 
parts,  an  upper  and  a  lower,  by  a  horizontal  septula.  In  the  middle  of 
the  septum  is  an  opening,  from  which  a  tube  runs  down  nearly  to  the 

bottom  of  the  lower  division.  The  tube  is  closed  by  a  perforated  cork 
or  India-rubber  stopper.  Through  this  passes  a  tube,  is,  with  a  hori- 
zontal limb,  e.  Inside  B  is  a  smaller  and  shorter  tube,  C,  which  has  a 
very  small  opening  opposite  r>.  The  sides  of  n  and  <  are  luted  together 
with  cement  at  v.  In  using  this  regulator,  a  quantity  of  mercury  is 
poured  into  a,  and  of  course  runs  down  into  the  lower  division,  partly 
filling  it,  and  partly  compressing  the  air  it  contains. 

The  mouth  of  a  is  then  closed  by  the  cork,  and  the  tube  c  connected 
by  India-rubber  tubing  with  a  gas-pipe,  and  the  tube  e  with  a  small 
gas-burner.  The  gas  passes  down  the  tube  c  through  its  lower  open 
end,  up  again  between  it  and  B,  and  out  at  E,  and  thence  to  the  burner. 
The  regulator  and  a  thermometer  are  then  immersed  in  the  water-bath, 
the  gas  lighted,  and  the  bath  warmed  till  the  thermometer  indicates 
40°  C.,  or  any  other  desired  temperature.  The  tubes  B  and  c  are  then 
pushed  down  till  the  mercury  touches  the  lower  end  of  c  and  closes  it. 
The  gas  is  thus  prevented  from  passing  onwards  to  the  burner,  and  the 
flame  would  go  out  entirely  were  it  not  that  the  small  bole  in  c,  oppo- 
site D,  allows  sufficient  gas  to  pass  through  it  to  preserve  the  flame  from 
being  completely  extinguished.  As  soon  as  the  flame' is  thus  diminished, 
the  water-bath  and  the  regulator  immersed  in  it  begin  to  cool,  and  the 
mercury,  and  still  more  the  air  in  the  regulator,  conserpiently  contracts. 
The  mercury,  therefore,  sinks,  and  leaves  the  mouth  of  c  open,  so  that 
the  gas  again  passes  freely  through  it.  the  flame  increases,  and  the  tem- 
perature of  the  bath  again  rises.  The  mercury  and  air  again  expand  ; 
and  as  soon  as  the  temperature  is  reached  to  which  the  regulator  was 
adjusted,  the  mercury  again  closes  the  mouth  of  c,  and  cuts  off  the  gas 
till  the  temperature  again  falls.  In  this  way  the  temperature  may  be 
kept  for  months  at  40°  without  varying  much  more  than  half  a  degree. 
Unless  the  mercury  is  very  clean,  however,  it  will  adhere  slightly  to 
the  lower  end  of  c,  and  the  variations  will  thus  be  greater.  The  water 
in  the  bath  must  also  be  kept  at  a  constant  level,  as  otherwise  the  part 
of  the  regulator  heated  by  it  is  sometimes  greater  and  sometimes  less. 
The  mercury  consequently  does  not  always  expand  in  the  same  pro- 
portion to  the  rise  in  the  temperature  of  the  water  in  which  it  is  par- 
tially immersed,  and  variations  of  several  degrees  may  thus  be  produced. 

209.  Precipitation. — Iu  precipitating  a  substance  by  the  addition 
of  another,  the  reagent  is  generally  added  a  little  at  a  time,  and  mixed 
by  means  of  a  stirring  rod,  till  a  further  addition  of  the  reagent,  produces 
no  perceptible  increase  iu  the  amount  of  the  precipitate.  In  order  to 
ascertain  that  the  precipitation  is  complete,  a  little  of  the  liquid  is  tested 
by  throwing  it  on  a  filter,  and  the  reagent  added  to  the  clear  filtrate. 
If  no  further  precipitate  occurs,  the  precipitation  is  complete  ;  but  if 
one  is  formed,  the  filtrate  is  again  mixed  with  the  rest  of  the  fluid  and 
the  process  repeated. 

210.  Washing  of  Precipitates  on  Filters. — Precipitates  are  gene- 
rally collected  on  a  filter  and  washed  by  directing  a  stream  of  water  or 
alcohol  on  them  by  means  of  a  wash-bottle.  The  filter  should  never  be 
filled  up  to  the  top,  as  the  upper  part  of  the  precipitate  cannot  then  be 
properly  washed.  It  is  always  advisable  to  let  the  precipitate  settle  in 
the  beaker,  and  to  allow  the  clear  liquid  to  passs  through  the  filter 
before  throwing  the  precipitate  itself  upon  it  ;  and  the  whole  of  the 
fluid  from  which  the  precipitate  has  subsided  must  be  allowed  to  pass 
through  the  filter  before  the  washing  is  begun.  A  stream  of  water  is 
then  directed  on  the  part  of  the  precipitate  nearest  the  edge  of  the  filter, 
by  which  it  is  gradually  washed  towards  the   centre.     The  stream 


BY    DR.    LAUDER    BRUXTOX.  563 

should  not  be  too  strong,  nor  should  it  strike  the  filter  or  precipitate 
perpendicularly,  as  it  is  then  apt  to  scatter  the  precipitate  or  tear  the 
filter.  When  the  filter  is  nearly  full  of  water,  the  whole  should  be 
allowed  to  run  through,  and  the  washing  again  repeated. 

Washing  of  Precipitates  by  Decantation. — "When  a  precipitate  sub- 
sides quickly,  it  is  more  readily  washed  by  decantation  than  on  a  filter. 
Granular  and  gelatinous  precipitates  are  not  easily  washed  completely 
on  a  filter,  and  it  is  better  to  wash  them  as  well  as  possible  by  decanta- 
tion, and  to  finish  the  operation  on  a  filter.  In  washing  by  decantation, 
the  precipitate  is  placed  in  a  tall  beaker,  and  stirred  well  with  a  quantity 
of  water,  alcohol,  or  other  washing  liquid.  It  is  then  allowed  to  sub- 
side, and  the  supernatant  liquid  carefully  poured  off  or  removed  by  a 
syphon  (see  fig.  333)  ;  this  is  repeated  till  the  washing  is  complete.  In 
order  to  prevent  any  of  the  precipitate  being  carried  off  in  the  washing 
and  lost,  the  liquid  used  for  washing  may  be  collected  and  passed 
through  a  filter.  Any  part  of  the  precipitate  retained  by  the  filter  may 
then  be  washed,  and  the  rest  of  the  precipitate  added  to  it. 

211.  Filtration. — Filtration  is  the  separation  of  insoluble  substances 
from  liquids  bypassing  the  latter  through  a  porous  material  which  keeps 
the  former  back.  When  the  substance  to  be  removed  is  in  large  pieces, 
or  when  the  liquid  is  thick  and  viscid,  and  will  not  pass  easily  through 
paper,  it  may  be  filtered  through  linen  or  gauze.  The  linen  may  either 
be  stretched  over  the  mouth  of  a  beaker  or  placed  in  a  porcelain  strainer 
in  the  form  of  a  hollow  cone,  with  numerous  perforations  near  its  apex. 
The  removal  of  the  last  portions  of  the  liquid  may  generally  be  hastened 
by  squeezing  the  linen  either  with  the  hand  or  in  a  press  (fig.  334). 
Fine  precipitates  are  usually  separated  by  filters  of  unglazed  porous 
paper,  made  specially  for  the  purpose.  To  make  a  filter,  take  a  round 
or  square  piece  of  paper  of  the  proper  size,  and  fold  it  twice  at  right 
angles.  If  a  square  piece  has  been  used,  it  must  now  be  cut  round. 
Open  it  in  the  form  of  a  cone,  and  place  it  in  a  funnel.  If  the  funnel  is 
of  proper  form  (its  sides  sloping  at  an  angle  of  30°  to  its  axis),  the  filter 
will  fit  it  exactly.  If  it  does  not,  the  angle  at  the  apex  of  the  paper  cone 
must  be  modified.  The  filter  should  always  be  a  little  smaller  than  the 
funnel,  and  never  project  above  its  edges.  Before  pouring  in  the  liquid 
to  be  filtered,  the  paper  must  be  moistened  with  distilled  water,  alcohol, 
or  ether,  according  as  the  liquid  is  aqueous,  alcoholic,  or  ethereal.  If 
this  is  not  done,  the  first  portions  of  the  fluid  which  pass  through  are 
apt  to  be  muddy,  but  they  may  be  cleared  by  pouring  them  back  on  the 
filter  and  making  them  pass  through  a  second  time.  To  avoid  breaking 
the  filter  at  the  apex,  the  liquid  should  be  poured  on  it  so  as  to  fall  on 
its  Bides,  which  are  supported  by  the  funnel,  and  the  stream  directed  by 
a  glass  rod.  The  filtrate  is  generally  collected  in  a  beaker;  it  is  well 
to  let  the  end  of  the  funnel  touch  the  side  of  the  glass,  so  that  the  liquid 
may  run  down  it  without  splashing  If  the  filtrate  only  is  wanted,  fil- 
tration may  be  quickened  by  using  a  ribbed  or  plaited  filter.  To  make 
this,  take  a  circular  piece  of  filter  paper  and  fold  it  into  quadrants,  and 
then  into  half  quadrants,  making  all  the  folds  towards  one  side.  Then 
make  a  fold  towards  the  other  side  between  each  two  of  those  already 
made.*  aiid  push  the  paper  into  the  funnel,  pressing  the  point  down  into 
the  neck  of  the  funnel  :  then  pour  in  the  liquid,  when  it  will  open  com- 
pletely. Instead  of  this,  three  glass  rods,  bent  at  the  top  so  as  to  hook 
on  to  the  edge  of  the  funnel,  may  be  laid  inside  it  at  equal  distances 
from  each  other.  These  are  useful  both  in  quickening  the  filtration  and 
in  supporting  the  bottom  of  the  filter,  especially  when  the  funnel  is 
badly  made  and  its  tube  i-  too  wide  :it  its  junction  with  the  cone.  When 
albuminous  liquids  are  filtered  through  paper,  the  pons  become  very 
quickly  choked  up,  and  it  is  therefore  better  to  use  a  number  of  small 


564  APPENDIX. 

filters  than  one  large  one  ;  and  when  the  fluid  ceases  to  pass  through 
one  set  of  filters,  to  pour  it  into  fresh  ones. 

Filtration  by  liniment  ramp. — Filtration  may  be  much  accelerated 
by  filtering  the  liquid  into  a  partial  vacuum.  This  is  done  by  fixing  the 
tunnel  air-tighl  in  one  neck  of  a  Woulfe's  bottle,  and  exhausting  the  air 
through  the  other  by  an  ordinary  exhausting  Byringe.  It  can.  however, 
be  more  conveniently  effected  by  means  of  a  Bunsen's  water  air-pump 
(fig.  335). 

The  principle  oi  this  instrument  is  the  same  as  that  of  SprcngcTs  pump, 
with  this  difference,  that  water  is  substituted  lor  mercury.  It  consists  of 
a  wide  air-tight  tube,  through  which  water  descends  in  a  constant  stream 
to  a  depth  which  (if  it  is  desired  to  produce  a  complete  vacuum)  must 
not  be  less  than  thirty-two  feet.  Into  the  axis  of  this  tube,  close  to  its 
upper  end,  a  second  tube  of  much  smaller  bore  projects,  the  open  end 
of  which  looks  downwards,  i.  c,  in  the  direction  of  the  stream.  Through 
this  tube,  if  it  is  open,  air  is  constantly  drawn  ;  any  closed  cavity  with 
-which  it  is  in  air-tight  communication  is  rapidly  exhausted.  It  may 
thus  he  used  either  as  an  aspirator  or  as  an  air-pump.  If,  however,  the 
height  of  the  column  of  water  is  less  than  thirty-two  feet,  its  exhausting 
power  is  limited  to  the  production  of  a  diminished  pressure,  which  is 
expressed  by  the  difference  between  the  height  of  the  columnand  thirty- 
two  feet.  The  usual  way  of  employing  it  in  filtration  is  to  attach  the 
extraction  tube  11  to  a  piece  of  bent  glass  tubing,  which  passes  through 
an  India-rubber  stopper  in  one  neck  of  a  "Woulfe's  bottle,  in  the  other 
neck  of  which  a  funnel  is  fixed  in  a  similar  manner.  The  air  inside  the 
bottle  being  exhausted  by  the  air-pump,  the  fluid  is  forced  rapidly 
through  the  filter  by  the  pressure  of  the  external  atmosphere.  I  find  it 
more  convenient  to  use  a  strong  bell  jar,  with  a  tubular  opening  at  the 
top.  Into  this  opening  an  India-rubber  stopper,  which  is  perforated  for 
the  funnel  and  exhausting  tube,  is  fitted.  The  beaker  in  which  the  fil- 
trate is  to  be  received  is  placed  on  a  ground-glass  plate.  The  ground 
edge  of  the  bell  jar  having  been  smeared  with  resin  ointment,  it  is  set 
on  the  plate  in  such  a  position  that  the  funnel  is  exacttyover  the  beaker. 
The  fluid  is  then  p\>ured  into  the  filter,  and  the  air  exhausted  from  the 
bell  jar.  The  pressure  of  the  air  would  force  the  liquid  through  the 
filter  and  tear  it  away  unless  it  were  supported  in  some  way.  This  is 
done  by  taking  a  semicircular  piece  of  platinum  foil  of  suitable  size.  A 
snip  having  been  made  at  the  centre  of  the  straight  edge,  and  at  right 
angles  to  it,  the  bit  of  foil  is  heated  in  the  blowpipe  flame,  and  allowed 
to  cool.  It  can  then  be  smoothed  out,  bent  at  the  snip,  and  the  edges 
brought  together  so  as  to  overlap  each  other  slightly.  The  hollow  cone 
thus  formed  is  next  placed  in  an  iron  mould  with  a  conical  cavity,  and 
pressed  firmly  in  with  a  conical  plug.  The  funnel  used  must  be  chosen 
with  sides  sloping  at  the  proper  angle,  and  the  tube  must  not  be  too  wide 
at  the  junction  with  the  cone.  The  platinum  foil  is  placed  in  the  bottom 
of  the  funnel,  and  pressed  with  the  finger,  so  as  to  fit  the  funnel  smoothly. 
Instead  of  platinum  foil,  fine  wire  gauze  or  parchment  paper  is  some- 
times used.  The  filter  is  then  folded  and  placed  with  its  apex  resting  in 
the  platinum,  moistened  with  water,  and  pressed  gently  against  the  sides 
of  the  funnel  so  as  to  make  it  fit  tightly  to  it.  and  prevent  air  from  get- 
ting down  into  the  receiver  between  them.  Milk,  albuminous  solutions, 
and  glycerin  can  be  filtered  much  more  readily  through  porous  earthen- 
ware than  through  paper.  For  this  purpose  the  top  of  a  porous  cell, 
such  as  is  used  for  galvanic  batteries,  is  closed  by  an  India-rubber  cap 
with  two  openings.  One  of  these  is  connected  by  a  short  glass  tube  and 
strong  India-rubber  tubing  with  the  pump.  Through  the  other  a  glass 
tube  passes  nearly  to  the  bottom  of  the  c}Tinder,  and  is  closed  at  its 
upper  end  by  a  piece  of  India-rubber  tubing  and  a  strong  clip.     This 


BY    DR.    LAUDER    BRUNTON.  565 

serves  as  a  pipette  to  remove  a  little  of  the  fluid  occasionally  from  the  cell 
for  the  purpose  of  testing  it.  The  cell  is  placed  in  a  glass  cylinder,  little 
more  than  wide  enough  to  admit  it,  and  the  fluid  to  be  filtered  is  poured 
into  the  cylinder  until  it  covers  the  lower  part  of  the  India-rubber  cap. 
The  air  being  then  exhausted  from  the  cell,  the  fluid  filters  into  it  from 
the  cylinder.  Instead  of  cells,  cones  of  porous  earthenware  may  be  used 
as  filters.  A  short  piece  of  wide  India-rubber  tubing  is  stretched  over 
the  top  of  a  funnel,  and  into  its  upper  end,  which  lies  flat  across  the 
opening  of  the  funnel,  a  porous  cone  is  inserted  {see  fig.  335).  In  order 
to  keep  liquids  hot  during  the  process  of  filtration,  Plantamour's  funnel 
is  used.  This  is  a  hollow  funnel  of  copper  containing  water,  which  is 
kept  hot  by  a  flame  applied  to  a  projecting  part.  A  better  plan  is  to 
use  a  water-bath  with  a  funnel-shaped  opening  in  it  (fig.  336).  This 
has  the  advantage  that  it  may  be  kept  at  any  required  temperature  with 
the  aid  of  a  Bunsen's  regulator. 

212.  Dialysis. — Almost  all  crystalline  bodies,  with  the  notable  ex- 
ception of  haemoglobin,  pass  readily,  when  in  a  state  of  solution,  through 
animal  membranes  or  through  vegetable  parchment.  The  great  ma- 
jority of  non-crystalline  bodies,  such  as  albumin,  do  not  pass  through  at 
all,  or  only  with  very  great  difficulty.  In  this  way  the  diffusible  may 
be  separated  from  non-diffusible  substances.  Such  a  separation  is 
termed  dialysis.  Graham,  the  discoverer  of  the  process,  gave  to  the 
diffusible  bodies  the  name  crystalloids,  to  the  non-diffusible  the  name 
colloids,  as  he  thought  all  crystalline  bodies  diffused  and  all  non-crystal- 
lizable  did  not ;  but  these  names  are  open  to  objection  since  the  dis- 
covery that  hannoglobin  will  not  diffuse,  although  it  forms  crystals, 
while  peptones  diffuse,  although  they  do  not  crystallize.  Dialysis  is 
effected  by  placing  the  liquid  which  is  to  be  dialysed  in  a  cylinder,  of 
which  the  bottom  consists  of  vegetable  parchment.  This  cylinder, 
called  a  dialyser,  is  then  placed  in  a  shallow  vessel  containing  distilled 
water.  The  diffusible  substances  pass  through  the  parchment  into  the 
water,  while  the  non-diffusible  remain  behind.  Two  forms  of  dialyser 
are  in  ordinary  use.  For  dialysing  small  quantities,  bell-shaped  glass 
jars  are  used.  For  quantities  of  seven  or  eight  ounces  or  upwards,  a 
dialyser  is  employed  which  consists  of  two  gutta-percha  hoops,  one  of 
which  is  two  inches  deep,  the  other  only  one.  The  deeper  hoop  is 
Blightly  conical,  so  that  the  other  hoop  slips  over  its  smaller  end. 

Before  using  this  contrivance,  both  hoops  must  be  washed  thoroughly 
with  distilled  water.  A  piece  of  vegetable  parchment,  about  three 
inches  wider  than  the  smaller  end  of  the  deep  hoop,  must  then  be 
steeped  for  a  minute  in  distilled  water  and  stretched  over  it.  After 
applying  'he  edges  of  the  parchment  carefully  to  the  outside  of  the 
smaller  hoop,  the  larger  one  is  slipped  oyer  it,  so  as  to  fix  it  tightly. 
The  dialyser  must  next  lie  tested,  to  ascertain  that  the  parchment  is 
free  from  holes.  It  must  be  filled  to  the  depth  of  a  quarter  of  an  inch 
with  distilled  water,  and  placed  for  a  short  while  on  a  piece  of  blotting- 
paper.  If  there  are  any  holes  in  the  parchment,  the  water  will  come 
through  and  leave  a  wet  spot  on  the  blotting-paper,  in  which  case  either 
a  fresh  piece  should  be  put  on  or  the  holes  closed  up.  This  may  be 
done  by  sticking  a  piece  of  vegetable  parchment  over  the  holes  on  the 
under  surface  of  the  dialyser  with  white  of  egg,  and  then  passing  a 
smooth  hot  iron  over  the  patches.  This  done,  the  dialyser  must  be, 
again  tested.  After  having  been  ascertained  to  be  perfect,  it  maybe 
tilled  ;  the  Liquid  to  be  dialysed  must  not  cover  the  bottom  to  a  greater 
depth  than  half  an  inch.  It  must  then  be  floated  in  about  five  times  as 
much  water  as  it  contains  of  liquid  'tig.  337),  and  gently  agitated  from 
time  to  time. 

The  bell-shaped  dialysers  are  used  in  the  same  way,  but  the  paper  is 


566  APPENDIX. 

fixed  over  the  wide  end  with  a  piece  of  fine  cord,  and  the  dialyser, 
instead  of  being  floated  <>n  the  water,  is  suspended  so  thai  the  parch- 
ment is  just  below  the  surface.  This  is  effected  by  strings  which  pass 
from  its  neck  to  a  glass  rod  laid  over  the  mouth  of  a  cylindrical 
jar  containing  the  water  (fig.  338).  Diffusion  is  prompted  by  using  a 
large  Burface  of  parchment,  or  by  frequentlj  gently  shaking  the  dialyser. 
The  process  may  be  further  accelerated  by  heat  and  by  evaporation,  for 
which  purpose  the  basin  containing  the  dialyser  may  be  advantageously 
placed  in  tlic  warm  chamber  or  bath  al  a  temperature  of  37    I '. 

213.  Drying. — Glass  vessels,  in  which  substances  are  to  be  weighed, 
are  dried  by  beat.  In  the  case  of  flasks  and  tubes,  this  may  be  done  by 
warming  them  over  the  flame  of  a  spirit-lamp,  then  blowing  air  through 
them  "with  the  bellows.  For  most  purposes  the  hot-air  bath  is  used — a 
copper  vessel  either  cubical  or  cylindrical  in  shape,  and  provided  with 
a  door  or  movable  cover  (fig.  339).  It  is  heated  by  a  lamp  or  burner, 
and  must  be  furnished  with  a  thermometer,  so  fixed  as  to  indicate  the 
temperature  of  the  air  of  the  chamber.  For  all  purposes  which  re- 
quire a  temperature  not  exceeding  100°  C,  the  hot-air  bath  must  con- 
sist of  two  casings,  the  space  between  which  is  filled  with  water. 

Drying  and  Cooling  over  Sulphuric  Arid. — When  substances,  espe- 
cially hygroscopic  powders,  are  dried  in  the  air-bath  and  then  allowed 
to  cool,  they  take  up  moisture  and  gain  weight.  To  prevent  this,  they 
must  be  allowed  to  cool  under  a  bell  jar,  under  which  is  a  dish  con- 
taining sulphuric  acid  (fig.  340).  The  acid  absorbs  moisture  with 
avidity,  and  keeps  the  air  under  the  jar  dry.  The  acid  may  be  placed 
in  a  shallow  dish,  and  the  substances  to  be  dried  supported  over  it  on  a 
sheet  of  perforated  zinc,  winch  rests  on  the  edges  of  the  dish  or  on  a 
small  tripod.  Another  method  is  to  put  the  acid  in  a  beaker,  covered 
with  a  ground-glass  plate  greased  at  the  edges,  and  to  supporl  the  cru- 
cible on  a  leaden  support  ;  the  support  is  made  of  a  bit  of  strong  leaden 
wire  by  bending  one  end  of  it  into  a  circle  which  lies  at  the  bottom  of 
the  beaker,  and  the  other  end  into  a  smaller  circle  which  rises  above 
the  surface  of  the  acid  and  holds  the  crucible.  To  prevent  dried  hydro- 
scopic substances  from  taking  up  moisture  during  weighing,  they 
should  not  be  placed  in  an  open  vessel,  but  inclosed  between  two  watch- 
glasses  held  together  by  a  spring. 

When  it  is  desired  to  dry  substances  without  the  aid  of  heat,  they  are 
to  be  placed  under  the  receiver  of  an  air-pump  and  over  sulphuric  acid. 
as  just  mentioned. 

Precipitates  maybe  rapidly  dried  by  supporting  the  funnel  containing 
them  over  a  very  small  flame  by  means  of  a  beaker  with  the  bottom 
out.  a  triangle  of  iron  wire  and  a  piece  of  wire  gauze,  arranged  as  in 
fig.  041. 

214.  Ignition. — Substances  are  exposed  to  a  red  beat  in  order  to  dry 
them  thoroughly,  to  drive  away  volatile  matters,  or  to  burn  off  organic 
constituents,  and  allow  the  fixed  inorganic  solids  to  fie  determined.  A 
small  quantity  of  a  substance  may  be  ignited  on  a  piece  of  platinum 
foil  or  in  a  platinum  spoon,  larger  quantities  in  porcelain  or  platinum 
crucibles.  Platinum  vessels  should  not  lie  used  if  the  substance  to  be 
ignited  contains  iodine,  bromine,  phosphorus,  or  easily  reducible 
metals,  such  as  copper,  lead.  sHver,  gold,  or  tin.  Wjien  precipitates 
collected  in  a  filter  are  ignited,  they  must  be  first  carefully  dried.  The 
crucible  is  then  to  be  placed  on  a  piece  of  glazed  paper,  the  precipitate 
loosened  from  the  filter  by  rubbing  the  sides  together,  and  then  shaken 
gently  into  the  crucible.  The  tiller  is  then  either  (bided  and  placed  in 
the  crucible,  or  it  is  set  tire  to  and  held  over  it  by  a  pair  of  forceps,  so 
that  the  ashes  may  fall  into  it.  Any  ashes  or  precipitate  that  has  fallen 
on  the  paper  having  been  collected  and  added  to  the  rest,  the  crucible 


BY    DR.    LAUDER    BRUNTON.  567 

is  placed  in  a  triangle  of  platinum  wires  stretched  on  a  larger  one  of 
iron  wire  (fig.  342),  and  heated  over  a  Bnnsen's  lamp.  The  cover 
should  be  laid  on  the  crucible  at  first  to  prevent  any  loss,  and  the  heat 
raised  very  gradually.  The  cover  may  be  removed  during  part  of  the 
process  to  allow  freer  access  of  air,  but  towards  the  end  it  should  again 
be  replaced  so  that  the  heat  within  the  crucible  may  become  greater. 
With  the  same  view,  the  blowpipe  flame  may  be  substituted  for  that 
of  the  Bunsen's  burner.  The  crucible  is  then  allowed  to  cool  somewhat 
on  the  triangle,  but  while  still  warm  must  be  placed  over  sulphuric 
acid,  and  left  there  till  cold.  The  weight'of  ash  left  by  a  good  filter  is 
very  inconsiderable  ;  but  it  may  be  ascertained  by  burning  a  dozen 
filters  and  dividing  the  weight  of  the  ash  by  the  number.  Filters  may 
be  almost  completely  deprived  of  ash  by  extracting  them  with  dilute 
hydrochloric  acid,  and  washing  them  with  water  till  the  acid  reaction 
completely  disappears. 

215.  Weighing. — The  balances  most  useful  in  a  plrysiological  labora- 
tory are  a  fine  analytical  balance  to  carry  100  grammes  in  each  pan,  and 
turn  easily  with  half  a  milligramme  or  less,  and  a  large  balance  to  carry 
seventy  kilogrammes,  aud  turn  with  a  few  grammes.  Fine  balances 
are  always  protected  by  glass  covers,  to  prevent  the  access  of  dust  and 
protect  the  instrument  from  draughts  of  air,  etc.  Inside  this,  a  vessel 
containing  chloride  of  calcium  is  often  placed  to  keep  the  air  dry.  The 
doors  of  the  case  should  be  only  opened  when  the  substance  or  weights 
are  to  be  adjusted,  and  should  be  closed  while  the  beam  is  oscillating. 
It  is  convenient  to  lay  the  weights  on  a  sheet  of  paper  on  the  floor  of 
the  balance,  and  to  mark  the  weight  of  each  on  that  part  of  the  paper 
where  it  lies.  They  must  never  be  touched  with  the  fingers,  only  with 
forceps.  It  is  advisable  always  to  place  the  weights  in  the  same  pan 
(the  right)  of  the  balance,  aud  the  substance  to  be  weighed  in  the 
other.  The  placing  of  heavy  weights  on  a  fine  balance  should  be 
avoided,  even  though  they  may  not  exceed  the  weight  which  the  instru- 
ment is  constructed  to  carry.  Nothing  should  be  placed  on  the  pans  or 
taken  from  them  while  the  beam  is  oscillating.  It  is  not  necessary  to 
wait  each  time  till  the  index  stops  moving  in  order  to  see  whether  there 
is  any  difference  between  the  weights  in  the  pans  ;  for  this  is  ascer- 
tained much  more  axactly  by  observing  whether  the  index  oscillates 
farther  on  one  side  of  the  zero  mark  than  ori  the  other,  than  by  noticing 
its  position  when  at  rest.  After  weighing,  add  together  the  weights 
which  are  absent  from  their  places  on  the  paper.  Note  down  the  weight 
"/  <///rv,  and  cheek  it  by  adding  the  weights  together  as  they  are  lifted 
from  the  pan  and  replaced.  No  weight  should  ever  be  allowed  to  remain 
on  the  balance  after  weighing.  Substances  are  generally  weighed  in 
watch-glasses,  small  crucibles  or  small  flasks.  These  may  be  either 
weighed  separately,  and  their  weight  deducted  from  the  total  weight,  or 
they  may  lie  counterpoised.  To  save  the  trouble  of  weighing  them  each 
lime,  they  may  lie  carefully  weighed  once  for  all,  and  their  weight  noted 
and  marked  on  them  with  a  diamond,  or,  if  they  arc  of  porcelain,  in 
ink.  When  a  crucible  with  its  lid  is  used,  it  is  usual  to  put  correspond- 
ing marks  on  the  crucible  and  its  lid,  so  that  the  same  may  be  used  each 
time.  Counterpoises  may  he  made  in  various  ways.  The  most  con- 
venient is  to  choose  a  piece  of  brass  of  about  the  size  of  the  brass  weight 
which  corresponds  most  closely  to  the  weight  of  the  vessel  to  be  coun- 
terpoised, and  reduce  if  by  careful  filing  till  the  weights  are  exactly 
equal.  If  only  required  for  temporary  use,  a  pill-box  partly  filled  with 
small  shot  will  suffice. 

216.  Specific  Gravity. — The  specific  gravity  of  a  solid  or  liquid  is 
it-  weight  compared  with  that  of  an  equal  bulk  of  distilled  water. 
Water  and   other  liquids,   however,  shrink  when  cooled,  and  expand 


568  APPENDIX. 

when  heated,  so  that  the  weight  of  a  given  bulk  varies  with  the  tempe- 
rature.    It'  a  vessel  containing,  for  example,  a  cubic  inch  is  filled  with  a 

fluid  at  a  moderate  temperature  and  cooled,  the  liquid  will  shrink,  and 
more  must  be  poured  in  to  till  up  the  space.  If,  on  the  contrary,  it  be 
wanned,  the  liquid  will  run  over.  The  weight  of  the  cubic  inch  of  cold 
liquid  will  be  greater  than  that  of  the  liquid  at  the  original  temperature 
by  the  quantity  poured  in,  while  that  of  the  hot  liquid  will  be  less  by 
that  which  has  run  over.  It  is  therefore  absolutely  necessary  to  com- 
pare the  weights  of  bodies  at  the  same  temperature.  Specific  gravities 
are  in  this  country  estimated  "at  15    0.  or  GO-  F. 

Specific  Gravity  of  Liquids. — The  specific  gravity  of  a  liquid  maybe 
ascertained  by  the  use  of  the  specific  gravity  bottle,  the  hydrometer,  or 
specific  gravity  beads. 

The  Sjjectfic  Gravity  Bottle. — This  is  a  small  bottle  which  contains  a 
known  volume  of  liquid  ;  one  form  of  bottle  (fig.  343)  contains  its  pro- 
per quantity  when  it  is  filled  perfectly  full,  another  form  (fig.  344)  when 
filled  up  to  a  mark  on  the  neck,  which  is  long  and  thin.  The  bottle  hav- 
ing been  charged  with  the  liquid,  of  which  the  specific  gravity  is  to  be 
determined,  the  weight  of  its' contents  is  determined  by  the  balance,  for 
which  purpose  it  must  first  be  counterpoised.  The  quotient  obtained  by 
dividing  the  weight  of  the  liquid  by  the  weight  of  the  same  bulk  of 
water  at  the  same  temperature  is  its  specific  gravity.  It  is  difficult  to 
fill  an  ordinary  bottle  completely  and  to  put  in  the  stopper  without  get- 
ting in  an  air-bubble,  which  would  of  course  alter  the  weight  of  the 
contents  and  so  give  false  results.  To  obviate  this  difficulty,  the  stop- 
per of  a  specific  gravity  bottle  has  a  hole  bored  up  through  its  middle, 
so  that  when  the  bottle  is  filled  and  the  stopper  put  in,  any  air  or  fluid 
that  may  be  present  in  the  neck  passes  up  through  the  hole,  and  thus 
both  the  bottle  and  the  hole  in  the  stopper  are  completely  filled  with 
fluid.  Before  weighing  the  empty  bottle  or  making  a  counterpoise  for 
it,  it  must  be  thoroughly  dried.  Specific  gravity  bottles  of  this  kind 
are  usually  constructed  to  contain  from  50  to  100  grammes  of  distilled 
water  at  15°  C.  Counterpoises  are  always  sold  with  them.  Before 
using  them,  the  accuracy  both  of  the  counterpoise  and  of  the  capacity 
of  the  bottle  must  be  tested.  For  the  latter  purpose,  the  bottle  must  be 
filled  and  then  immersed  in  a  beaker  containing  distilled  water  at  a  tem- 
perature a  few  degrees  higher  than  15°  C,  and  allowed  to  remain  until 
a  thermometer  standing  in  the  water  indicates  that  the  required  tempe- 
rature has  been  reached.  The  bottle  must  then  be  removed  from  the 
beaker  and  weighed  against  the  counterpoise,  its  outside  having  been 
first  carefully  wiped  dry.  The  weight  is  that  of  the  distilled  water 
contained  in  the  bottle  at  15°  C.  In  weighing  the  contents  of  the  bot- 
tle when  charged  with  any  liquid  of  which  the  specific  gravity  is  to  be 
determined,  the  same  method  is  to  be  followed,  with  the  exception  that 
the  bottle  must  not  be  completely  immersed  in  the  liquid  contained  in 
tin'  beaker.  If  then  w  indicate  the  weight  of  the  water  and  w'  that  of 
the  same  volume  of  the  other  liquid  at  the  same  temperature,  its  specific 
gravity  =^,'. 

Sometimes  it  is  difficult  to  get  a  sufficient  quantity  of  liquid  to  fill  the 
specific  gravity  bottle  just  described.  When  this  is  the  case,  a  specific 
gravity  bottle  may  be  made  out  of  a  test-tube,  by  drawing  it  out,  as  in 
the  accompanying  figure  (fig.  345),  and  then  flattening  the  bottom  so  as 
to  make  it  stand  by  heating  it  and  pressing  it  against  a  piece  of  iron. 
A  scratch  is  to  be  made  on  the  narrow  part  of  the  neck,  up  to  which 
the  bottle  is  to  be  filled  with  water  at  15 :  C  and  weighed  against  a 
counterpoise  as  before.  In  all  other  respects  the  procedure  is  that  which 
has  been  already  described. 


BY    DR.    LAUDER    BRUNTON.        •  569 

The  Hydrometer. — The  hydrometer  is  an  elongated  glass  bulb  which 
is  weighed  at  one  end  so  as  to  make  it  float  upright,  and  is  prolonged  at 
the  other  end  into  a  stem,  graduated  in  such  a  manner  that  the  number 
of  the  division  up  to  which  the  instrument  sinks  expresses  the  specific 
gravity  of  the  liquid  in  which  it  is  placed.  As  every  instrument  reads 
accurately  only  at  the  temperature  for  which  it  is  constructed,  the 
liquid  must  be  brought  to  the  proper  temperature  before  the  instrument 
is  used.  In  using  the  hydrometer,  the  liquid  must  be  placed  in  a  cylin- 
drical glass  vessel,  deep  enough  and  wide  enough  to  allow  the  instru- 
ment to  float  freely  in  it  without  coming  in  contact  with  the  sides  or 
bottom.  The  froth,  if  any,  is  then  to  be  removed  from  the  surface  with 
a  piece  of  blotting-paper,  and  the  hydrometer  allowed  gently  to  sink 
into  the  liquid.  The  mark  on  the  scale,  which  coincides  with  its  sur- 
face, indicates  the  specific  gravity.  To  read  this  correctly,  the  eye 
must  be  brought  to  a  level  with  the  surface  of  the  liquid.  When  this 
is  the  case,  the  surface  presents  the  form  of  a  meniscus,  assuming  the 
aspect  of  an  ellipse  when  the  eye  is  either  raised  or  lowered.  To  insure 
accuracy,  the  reading  should  be  repeated  once  or  twice,  the  hydrometer 
being  down  in  the  liquid  between  each  two  observations. 

Specific  Gravity  of  Solids. — The  specific  gravity  of  a  solid  mass,  the 
substance  of  which  is  insoluble,  is  ascertained  by  weighing  it  first  in  air 
and  then  in  water.  The  difference  between  these  weights  is  equal  to 
the  weight  of  its  own  bulk  of  the  water  which  it  displaces.  The  specific 
gravity  is  therefore  got  by  dividing  the  weight  of  the  solid  in  air  by  the 
difference  between  its  weight  in  air  and  water.  The  weight  of  solids 
may  also  be  ascertained  by  immersing  them  in  fluids  of  known  density 
till  thej'-  float.  Thus  the  best  way  of  ascertaining  the  specific  gravity  of 
the  substance  of  the  brain,  or  any  other  organ,  is  to  prepare  a  graduated 
series  of  solutions  of  common  salt  of  different  densities,  and  to  immerse 
the  solid,  first  in  one,  and  then  in  another,  till  a  solution  is  found  in 
which  it  floats  indifferently  at  any  height. 

217.  Volumetrical  Analysis. — For  volumetrical  analyses,  measuring 
flasks,  measuring  glasses,  pipettes,  burettes,  and  other  accessory  appa- 
ratus are  required. 

Measuring  Flasks. — These  flasks,  of  the  form  shoAvn  in  fig.  346,  are 
used  for  dissolving  substances  for  the  preparation  of  standard  solutions, 
etc.  They  should  have  tolerably  wide  mouths,  and  be  furnished  with 
well-fitting  stoppers,  so  that  they  may  be  shaken  without  risk  of  loss. 
The  graduation  mark  should  be  just  below  the  middle  of  the  neck. 
Flasks  are  used  of  capacities  varying  from  100  centimetres  to  a  litre. 
Graduated  cylinders,  such  as  that  shown  in  fig.  347,  generally  called 
test-mixers,  are  used  for  the  same  purpose. 

l'ipcttes.—h.  pipette  is  a  glass  tube  of  the  shape  shown  in  fig.  348,  and 
when  tilled  up  to  the  mark  on  the  neck  it  should  deliver  the  exact  quan- 
tity «)!'  fluid  which  is  marked  upon  it.  Some  pipettes  are  graduated  so 
as  to  let  the  exact  quantity  run  out  by  its  own  weight  ;  others,  to  de- 
liver the  right  amount  only  when  the  liquid  is  blown  forcibly  out.  The 
former  are  to  be  preferred.  Another  kind  of  pipette  is  graduated  along 
the  greater  part  of  its  length,  so  as  to  deliver  different  quantities  at  will, 
but  it  ,is  not  so  accurate  as  the  others.  In  using  pipettes,  the  liquid  to 
lie  measured  is  to  be  put  into  a  test-glass  or  small  beaker  ;  the  lower 
end  of  the  pipette  is  then  immersed  in  the  liquid,  which  is  to  be  sucked 
up  till  it  stands  somewhat  above  the  mark  on  the  neck  of  the  pipette. 
Tin  upper  cad  of  tiie  pipette  must  then  be  quickly  covered  with  the 
moistened  tip  of  tin'  forefinger,  so  as  to  prevent  the  liquid  from  flowing 
out.  'lie-  mark  on  the  neck  is  next  brought  to  a  level  with  the  eye,  and 
the  tip  of  the  finger  gently  raised  so  as  to  allow  the  liquid  to  escape  slowly 
till  it  stands  opposite  the  mark.     It  is  then  allowed  to  run  out  into  a  clean 


570  APPENDIX. 

beaker,  and  the  last  few  drops  removed  from  t  lie  point  of  the  pipette  by 
touching  it  againsl  the  Bide  of  the  beaker. 

Burettes.-  -These  are  used  for  delivering  standard  solutions.  There 
arc  several  forms  of  burette,  but  the  most  convenient  is  that  of  Mohr. 
It  consists  of  a  graduated  tube,  to  whose  lower  end  an  india-rubber  tube 
is  attached,  which  can  be  opened  and  shut  by  a  spring  clip  (fig.  349),  so 
that  the  operator  can  lei  the  solution  rim  out  or  stop  it  at  will.  The  bu- 
rette is  supported  in  an  upright  position  on  a  stand  made  for  the  purpose 
(fig.  852).  To  prevent  dust  getting  in,  a  polished  marble  should  be 
placed  on  its  upper  end.  In  many  cases  the  spring  clip  answers  well, 
but  when  nitrate  of  mercury  is  used  it  attacks  the  clip,  and  bichromate 
of  potash  destroys  the  India-rubher.  For  such  liquids  a  burette  fur- 
nished with  a  glass  stopcock  is  to  be  preferred.  A  burette  should  he 
filled  by  allowing  the  liquid  to  How  gently  into  it  while  it  is  held  in  an 
inclined  position  in  the  hand  till  it  stands  above  the  zero  mark.  The  in- 
strument is  then  replaced.  If  any  air-bubbles  are  present,  they  musl  be 
allowed  to  break,  or  removed  by  a  glass  rod.  The  solution  is  then  al- 
lowed to  flow  out  till  its  level  corresponds  to  the  zero  mark  on  the  burette. 

Eulesfor  Reading  Burettes  and  other  Graduated  Instrument*  used  in 
Volumetrical  Analysis. — When  liquid  is  contained  in  a  narrow  tube,  its 
surface  is  higher  at  the  edges  where  it  touches  the  ulass  than  elsewhere  ; 
and  if  we  examine  the  curved  surface  by  transmitted  light,  it  seems  to 
be  formed  of  several  zones  or  bands,  the  lowest  of  which  is  dark  (tig. 
850).  To  avoid  errors  and  uncertainty,  the  under  border  of  the  dark 
zone  is  always  regarded  as  indicating  the  level  at  which  the  liquid  stand-. 
In  reading,  the  eye  must  of  course  be  exactly  level  with  the  surface, 
otherwise  the  reading  will  be  cither  too  high  or  too  lowr.  The  under 
surface  of  the  liquid  is  incur  easily  seen  if  a  card,  with  its  under  half 
blackened,  while  its  upper  half  remains  white,  be  held  behind  the  liquid, 
so  that  the  division  between  the  black  and  white  parts  is  about  one-eighth 
of  an  inch  below  its  surface.  The  lower  surface  of  the  liquid  then  seems 
to  be  bounded  by  a  sharp  black  line  (Sutton).  Burettes  may  be  read 
very  easily  and  with  great  accuracy  by  using  Erdmann's  float  (fig.  :i"i1  . 
This  is  an  elongated  glass  bulb,  'weighted  with  mercury  at  its  lower  end. 
so  that  it  floats  upright.  Its  diameter  being  a  very  little  less  than  the 
calibre  of  the  burette  which  contains  it,  it  moves  freely,  but  at  the  same 
time  steadily,  up  and  clown.  A  horizontal  mark  round  its  middle  is 
taken  as  indicating  the  height  at  which  the  liquid  stands,  the  absolute 
height  being  disregarded. 

Litmus  Solution. — The  solution  used  in  the  neutralization  of  albumi- 
nous liquids  is  prepared  by  dissolving  a  little  litmus  in  distilled  water, 
decanting  the  liquid  from  the  sediment,  and  diluting  it  as  required.  For 
determinations  of  the  strength  of  acid,  the  litmus  solution  is  made  by 
putting  10  grammes  of  solid  litmus  into  half  a  litre  of  distilled  water,  let- 
ting it  stand  for  a  few  hours  in  a  warm  place,  decanting  the  clear  fluid, 
adding  a  few  drops  of  dilute  nitric  acid  so  as  to  produce  a  violet  color, 
and  preserving  it  in  an  open  bottle  with  a  narrow  neck.  If  the  color 
should  at  any  time  partially  disappear,  it  may  be  restored  by  exposing  the 
liquid  to  the  air  in  an  open  bottle  (Sutton). 

Volumetric  Solution  of  Soda. — Fill  a  burette  with  solution  of  soda, 
and  cautiously  drop  thisinto  0.3  grammes  of  purified  oxalicacid  in  crys- 
tals, quite  dry  but  not  effloresced,  dissolved  in  about  70  c.  c.  of  distilled 
Water,  until  the  acid  is  exactly  neutralized,  as  indicated  by  litmus.  Note 
the  number  of  grain  measures  (n)  of  soda  solution  used,  and  having 
then  introduced  900  c.  c.  of  it  into  a  graduated  jar,  augment  this  quantity 

900x140 
by  the  addition  of  water  until  it  becomes  cc     If,  for  example, 

n 

?i=93,  the  900  cub.  cent,  should  be   augmented  to  !      *        =907.7 

Jo 


BY    DR.    LAUDER    BRUNTON.  571 

cub.  cent.  100  cub.  cent,  contain  ^th  of  an  equivalent  in  grammes  (4 
grammes)  of  hydrate  of  soda,  and  will  neutralize  ^th  of  an  equivalent 
in  grammes  of  an  acid. 

Soda  solution  for  estimating  the  acidity  of  gastric  juice  is  made  by  di- 
luting 100  c.  c.  of  the  above  solution  to  the  bulk  of  a  litre. 

218.  Polariscope. — There  are  several  organic  substances  Avhose 
solutions  possess  the  power  of  circumpolarization,  i.  e.,  of  rotating  to  one 
side  or  another  the  plane  of  polarization  of  a  ray  of  polarized  light  passing 
through  them.  Some  of  them,  such  as  glucose,  cane  sugar,  and  tartaric 
acid,  turn  it  to  the  right  hand,  while  others,  such  as  albumin,  uncrystal- 
lizable  sugar,  and  oil  of  turpentine,  turn  it  to  the  left.  As  the  amount  of 
rotation  increases  in  proportion  to  the  concentration  of  the  solution  and 
the  thickness  of  the  stratum  through  which  the  ray  passes,  if  is  easy  to 
ascertain  the  quantity  of  a  substance  held  in  solution  by  simply  observing 
the  extent  to  which  a  ray  is  rotated  in  passing  through  a  stratum  of  a  de- 
finite thickness.  The  apparatus  used  for  this  purpose  is  shown  in  fig.  353. 
It  consists  of  a  stand  in  which  are  placed  two  Xieol's  prisms,  a  and  b. 
The  prism  b  is  fixed,  but  that  at  a  is  movable,  and  the  extent  to  which 
it  is  rotated  is  indicated  on  a  graduated  circular  disk  s  s  by  an  index  z. 
When  the  two  prisms  are  placed  exactly  in  the  same  position,  the  ray, 
which  has  been  polarized  by  b  passes  readily  through  «,  and  the  field  of 
vision  of  an  observer,  looking  into  the  instrument  at  «,  is  illuminated. 
As  a  is  turned  round  on  its  axis,  the  field  becomes  dimmer  and  dimmer 
till  the  two  prisms  are  turned  crosswise  to  each  other,  when  the  polar- 
ized ray  by  b  is  entirely  stopped  by  a,  and  the  field  consequently  be- 
comes quite  dark.  At  this  time  the  index  stands  at  zero.  If  a  glass 
tube,  containing  a  solution  of  sugar  or  albumin,  is  then  placed  in  the 
space  oo,  the  polarized  ray  will  pass  through  it,  and  in  doing  so  will 
have  its  plane  of  polarization  more  or  less  rotated,  so  that  it  will  no 
longer  be  entirely  stopped  by  the  prism  a.  In  order,  therefore,  to  stop 
it  again  and  produce  a  dark  field,  this  prism  must  be  rotated  to  a  corre- 
sponding degree,  and  the  extent  of  rotation  is  read  off  on  the  graduated 
disk.  As  it  is  difficult  to  determine  exactly  the  position  of  a,  at  which 
the  field  is  darkest,  some  additions  have  been  made  to  this  instrument 
by  Boleil  and  Ventzke,  which  make  their  saccharimeter  more  complica- 
ted, but  greatly  increase  its  exactitude.  The  first  of  these  is  a  plate  of 
quartz,  q,  composed  of  two  pieces,  whose  line  of  junction  is  exactly  in 
the  middle  of  the  field  of  vision.  One  piece  rotates  light  to  the  right 
hand,  while  the  other  turns  it  to  the  left.  When  a  solution  of  sugar 
is  placed  in  the  space  o  o,  it  increases  the  action  of  that  half  of  the  plate 
which  rotates  to  the  right,  and  lessens  the  action  of  the  other  halfwhich 
rotates  to  the  left,  and  the  two  halves  of  the  field  of  vision  become  of  a 
different  color.  This  difference  can  be  removed  by  turning  the  prism 
a.  but  this  is  more  easily  effected  by  means  of  the  compensator  /'.  The 
chief  parts  of  tins  are  figured  separately.  It  consists  of  two  equal 
prisms  (rand  r')  of  left  -handed  quartz,  whose  surfaces  (c  and  c')  are 
ent  perpendicularly  to  the  optic  axis  of  the  crystal.  Taken  together 
they  form  a  plate  bounded  by  parallel  surfaces,  and  they  can  be  made 
to  slide  on  one  another  by  means  of  a  rack  and  pinion,  »,  so  as  to  in- 
crease or  diminish  its  thickness  at  will.  One  of  the  frames  in  which 
these  is  fixed  has  a  Male,  /.  ami  the  other  a  vernier,  n.  When  the  zero 
of  this  corresponds  to  the  zero  on  the  scale,  the  left-handed  rotation  of 
the  two  prisms  is  compensated  by  a  plate  of  right-handed  quartz,  ]'.  and 
the  field  then  appea rs  of  an  uniform  color,  but  as  soon  as  the  prions  are 

moved  this  compensation  ceases,  and  the  two  halves  become  differently 
colored.     The  Name  effecl  is  produced  by  putting  a  solution  of  sugar 

into  o  o.  The  screw  ''  i-i  then  turned  fill  the  effect  of  tin-  sugar  is  counter- 
balanced and  the  amount  of  rotation  read  off  on  the  scale.      At  this  end, 


K79 


APPENDIX. 


a,  is  a  telescopic  adjustment,  to  enable  the  division  between  the  two 
halves  of  the  quartz  to  be  clearly  seen. 

In  using  this  instrument,  the  end  h  should  be  placed  opposite  the 
brightest  part  of  a  lamp  Mame,  and  it  is  advisable  to  cover  the  flame 
with  an  earthenware  cylinder  having  an  aperture  which  just  admits 
the  end  of  the  saceharimeter,  so  as  to  shut  off  all  light  excepl  that  which 
passes  through  the  instrument.  The  zero  of  the- vernier  having  been 
placed  opposite!  that  of  the  scale,  the  operator  looks  into  the  end  <(,  and 
adjusts  the  telescope  till  the  dark  line  in  the  centre  of  the  field  is  clearly 
defined.  If  the  two  sides  of  the  field  are  of  exactly  the  same  tint,  he 
may  proceed  with  the  operation,  but  if  they  are  not,  he  must  adjust 
them  by  means  of  a  screw  and  key,  which  are  not  represented  in  the 
engraving.  The  tube  is  then  to  be  filled  with  the  fluid  to  lie  examined, 
and  its  end  closed  by  a  piece  of  glass  and  a  metal  cap,  which  should 
not  be  screwed  too  tightly.  The  fluid  must  be  transparent,  and  as 
colorless  as  possible.  A  light  yellow  color  does  not  interfere  with  the 
accuracy  of  the  determination,  but  a  red  or  brown  color  impairs  it 
seriously.  Three  tubes,  1,  2,  and  h  a  decimetre  in  length,  are  generally 
supplied  with  each  instrument,  and  the  longer  the  tube  used,  the  more 
exact  is  the  determination.  Dark  fluids  may  be  examined  in  the 
shorter  tubes,  but  if  very  dark  they  should  be  diluted  before  examina- 
tion. The  tube  is  then  placed  in  the  space  o  o,  and  the  rack  r  is  turned 
till  the  two  halves  of  the  field  present  exactly  the  same  tint.  By  turn- 
ing the  prism  a,  different  colors  of  the  field  may  be  obtained  ;  a  pale 
rose  color  is  that  in  which  differences  of  the  two  halves  can  be  most 
readily  observed.  The  distance  to  which  the  zero  of  the  vernier  has 
been  moved  from  that  of  the  scale  to  one  or  other  side,  indicates  the 
amount  of  dextro-  or  loevo-rotation.  The  compensator  is  so  graduated 
that  each  degree  of  the  scale  corresponds  to  one  gramme  of  sugar  or 
albumin  in  130  cub.  cent,  of  fluid  when  a  tube  one  decimetre  long  is 
used.  When  tubes  of  a  different  length  are  employed,  the  number  of 
degrees  must  be  divided  by  the  length  of  the  tube  in  order  to  find  out 
the  strength  of  the  solution.  As  sugar  and  albumin  rotate  the  rays  in 
a  different  direction,  their  amount  cannot  be  determined  when  both  are 
present  in  a  solution,  the  instrument  then  indicating  merely  the  differ- 
ence between  their  rotating  power.  In  such  a  case  the  albumin  must 
be  removed  and  the  amount  of  sugar  determined.  The  difference 
between  the  rotation  caused  by  the  sugar  alone  and  the  sugar  and 
albumin  together,  will  then  of  course  give  the  rotation  due  to  albumin. 
This  instrument  may  also  be  used  for  distinguishing  between  substances, 
such  as  albuminous  bodies,  which  nearly  resemble  each  other  in  their 
general  characters  and  reactions,  but  have  different  powers  of  rotation 
or  specific  rotation.  The  specific  rotation  of  a  substance  is  the  extent 
to  which  a  solution  of  one  gramme  in  one  cubic  centimetre,  contained 
in  a  tube  one  decimetre  long,  will  rotate  a  ray  of  light  passing  through 
it.  To  indicate  rotation  of  light  to  the  right,  a  -f-  is  prefixed  to  the 
number  of  degrees  through  which  the  beam  is  turned,  and  a  —  to  indi- 
cate rotation  to  the  left.  The  specific  rotation  of  sugar  is  +  56°  ;  that 
of  albumin  —  5G°.  To  find  out  the  specific  rotation  of  any  substance 
with  the  saceharimeter,  the  following  formula  is  used  (Hoppe- 
Seylerj  :  — 

•^  pi 

( a  j  is  the  usual  symbol  for  the  specific  rotation  for  yellow  light,  a  is 
the  rotation  indicated  on  the  scale,  p  the  weight  of  the  substance  in 
grammes  contained  in  100  cub.  cent,  of  the  solution,  and  I  the  length 


BY  DR.   LAUDER   BRUNTOX.  573 

of  the  tube  employed.  The  specific  rotation  of  different  albuminous 
bodies  for  yellow  light,  as  given  by  Hoppe-Seyler  for  serum  albumin, 
is  —  56°,  and  for  egg  albumin  —  35°.  5.  The  conversion  of  serum  albumin 
into  acid  albumin  by  phosphoric  or  acetic  acid  increases  its  specific 
rotation  to  —  71°,  and  a  solution  in  hydrochloric  acid  has  a  rotation 
of — 78°.  7.  Serum  albumin,  treated  with  caustic  potash,  has  a  rotation 
of— 86°;  egg  albumin,  — 47°;  and  coagulated  egg  albumin,  treated  in 
the  same  way,  —  58°. 8,  for  yellow  light. 


574  LIST    OF    INSTRUMENTS,    ETC. 


The  Instruments  and  Apparatus  referred  to  in 
this  Work  may  be  obtained  from  Jas.W.  Queen 
&  Co.,  Opticians,  924  Chestnut  St.,  Philad'a. 


I.  HISTOLOGY, 


Microscopes.— "Continental"  Models  of  various  makes;  English  and 
American  Models,  including  Bausch  &  Lomb,  Queen's  Acme, 
Crouch,  Zentmayer,  Beck,  or  any  other  spe'cial  make  preferred. 

Warm  Stages,  Injecting  Apparatus,  Syringes  and  Oanulse, 
Fine  Scissors  and  Forceps,  Spring  Clips,  etc. 

Hatching  Oven. 

Soluble  Prussian  Blue. 

Gelatin,  plain,  and  prepared  for  Injecting. 

Chemicals. 

II.  PHYSIOLOGY  OF  THE  CIRCULATION  AND  RESPIRATION. 

Gas  Pumps.— Made  by  Alvergniat  et  Freres,  Dr.  Geissler,  and  Cam- 
bridge Scientific  Instrument  Co. 

Sprengel's  Pump,  Frankland  and  Macleod's  Apparatus, 
Recipients  and  other  Apparatus  for  Analysis  of  Blood  Gases. 
— Manufactured  by  Dr.  Geissler. 

Kymograph,  Arterial  Schema,  Cardiograph,  Marey's  Tym- 
pana and  Levers,  Recording  Stethometer,  Czermak's 
Rabbit  Support,  Manometer,  and  Support  for  Coats' 
Apparatus,  Delicate  Thermometers,  Aneurism  Nee- 
dles, Blunt  Hooks,  Clips,  Screw  Clamps,  and  other 
Instruments. — Made  by  C.  Verdin,  Cambridge  Scientific  Instru- 
ment Co.,  and  Hawksley. 

Bernard's  Holder. — Manufactured  by  Cambridge  Scientific  Instru- 
ment Co. 


LIST  OF   INSTRUMENTS,  ETC.  575 

Pick's    Spring    Kymograph.— Made  by  Verdin,  and    Cambridge 

Scientific  Instrument  Co. 
Sphygmograph. — Made  by  C.  Verdin. 
Bunsen's  Compressed  Air  Water-Pump. — See  De  Saga  and  Dr. 

Geissler. 
Calorimeter.— Salleron. 

III.  PHYSIOLOGY  OF  THE  NERVOUS  SYSTEM. 

Galvanometers  and  Shunts,  Du  Bois  Reymond's  Induction 
Apparatus,  Rheochord,  Commutator,  Wippe,  and 
other  Electrical  Apparatus. — Manufactured  by  Elliott  Bros.,  J. 
Carpentier,  Hartmann  &  Co.,  and  M.  Th.  Edelmann. 

Moist  Chamber,  Marking  Key,  Marey's  Myograph. — Made 
by  Cambridge  Scientific  Instrument  Co.,  Hawksley,  Verdin,  etc. 

Batteries. — Jas.  W.  Queen  &  Co. 

IV.  DIGESTION  AND  SECRETION. 

Gastric  and  other  Canulse. — Made  by  Cambridge  Scientific  Instru- 
ment Co.,  Verdin,  and  Hawksley. 

Bunsen's  Regulator.— Jas.  W.  Queen  &  Co. 

"Water-Baths  for  Digestion. — Jas.  W.  Queen  S-  Co. 

Beakers,  Test-Tubes  and  Glass  Apparatus. — Jas.  W.  Queen 
cfr  Co. 

Chemical  Apparatus. — Jas.  W.  Queen  &  Co. 

Soleil's  Polarization  Apparatus,  as  adapted  by  Ventzke,  for  the 
Quantitative  Determination  of  Grape  Sugar  and  Albumin  :  also 
Polariscopes,  by  Laurent  and  Duboseq. — Jas.  W.  Queen  <f* 
Co.,  Agents  in  North  America. 

Apparatus  for  Volumetric  Analysis  and  Titrated  Solu- 
tions.— Jas.  W.  Queen  &  Co. 


INDEX. 


Absolute  arterial  pressure,  Measure- 
ment of,  22o 
Absorption  by  the  liver,  505 
internal,  by  veins,  296 
by  veins  and  lymphatics,  293 
Accelerator,  Nerves  of  heart,  286 
Acetic  acid,  Action  of,  on  fibrous  tis- 
sues, 47 
Acid  albumin,  or  syntonin,  432 
albumin,  436 

Preparation  of  solution  of, 
433 
Acids,  Action  of,  on  blood,  29 
Adenoid  tissue,  59 
Adipose  tissue,  Chemistry  of,  447 
Albumin,  Alteration  of,  by  acids,  432 
by  alkalies,  429 
Coagulation  of,  424 
Decomposition  of,  436 
Detection  of,  426 
in  urine,  555 
Determination  of  amount  of,  in 

urine,  556 
Dry,  solubility  of,  423 
Mode  of  separating,  from  milk, 

528 
Preservation  of,  423 
Properties  of,  421 
Pure,  preparation  of,  422 
Solution  to  be  used  in  testing, 

422 
Tests  for  traces  of,  in  solution, 
428 
Albuminates,  435 
Albuminoids,  Chemistry  of,  442 
Albuminous  bodies,  Coagulated,  436 
in  solution,  437 
Precipitation  of,  424 
Separation    of,     from    otber 
substances    in     solution, 
427 
Synopsis  of,  435 
compounds,  421 

Products  of  digestion  of,  483 
substances  in  muscle,  451 
37 


Alkali  albuminates,  429,  435 

and  syntonin,  Distinction  be- 
tween, 435 
should  contain  no   sulphur, 
432 
Alkalies,  Action  of,  on  blood,  30 
Alvergniat's  pump,  205 
Amoeboid  cells,  49 
Amyloid,  436 

Analysis  of  blood  gases,  210-214 
Aniline  for  coloring  sections,  107 
Animal  heat,  336 
Apnoea,  328 
Areolar  tissue,  47 
Arterial  pressure,  218 

Changes  of,  in  each  cardiac 

period,  224 
Expansive    movements    ac- 
companying    change    of, 
220 
Influence  of,  on  frequency  of 
heart  contractions,  285 
pulse,  Experiments  with  schema 
relating  to  forms  of,  234 
schema  or  artificial  artery, 
230 
Arteries,  Observation  of,  during  ex- 
citation of  the  cord,  251 
Circulation  in,  217 
smallest,  Phenomena  of  circula- 
tion in,  238 
Artery,  Artificial,  or  arterial  schema, 

230 
Asphyxia  by   complete   occlusion   of 
the  trachea,  329 
by  slow  suffocation,  330 
State  of  circulation  in,  332 
Auerbach's  ganglia,  86 

Beale's  solution  for  coloring  sections, 

107 
Bernard's     method     of    determining 

oxygen  in  blood,  216 
Bernstein's  experiment,  282 
Bile,  I'M 


578 


INDEX. 


Bile  ocids,  199 

Separation  and  detection  of, 

in  urine,  556 
Pettenkofei's  test  for,  499 
Action  of,  604 
Composition  of,  19  I 
General  character  of,  494 
pigments;  Relation  of,  to  uromo- 
globin,  497 
Tests  for,  494 
precipitates,  syntonin  and  pepsiu, 

5!  1 1 
Secretion  of,  504 
Biliary  listula,  Mode  of  producing,  in 

guineapigs,  505 
Bilirubin,  196 

Preparation  of,  from  bile,  496 

from  gall  stones,  496 
Properties  of,  496 
Biliverdin,  497 

Properties  of,  497 
Bladder.  Epithelium  of,  42 
Blastoderm,  Formation  of  lamella:  of, 
104 
of  chick,  Lamellic  of,  165 
Blood,  175 

Action  of  acids  on,  29 
of  alkalies  on,  30 
of  boracic  acid  on,  30 
of  carbonic  acid  gas  on,  32 
of  cold  on,  188 
of  crystallized  ox-bile  on,  189 
of  electricity  on,  33,  189 
of  gases  on,  31 
of  heat  on,  188 
of  water  on,  189 
Chemical  changes  of,  in  dyspnoea 

and  asphyxia,  333 
Circulation  of,  217 
coloring  matter,  187 
Condition    affecting    coagulation 

of,  183 
corpuscle  of  mammalia,  Action  of 

.salt  solution  on,  28 
crystals,  34 

Detection  of,  in  urine,  559 
Gases  of,  204 

method  of  analysis,  210 
method    of     rendering    laky    or 

transparent,  187 
Method    of    transferring,     from 
artery  or  vein,  to  vacuum,  208 
Mode  of  testing  for  sugar  in,  509 
of  frog,  Filtration  of,  170 
Quantitative  determination  of  hae- 
moglobin in,  192 
Quantitative  analysis  of,  199 
Bloodvessels,  Endothelium  of,  118 


Bloodvessel?,  Muscular  coat  of,  120 
Nerves  of,  121 
of  intestine,  189 

Structure  of,   1  18 

Bone,  63 

Chemistry  of,  447 
Development  of,  fi  1 
Inflammation  of,  1 70 
Preparation  of  gelntigenous  sub- 
stances from,  i  1 1 
Boracic    acid.    Action    of,    on    blood, 

30 
Brain  and  spinal  cord,  Ganglion  cells 
of,  83 
Chemistry  of,  455 
Ganglion   cells   of,  hemispheres, 
85 
Branched  cells  (connective  tissue  cor- 
puscles), 51 
corpuscles  of  skin,  55 
of  tail  of  tadpole,  55 
Brunner's  glands,  138 

Calorimetry,  337 

Capillary    circulation   in    mammalia, 

240 
Carbonic  acid  gas,  Action  of,  on  blood, 
32 
Discharge  of,  by  an  ani- 
mal in  a  given  time, 
311 
Cardiac  impulse,  203 
Cardiograph,  265 

Carmine,  Coloring  of  sections  by,  106 
for  injecting,  113 
Mass,  Gerlach's,  113 
Cartilage,  hyaline,  60 
inflammation  of,  170 
Yellow,  02 
Casein,  435 

Mode  of  separating,  from  milk, 
528 
Cells,  Amoeboid,  49 
Fat,  57 
Nerve,  82 
Pigment,  56 
Tendon, 58 
Cellular  elements  of   centrum  tendi- 
neum  in  relation  to  lymphatics,  127 
Cellular,  Elements  of,  connective  tis- 
sue, 49 
Centrum  tendineum,  Cellular  elements 

of,  127 
Cerebral  hemispheres,  Removal  of,  in 

bird,  417 
Cerebrin,  450 

Cerebro-spinal  nervous  centres  of  vas- 
cular system,  influence  of,  246 


INDEX. 


579 


Changes  of  arterial  pressure  during 

each  cardiac  period,  224 
Chick,  Cleavage  cavity  of,  104 

Lamellns  of  blastoderm  of,  105 
Chloride  of  gold,  Preparation  of  cor- 
nea with,  53 
Chlorine,  Determination  of,   in  urine, 

503 
Cholesterin,  503 
Cholic  acid,  503 

Chondrin,  Decomposition  of,  447 
Chondrin,  Effect  of  boiling  on,  44G 
Precipitation  of,  446 
Preparation  of,  440 
Solubility  of,  440 
Chondrogen,  440 

Solubility  of,  440 
Chorda    tympani    and    vascular    fila- 
ments of  submaxillary  gland,  Simul- 
taneous section  of,  472 
Chorda    tympani,    Direct    and   reflex 

excitation  of,  471 
Ciliary  motion,  Effects  of  reagents  on, 
35 
Stud}-  of,  in  situ,  36 
Ciliated  cylindrical  epithelium,  35 

epithelium,  37 
Circulation,  Artificial,  242 

Capillary,  in  mammalia,  240 
in  arteries,  217 

Influence  of  respiration  on,  324 
Microscopical  study  of,  121 
Phenomena  of,  in  smallest  arte- 
ries, 238 
State  of,  in  asphyxia,  332 
Study    of,    in    cold-blooded   ani- 
mals, 121 
Study  of,  in  mesentery,  121 
in  tail  of  tadpole,  122 
in  tongue,  122 
in  web  of  frog's  foot,  121 
Cleavage    cavity  in    ova   of  fish  and 
amphibia,  101 
of  chick,  104 
process    in  ova  of   fish  and  am- 
phibia, 159 
Coagulation  of  albumin,  424 
of  blood,  183 
of  muscle  plasma,  450 
of  myosin,  452 
Cold,  Action  of,  on  blood,  188 
Cold-blooded  animals,    Study  of  cir- 
culation in,  121 
Coloring  of  sections,  106 
Colorless  blood  corpuscles,  17 
Colorless    corpuscles,   Action  of   dis- 
tilled water  on,  27 
Amoeboid  movements  of,  17 


Colorless    corpuscles,    Application    of 
liquid  reagents  to,  20 
Effects  of  warmth  on,  23 
Feeding  of,  25 
of  man,  25 
Varieties  of,  18 
Commutator,  354 
Conjunctiva  and  membrana  nictitans, 

Nerves  of,  92 
Connective  tissue,  Cellular  elements 
of,  49 
corpuscles,  51 

and  fat  cells,  Transition 
forms  between,  58 
Development  of,  59 
tissues,  46 

Chemistry  of,  442 
Constant    current,     Arrangement    of 

electrical  apparatus  for,  357 
Contraction  as  a  function  of  stimulus, 

307 
Contractions,  Idio-muscular,  305 
Cornea,  Fixed  corpuscles  of,  52 
Inflammation  of,  171 
Nerves  of,  91 
Preparation  of,  with  chloride  of 

gold,  53 
Treatment    of,    with    nitrate     of 
silver,  52 
Corpuscles,  Branched,  of  skin,  55 
of  tail  of  tadpole,  55 
Fixed,  of  cornea,  52 
Granular,  21 
Corpuscles  of  blood,  Separation    of, 
from   liquor   sanguinis,    by    subsi- 
dence, 177 
Cranial  and  spinal  nerves,  Ganglia  of, 

82 
Creatine,  453 

Decomposition  of,  453 
Reaction  of,  453 
Solubility  of,  453 
Tests  for,  453 
Creatinine,  453 

Characters  of,  454 

Reaction  of,  453 

Separation      of,      from      urine, 

538 
Solubility  of,  453 
Crystallized  bile,  500 

composition,  500 
Action  of,  on  blood,  189 
Curare,  Poisoning  by,  398 
Current,    electric,      interrupted      by 

means  of  an  oscillating  rod,  360 
Current,  electric,  with  definite  inter- 
ruptions by  means    of   the    metro- 
nome, 300 


580 


INDEX. 


Cylindrical  ciliated  epithelium,  86 
epithelium,  non-ciliated,  38 

Dammar  varnish,  Preparation  of,  108 
Death,  after  section  of  both  vagi,  317 
Development  of  bone  tissue,  G4 

of  connective  tissue,  50 
Dialysis,  505 

Diaphragm,    demonstration    of    lym- 
phatics by  injection,  126 
Diaphragm,   Lymphatics  of  centrum 

tendineum  of,  123 
Diastatic    action  of  saliva,  Effect  of 

temperature  on,  400 
Digestion,  457 

and  secretion,  421 
Effects  of  temperature  on,  486 
in  the  stomach,  475 
intestines,  515 

Method    of    making    a 

temporary  fistula,  515 

Digestion  in  the  intestines,  Method  of 

making  a  permanent  fistula,  516 
Digestion  of  the  stomach   by   itself, 
491 
during  life,  491 
Organs  of,  135 

Strength   of  acid   required   for, 
486 
Digestive  action  of  Pepsin,  483 
Discus  proligerus  and  ovum,  148 
Dorsalis  pedis,  Excitation  of,  256 
Drying,  566 
Dyspeptone,  484 
Dyspnoea,  328 

Egg  albumin,  435 
Elastic  tissue,  47 

Chemistry  of,  445 
Elastin,  445 

Characters  of,  445 
Decomposition  of,  446 
Precipitation  of,  445 
Preparation  of,  445 
Reactions  of,  445 
Solubility  of,  445 
Electric  currents  of  muscles,  376 
Natural,  376 
Negative  variations  of, 
380 
of  nerves,  381 
Natural,  381 
Negative  variations  of, 
381 
Electrical  measurement  of  tempera- 
ture, 344 
stimulation  of  nerve  and  muscle, 
364 


Electricity,  Action  of,  on  blo< 
Electrodes,  852 

Non-polarizable,  353 
Electrotonus,  382 

as  affecting  irritability,  8 
Embedding  in  gum  and  gelatine,  105 
in  wax  and  oil,  108 
of  tissues  for  cutting  sections.  1 1  '■'• 
Embryology,  158 
Endocardial  pressure,  268 

curve,   Modifications  of,  270 
in  mammalia,  27^1 
Investigation  of,  in  heart  of 

frog,  268 
Variations   of,    during  each 
cardiac  period,  269 
Endothelium  and  epithelium,  85 
Inflammation  of,  170 
of  bloodvessels,  118 
of  serous  membranes,  43 
Silver  method  of  exhibiting,  43 
Epithelial  tissues,  Chemistry  of,  442 
Epithelium  and  endothelium,  35 
of  ovary,  147 
Ciliated  forms  of,  37 
Cylindrical  ciliated,  35 

non-ciliated,  38 
Inflammation  of,  169 
of  bladder,  42 
of  kidneys,  144 
of  malpighian  corpuscles.  145 
of  villi  of  intestines,  39 
pavement,  40 
Excitation  and  section  of  spinal  cord 
in  rabbit,  248 
Direct,  of  spinal  cord  in  frog,  246 
of  dorsalis  pedis,  256 
of  nerves  of  external  ear  of  rab- 
bit, 255 
of  superior  laryngeal  nerve,  322 
of  central  end  of  one  vagus  after 

section  of  both,  321 
of  vascular   nerves    of  submax- 
illary gland,  472 
Extractive  matters  in  muscle,  452 
Evaporation,  561 

Method  of  retarding,  27 

Fallopian  tubes,  148 

Uterus  and  vagina,  148 
Fat  cells,  57 

and   connective   tissue   cor- 
puscles, Transition  forms 
between,  58 
Fats,  447 

Composition  of,  448 
Emulsionizing  of.  1 18 
Reactions  of,  4  is 


INDEX. 


581 


Fats.  Solubility  of,  447 
Feeding  of  colorless  corpuscles,  25 
Fibre  cells.  Spiral,  87 
Fibrin  and  plasma,  Properties  of,  178 
Influence  of  swelling  of,  on    its 
digestion,  487 
Fibrinogen  and  paraglobulin,  Experi- 
ments relating  to,  179 
Fibrinogenic  substance,  435 
Fibrino-plastic  substance,  435 
Fibrins,  435 
Fibro-cartilage,  62 
Fibrous  tissue,  40 

tissues,  Action  of  acetic  acid  on, 
47 
Effect  of  maceration  on,  47 
Filtration,  563 

of  frog's  blood,  176 
Fixed  corpuscles  of  the  cornea,  52 
Follicles,  Graafian,  148 

of  intestine,  Solitary  and  agnii- 

nated,  132 
of  Peyer,  138 
Frankland-Sprengel  pump,  207 
Frog,  Injection  of,  during  life,  110 
Muscular  nerve  endings  of,  98 
Piespiratory  movements  of,  298 
Study  of  movements  of  heart  in, 
260 

Ganglia,  Auerbach's,  86 

of  the  cranial  and  spinal  nerves, 82 
Ganglion   cells    of  brain    and   spinal 
cord,  83 
of  hemispheres  of  brain,  85 
of  sympathetic  system,  85 
Reproduction  of,  88 
Gases,  Action  of,  on  blood,  31 

of  arterial  blood  of  dog,  Analysis 

of,  214 
of  blood,  204 
Gastric  fistula,  Establishment  of,  475 

Operation  for,  470 
Gastric  juice,  Action  of,  479 
on  gelatine,  485 
Artificial,  479 

Effects  of  stimuli  on  secre- 
tion of,  493 
Estimation  of  acid  in,  478 
Examination  of,  477 
Secretion  of,  490 
To  determine  the  nature  of 
acid  in,  478 
Geissler's  pump,  206 
Gelatin,  444 

Action  of  gastric  juice  on,  485 
Alteration  of,  by  boiling,  445 
Precipitation  of,  1  1"j 


Gelatin,  Preparation  of,  444 

Solubility  of,  445 
Gelatigenous  substance,  444 
Characters  of,  444 
Preparation  of,  from  bone, 

444 
Preparation    of,    from    ten- 
dons, 444 
Solubility  of,  444 
Genital  organs,  147 

of  male,  149 
Gerlach's  carmine  mass,  113 
Gland,  thymus,  132 
Glands,  Lymphatic,  system,  130 
of  Brunner,  138 
Parotid,  473 

Salivary  and  pancreatic,  135 
Sebaceous,  143 
Sweat,  142 
Globulins,  435 
Glycerin,  448 

Decomposition  of,  448 
Solubility  of,  448 
Solvent  powers  of,  448 
Test  for,  449 
Glycocholic  acid,  501 
Glycogen,  506 

Conver'n  of,  into  grape  sugar,  512 
Influence  of  food  on  amount  of, 

in  liver,  512 
Preparation  of,  510 
Properties  of,  511 
Glycogenic  function  of  liver,  Mode  of 

demonstrating,  508 
Glycosuria,  513 

produced  by  puncture  of  floor  of 
fourth  ventricle,  514 
Graafian  follicles,  148 
Granular  corpuscles,  21 
Gum  or  gelatin,  Embedding  in,  105 

H?ematin,  197 
Ilrematoin,  198 
Haemin,  196 

crystals,  34 
Haemoglobin,  34 

Chemical  properties  of.  192 

Determination  of  quantity  by  es- 
timation of  its  iron,  202 

Optical  properties  of,  194 

Preparation  of,  183 

Quantitative  determination  of,  in 
blood,  201 
Hair,  144 
Hardened    tissues,     Preparations    of 

sections  from,  100 
Hearing,  Organ  of,  154 
Heart,  260 


582 


INDEX. 


Heart,  Examination  of,  after  death  by 
asphyxia,  338 

Function   of  depressor  nerve  of, 

291 
Inhibitory  nerves  of,  279 
Influence  of  temperature  on,  278 
Intrinsic  nervous  system  of,  274 
Movements  of,  260 
sounds,  Investigation  of,  266 
Study  of  movements  of,  in  frog. 
200 
in  mammalia,  262 
Heat,  Action  of,  on  blood,  l^s 

produced  by  an  animal  in  a  given 
time,  Estimation  of,  339 
Hemispheres  of  brain,  Ganglion  cells 

of,  85 
Heynsius'  experiment,  182 
Hippuric    acid,    Separation    of,    from 

urine,  537 
Hofmann's  tests  for  tyrosine,  441 
Hyaline  cartilage,  GO 
Hypoxanthine,  454 

Idio-muscular  contractions,  395 
Ignition,  560 
Impulse,  Cardiac,  263 
Inflammation  of  bone,  170 
of  cartilage,  170 
of  cornea,  171 
of  endothelium,  170 
of  epithelium,  169 
of  tongue  of  frog,  173 
Inflammatory  changes  in  liver  cells. 
171 
in  tadpole's  tail,  173 
Inflamed  tissue,  Study  of,  160 
Inhibitory  influence  of  parts  of  the 
brain  on  reflex  actions  of  the  spinal 
cord,  418 
Inhibitory  nerves  of  the  heart,  279 
Injected  tissues,  Treatment  of,  118 
Injecting  with  carmine,  113 
with  Prussian  blue,  112 
Injection  after  death,  112 

Apparatus  and  instruments  for, 

114 
of  lymphatic  glands  and  mucous 

membranes,  130 
of  the  frog  during  life,  110 
of   the   small    mammalia   during 

life,  111 
of  solution  of  nitrate  of  silver,  1 1 8 
Innervation  of  respiratory  movements, 

315 
Inosite,  455 

Inspiratory  muscles:  Diaphragm,  304 
Intercostal,  305 


Internal  absorption  by  veins  296 
Interrupted  electric  current,  359 

Intestinal  fistula.  622 
juice,  522 

Actions  of,  524 
Artificial.  528 
Intestine,  epithelium  of  villi,  39 
Large.  139 
Movements  of,  525 
Small,  137 

Solitary  and   agminated  follicles 
of,  132 
Intrathoracic  pressure,  Measurement 

of,  303 
Intrinsic  nervous  system  of  the  heart, 
274 

Kidneys,  Epithelium  of,  144 
Isolation  of  tubes  of,  145 

Kymographic  observation,  Rules  and 
precautions  in,  220 

Kymograph,  Mercurial,  219 
Spring,  225 

Lecithin,  456 
Leucine,  438 

Tests  for,  440 
Liquor  sanguinis,  175 
Liver,  139 

Absorption  by,  505 

Functions  of,  494 

Influence  of  food  on  amount  of 
glycogen  contained  in.  512 

Glycogenic  function  of,  508 

Separation  of  diastatic   ferment 
from,  513 
Lymphatic  glands,  Structure  of,  130 

system,  123 

vessels,  Stomata  of,  125 
Structure  of,  130 
Lymphatics  of  diaphragm,  126 

of  omentum  and  meseutery,  128 

Male  genital  organs,  149 
Malpighiau    corpuscles,    Epithelium 

of,  145 
Manipulation,  Practical  notes  on.  559 

of  glass  tubing,  559 
Marking  lever.  355 
Mechanical  stimulation  of  muscle  and 

nerve,  364,  395 
Medulla  oblongata,  Division  of.  406 
Excitation  of,  262-25  I 
Section  of,  within  the  cra- 
nium, 251 
Medullary  sheath  of  nerve  fibres,  80 
Meissner's   bodies  or   tactile  corpus- 
cles, 90 


INDEX. 


583 


Meissner's  plexus,  80 

Metnbrana  nictitaus  and  conjunctiva, 

Nerves  of,  92 
Mesentery,  129 

and  omentum,  Lymphatic  system 

of,  128 
Study  of  circulation  in,  121 
Metapeptone,  484 
Methaemoglobin,  190 
Microscopical    studj'    of    circulation, 

121 
Milk,  52G 

Characters  of,  526 
Constituents  of,  527 
Fats  of,  529 

Microscopical  examination  of,  52G 

Mode  of  estimating  butter  in,  529 

separating     albumin     from, 

528 
separating  casein  from,  528 
Sugar  in,  528 
Moreau's    experiment    on    intestinal 

secretion,  524 
Motion,  Ciliary  study  of,  in  situ,  30 
Mouth,  Mucous  membrane  of,  135 
Mucin,  442 
Mucous     and      serous      membranes, 

Nerves  of,  95 
Mucous  membrane  of  mouth,  tongue, 

pharynx,  and  oesophagus,  135 
Murexide  test  for  uric  acid,  435 
Muscle,  Albuminous  substance  in,  451 
and  nerve,  Mechanical    stimula- 
tion of,  395 
Aqueous  extract  of,  450 
Chemical  stimulation  of,  396 
Chemistry  of,  449 
corpuscles,  73 
curve,  365 
Exhaustion  of,  300 
Striped,  67 
Unstriped,  65 
plasma,  449 
Reaction  of,  449 
Thermal  stimulation  of,  397 
Muscles  of  respiration,  Action  of,  304 
Muscular  coat  of  bloodvessels,  120 
Muscular    contraction,    Influence    of 
temperature  on,  300 
Influence  of  veratrin,    etc., 

on,  867 
Phenomena  and  laws  of,  365 
Wave  of, 
work  done,  3G8 
Muscular  fibre,  Arrangement  and  di- 

vi-ion  of,  75 
Muscular  fibres,  P^xamination   of,  in 
polarized  light.  75 


Muscular  fibres,  Substance  of,  67 
Nerves  of,  96 

nerve  endings,  97-99 

tissue,  65 
Myosin,  435 

Nares  and  larynx,  Movements  of,  307 
Nessler's  reagent,  Preparation  of,  439 
Neurilemma,  81 
Neurin,  450 
Nerve  cells,  82 

Peripheral,  90 
chamber,  352 

Chemical  stimulation  of,  397 
endings,  89 
fibres,  79 

Axis-cj'linder,  79 
Medullary  sheath,  80 
non-medullated,  82 
Schwann's  sheath,  81 
Nerves,  Influence  of,  on  secretion  of 

stomach,  492 
Nerves  of  bloodvessels,  121 

of    conjunctiva    and    membrana 

nictitans,  92 
of  cornea,  91 
of  mucous  and  serous  membranes, 

95 
of  peritoneum,  96 
of  septum  cisternal  of  mesentery 

of  frog  and  newt,  95 
of  skin,  93 
of  striped  muscle,  97 
of  tadpole's  tail,  94 
of  unstriped  muscular  fibre,  96 
Stimulation  of,  385 
Thermal  stimulation  of,  398 
Vasomotor  functions  of,  244 
Nervous  system,  Tissues  of,  79 

Omentum  and  mesentery,  Lymphatics 

of,  128 
Optic  lobes,  Irritation  of,  418 
Organs  of  digestion,  135 
of  respiration,  133 
of  special  sense,  150 
Ova  of  fish  and  amphibia,  Process  of 

cleavage  in,  159 
Ovary,  Epithelium    and  endothelium 
of,  147 
stroma  of,  148 
Ovum  and  discus  proligerus,  148 

Pancreas  and  salivary  glands,  135 
Pancreatie   ferments,  Glycerin   solu- 
tion of,  518 
Pancreatic  ferments,  Isolation  of,  520 
juice,  515-521 


;84 


INDEX. 


Pnraglobulin  and  fibrinogen,  Experi- 
ments relating  to,  179 
Parapeptone,  488 

Parotid  duct,  Insertion  of  cauula  in, 
405 
fistula,  4G6 

glands,  473 

Peritoneum,  Nerves  of,  96 

Peyer's  follicles,  138 

Phosphoric   acid,    Estimation    of,   in 
urine,  551 

Picric  acid,  Coloring  of  sections  by, 
107 

Pigment  cells,  56 

Piria's  test  for  tyrosine,  441 

Plasma,  or  liquor  sanguinis,  175 

Polariscope,  571 

Polarized  light,  Examination  of  mus- 
cular fibres  in,  75 

Precipitates,  Washing  of,  on  niters,  205 

Precipitation,  562 

Pressure,  Arterial,  218 
Endocardial,  208 
produced  by  secretion,  471 

Prussian  blue  for  injecting,  112 

Pseudo-stomata,  12s 

Ptyalin,  402-3 

Pulse,  Arterial,  experiments  relating 
to  forms  of,  234 

Pumps,  Alvergniat's,  Geissler's,  and 
Franklaud-Sprengel,  207 

Recording  tuning-fork,  357 
Recurrent  sensibility,  405 
Keflex  actions,  400 

excitation  of  medulla  oblongata, 
252-254 
of  vagus,  283 
of  vaso-motor  centres,  252 
Respiration,  208 

Influence  of,  on  circulation,  324 
Organs  of,  133 
Respiratory  movements,  Innervation 
of,  315 
of  frog,  298 
Roots  of  spinal  nerves,  Functions  of, 
402 

Saliva  and  its  secretion,  457 
Action  of,  459-462 
Artificial,  402 
Effect   of  temperature   on  dias- 

tatic  action  of,  400 
Inorganic  constituents  of,  458 
Organic,  469 
Secretion  of,  after  decapitation, 

475 
Separation  of  ptyalin  from,  403 


Salivary  fist  nice,  166 

glands  and  pancreas,  185 

Preparation  of  mucin  from, 

1 18 
Secretion  of,  in  rabbit,  465 
secretion,  Stimulation  of,  16  I 
Sarcolemma,  72 
Sarcous  elements,  449 
Sarkin,  454 
Scherer's  test  for  leucine,  1  10 

tyrosine,  441 
Schwann's  sheath,  81 
Sebaceous  glands,  143 
Secretion  of  gastric  juice,  400 
of  saliva,  464 

of  stomach,  Influence  of  nerves 
on,  492 
Section  of  both  vagi  in  the  neck,  815 
of  medulla  oblongata  within  the 
cranium,  251 
Sections,  Coloring  of,  100 
Mounting  of,  107 
of  fresh   tissues,  Preparation  of, 

1(H) 
of  hardened  tissues,  Preparation 
of,  100 
Semicircular  canals,  Division  of,  420 
Sensibility,  Recurrent,  405 
Serous  membranes,  43 
Serum  albumin,  423 
Skin,  141 

Branched  corpuscles  of,  55 
Nerves  of,  93 
Sight,  Organ  of,  150 
,  Silver,  Solution  for  injecting,  114,  118 
Smell,  Organ  of,  157 
Sounds  of  the  heart,  200 
Special  sense,  Organs  of,  150 
Specific  gravity,  567 
Sphvgmograph,  227 

"Uses  of,  229 
Spinal  and  cranial  nerves,  Ganglia  of, 
82. 
cord,  Excitation  of,  240,  248. 
Spiral  fibre  cells,  87 
Splanchnic  nerves,  Vaso-motor  func- 
tions of,  258 
Spleen,  140 

Spring  kymograph,  225 
Starch  paste,  Action  of  saliva  on.  459 
Stimulation    of  muscles   and   nerves, 

304,  385. 
Stomach,  130 

Digestion  of,  during  life,  491 
Strieker's  warm  stage,"  22 
Striped  muscle,  67 

Nerves  of,  97 
Stroma  of  ovary,  148 


INDEX. 


585 


Submaxillary  fistula,  4G6 

ganglion,  Functions  of,  473 
gland,  Excitation   of  vaso-motor 
nerves  of,  471 
Investigation  of  functions  of, 
467 
Sugar,  Detection  of,  in  urine,  553 

Testing  for,  in  blood,  509 
Sweat  glands,  142 

Sympathetic  system,  Ganglia  of,  85,86 
nerve,   Vaso-motor   functions   of 
cervical  portion  of,  257 
Syntonin,  or  acid  albumin,  432 

Tactile  corpuscles,  90 
Tannin,  Action  of,  on  blood,  31 
Taste,  Organ  of,  155 
Taurocholic  acid,  502 
Taurine,  502 
Teeth,  135 

Temperature,  Distribution  of,  in  body, 
348 

Electrical  measurement  of,  344 
Tendons,  Preparation  of  gelatigenous 
substance  from,  444 
of  mucin  from,  443 
Tetanus,  371 

Curve  of,  371 

effects  of  exhaustion,  372 
Thermal  stimulation  of  muscle   and 

nerve,  364,  397-8 
Thermometry,  343 
Thymus  gland,  132 
Tissues,  Chemistry  of,  442 

Process  of  teasing,  46 
Tongue,  Mucous  membrane  of,  135 

of  frog,  Inflammation  of,  173 

Study  of  circulation  in,  122 
Traube's  curves,  326 
Tuning-fork,  857 
Tyrosine,  440 

Preparation    of,    by    pancreatic 
digestion,  521 

Tests  for,  441 

Unstriped  muscle,  65 

Nerves  of,  96 
Urari,  Poisoning  by  (see  also  Curare), 

Urea,  Determination  of,  in  urine,  547 

1'reparation  of,  from  urine,  534 
Ureter,  pelvis  of  kidney,  and  bladder, 

147 
Uric  acid,  466 

Determination  of,  in  urine, 
661 
Urinary  apparatus,  144 
deposits,  683 
38 


Urine,  531 

Detection  of  blood  in,  557 
Constituents  of,  534 
Determination    of    albumin    in, 
556 
of  chlorine  in,  549 
of  phosphoric  acid  in,  551 
of  sugar  in,  553 
of  sulphuric  acid  in,  552 
of  urea  in,  547 
quantity  passed  in  a  given  time, 

541 
Reactions  of,  531,  533 
Separation   of  bile    acids   from, 
556 
of    coloring   matters    from, 

539 
of  creatinine  from,  538 
of  hippuric  acid  from,   537 
Specific  gravity  of,  542 
Uterus,  Fallopian  tubes,  and  vagina, 
148 

Vagus  and  splanchnic  nerves,  Influ- 
ence of,  on  stomach,  493 
nerve,   Influence    of,    on   heart, 

279-80 
Reflex  excitation  of,  283 
Valves,  Study  of,  in  dead  heart,  267 
Varnished    rabbits,    Increased     dis- 
charge of  heat  from,  342 
Vascular  system,  Methods  of  inject- 
ing, 110 
Vasomotor,    Centre  reflex  excitation 
of,  252 
functions   of  splanchnic  nerves, 
258 
of  cervical   portion    of   the 
sympathetic,  257 
nerves,    Excitation  and   division 
of,  250 
Functions  of,  244 
Veins  and  lymphatics,  Absorption  by, 
293 
Internal  absorption  by,  296 
Villi  of  intestine,  Epithelium  of,  39 
Vitellin,  435 
Volumetrical  analysis,  569 

Warm  stage,  22 

Wax  and  oil,  Embedding  in,  103 

Web   of  frog's  foot,    Circulation   in, 

121 
Weighing,  567 

Xanthine,  454 

Yellow  cartilage,  62 


LIST  OF  ILLUSTRATIONS 


PLATE  I. 

Fig.    1.  Simple  Arrangement  for  warming  an  Object  under  the  Microscope. 
"     12.   Similar  but  more  complicated  Apparatus. 
"       2.   Strieker's  Warm  Stage. 
"     13.  Rod  for  Heating  Stage. 
"     16.  Object  Support  with  Gas  Chamber. 

PLATE  II. 

Fig.    3.  Mode  of  warming  an  Object  under  the  microscope  by  means  of  Current 
of  Hot  Water. 
"       4.  Capillary  Pipette. 
"     14.   Strieker's  Stage  for  warming  a  Preparation  by  Voltaic  Current. 

PLATE  III. 

Fig.     5.   Carbonic  Acid  Apparatus. 
"       6.  Microscope  Stage  with  Strieker's  Electrodes. 

PLATE  IV. 

Fig.  17.  Injecting  Syringe. 
"     11.   Support  for  Study  of  Circulation  in  Web  of  Frog's  Foot. 
"     20.  Injecting  Canuloo. 
"     21.   Section  Knife. 
"     18.  Nozzle  of  Injection  Syringe. 
"     19.  Support  for  Studying  Circulation  in  Mesentery. 

PLATE  V. 

Fig.  22.  Large  Colorless  Corpuscle  of  Newt. 
"     23.   Granular  Corpuscle  of  Newt. 
"     24.  Action  of  different  Reagents  on  Blood  Corpuscles. 

PLATE  VI. 

Fig.  2(5.  Action  of  Heat  on  Colorless  Corpuscles  of  Human  Blood. 
"       7.  Epithelial  Cells  from  Trachea  of  Cat. 

PLATE  VII. 

Fig.  2G.  Epithelial  Cells  from  Bladder  of  Rabbit. 
"     27.  "     of  Bete  Malpighii  from  Pointed  Condyloma. 

"     28.  Superficial  Cells  of  the  same  Preparation. 

"     2'J.  Jagged  Epithelial  Cells  of  Gum. 

PLATE  VIII. 

Figs.  30  and  32.  Abdominal  Surface  of  Centrum  Tendineum  of  Rabbit. 
Fig.    31.  Pleural 

PLATE  IX. 

Fig.  33.  Omentum  of  Guineapig  treated  with  Silver. 
"     34.  Fenestrated  Portion  of  Omentum  of  Ape. 


IV  LIST    OF    ILLUSTRATIONS. 


PLATE  X. 

Pig.  35.  Omentum  of  Ape,  showing  Group-;  of  germinating  Endothelial  •'■■ll--. 
"     37.  Silver  Preparation  of  Septum  of  Cisterna  Lymphaticn  of  Female  Frogs. 

FLATE  XI. 

Fig.  37.  Germinating  Endothelium  of  Pleural  Mediastinum  of  Cnt. 

"     38.  Mesogastrium  of  Frog  covered  with  Ciliated  germinating  Endothelium. 

PLATE  XII. 

Fig.  39.  Cornea  of  Frog  treated  with  Lunar  Caustic. 
"     40.  Horizontal  Preparation  of  Cornea  of  Frog  colored  with  Chloride  of  Gold. 

PLATE  XIII. 

Fig.  41.   Horizontal  Preparation  of  Cornea  of  Rabbit  treated  with  Lunar  Caustic 
and  Salt  Solution. 
"     42.  Membrana  Nietitans  of  Frog  treated  with  the  Chloride  of  Gold. 
"     43.   Surface  of  Inflamed  Mesentery  of  Ape. 

"     44.         "  "  "  "         showing  Branched  Cells  of  Ca- 

nalicular System  filled  with  Fat  Globules. 
"     45.  Fat  Cells,  Omentum  of  Rat. 

PLATE  XIV. 
Figs.  46  and  47.  Cells  of  Gelatinous  Substance  of  Infra-orbital  Fossa  of  Rabbit. 

PLATE  XV. 

Fig.  48.   Cells  of  Parietal  Peritoneum  of  R'abbit  with  Chronic  Peritonitis. 
"     49.       "     of  Submucous  Tissue  of  Gravid  Uterus  of  Sow. 
"     50.       "     of  Gelatinous  Substance  of  Infra-orbital  Fossa  of  Rabbit  being 
converted  into  Fat-cells. 

PLATE  XVI. 
Fig.  51.  Branched  Cells  of  Omentum  of  Rabbit. 

PLATE  XVII. 
Fig.  52.  Cells  of  Caudal  Tendon  of  young  Rat ;   Silver  Preparation. 
"     53.       "  "  "         of  full-grown  Rat. 

"     54.       "  "         of  young  Rut ;   Gold  Preparation. 

"     55.  Transverse  Section  of  Tendon  from  Tail  of  Rabbit. 
"       8.  Connective  Tissue  Trabeculaj  from  Omentum  of  Guineapig. 

PLATE  XVIII. 

Fig.  5G.  Elastic  Fibres  from  Mesentery  of  Rabbit. 
"     57.  Intervertebral  Cartilage  of  Tail  of  Rabbit. 

PLATE  XIX. 
Fig.  58.  Transverse  Section  of  Epiphysis  of  Femur  of  Human  Foetus. 

PLATE  XX. 
Fig.  59.  Longitudinal  Section  of  Epiphysis  of  Femur  of  Human  Foetus. 

PLATE  XXI. 

Fig.  GO.  Transverse  Section  of  Diaphyaifl  of  Femur  of  Human  Foetus. 


LIST    OF   ILLUSTRATIONS.  V 

PLATE  XXII. 
Fig.  61.  Vertical  Section  of  Parietal  Bone  of  a  Child. 

PLATE  XXIII. 

Fig.  62.  Longitudinal  Section  of  Epiphysis  of  Metatarsal  Bone  of  Rabbit. 
PLATE  XXIV. 

Fig.  15.  Diagram  to  illustrate  the  Course  of  a  Ray  of  Light  transmitted  through 
a  Muscular  Fibre. 
"     63.  Longitudinal  section  of  Muscular  Coat  of  Fallopian  Tube  of  Sow. 
"     64.   Transition  of  Striped  Muscular  Fibre  into  Tendon  in  Tail  of  Rabbit. 
"     65.   Muscular  Fibre  of  Hydrophilus  Piceus. 

PLATE  XXV. 

Fig.  66.  Section  of  Injected  Muscle. 
"     67.   Smooth  Muscular  Fibre. 
"     68.   Striped  Muscular  Fibre  of  Frog. 

PLATE  XXVI. 

Fig.  69.  Group  of  Ganglion  Cells  of  a  Sympathetic  Nerve  Trunk  from  Bladder  of 
Rabbit. 
"     70.   Ganglion  Cells  with  Spiral  Fibres. 

PLATE  XXVII. 

Fig.  71.   Ganglion  Cells  from  Spinal  Cord  of  Calf. 
"     73.   Superficial  Intra-epithelial  Network  of  Non-medullated  Nerve  Fibres 

from  Cornea  of  Rabbit. 
"     74.  Sub-epithelial  Nerve-plexus  from  Cornea  of  Rabbit. 

PLATE  XXVIII. 

Fig.  72.   Branched  Ganglion  Cell  from  Spinal  Cord  of  Calf. 
11     75.  Nerves  of  Substantia  Propria  of  Cornea  of  Rabbit. 

PLATE  XXIX. 

Fig.  76.   Intra-epithelial  Non-medullated  Nerve  Fibrils  of  Cornea  of  Rabbit. 
"     77.  Auerbaclrs  Plexus  from  small  Intestine  of  Human  Foetus. 

PLATE  XXX. 

Fig.  78.  Sub-epithelial  Nerve  Branchings  of  Cornea  of  Guineapig. 
"     79.  Non-medullated  Nerve  Fibres  from  Cornea  of  Rabbit. 

PLATE  XXXI. 

Fig.  80.   Superficial  Intra-epithelial  Network  of  Non-medullated  Nerve  Fibres, 
Cornea  of  Guineapig. 
"     81.  Non-medullated  Nerve  Fibres  from  Cornea  of  Frog. 

PLATE  XXXII. 

Fig.  82.  Nerve  Fibres  of  Substantia  Propria  of  Cornea  of  Frog. 
"     83.   Bab-epithelial  and  deep  Intra-epithelial  Nerve  Fibrils  from  Cornea  of 
Babbit. 

PLATE  XXXIII. 

Fig.  84.  Deep  Intra-epithelial  Network  of  fine  Non-medullated  Nerve  Fibres  of 
Cornea  of  Babbit. 
"     85    Superficial  [ntra-epithelial  Nerve  Fibres  of  Cornea  of  Rabbit. 
"    86.  Nerve  Fibre*  and  Corpuscles  of  Cornea  of  Frog. 


VI  LIST    OF    [LLUSTRAT1 


PLATE  XXXIV. 

Fig   87.  Non-medullated  Nerve  Fibres  of  a  Capillary  Bloodvessel. 

"     8S.   Nerve  Fibres  of  Mesentery  of  Frog. 

PLATE  XXXV. 
Fig.  89.  Nerve  Fibres  and  Capillary  Bloodvessel  from  Tail  of  Tadpole. 

PLATE  XXXVI. 

Fig.  90.   Plexus  (if  Non-medullated  Nerve  Fibres  round  Capillary  Bloodvessel  from 

Mesentery  of  Frog. 
"     91.   Non-medullated  Nerve  Fibres  surrounding  Capillary  Bloodvessel  from 

Tongue  of  Frog. 
"     92.  Plexuses  of  Non-medullated  Nerve  Fibres  surrounding  Bundles  of  Un- 

striped  Muscle  from  Vagina  of  Babbit. 

PLATE  XXXVII. 

Fig.  93.   Distribution  of  Non-medullated  Nerve  Fibres  from  Base  of  a  Gland  of 
Membrana  Nictitans  of  Frog. 
"       9.  Non-medullated  Nerve  Fibres  surrounding  small  Artery  of  Tongue  of 
Frog. 

PLATE  XXXVIII. 

Fig.  94.   Sub-epithelial  Non-medullated  Nerve  Fibres  of  Vagina  of  Rabbit. 

"  95.  Non-medullated  Nerve  Fibres  in  Adventitia  of  large  Vein  from  Mesen- 
tery of  Frog. 

•'  96.  Non-medullated  Nerve  Fibres  in  Adventitia  of  large  Artery  from  Mesen- 
tery of  Frog. 

PLATE  XXXIX. 

Fig.  97.  Sub-epithelial  Non-medullated  Nerve  Fibres  of  Membrana  Nictitans  of 
Frog. 
"    98.   Bloodvessels  of  Injected  Mesenteric  Gland  of  Guineapig. 

PLATE  XL. 

Fig.  99.  Longitudinal  Section  of  Branch  of  Pulmonary  Artery  from    Lung  of 
Guineapig. 
"   100.  Transverse  Section  of  Artery  from  Skin  of  Guineapig;  Gold  Preparation. 
"   101.  Omentum  of  Rabbit,  showing  Development  of  young  Capillaries. 
"   102.  Capillary  Bloodvessel  extending  into  a  Branched  Cell. 

PLATE   XLI. 

Fig.  103.  Endothelium  of  a  large  Vein  and  Artery  of  Omentum  of  Rabbit ;  Silver 
Preparation. 

PLATE  XLII. 

Fig.  104.  Endothelium  of  Capillary  Bloodvessel  of  Omentum  of  Rabbit. 

PLATE  XLIII. 

Fig.  105.   Capillary  System  of  Mucosa  from  Injected  Stomach  of  Rat. 
"    106.  Fat  Tract  from  Injected  Omentum  of  Goineopig. 

"  107.  Superficial  Capillary  Meshworkof  Mucous  Membrane,  Injected  Uterus 
of  Guineapig. 

PLATE  XLIV. 

Fig.  108.   Superficial  Arteries,  dense  Network  of  Capillaries,  and  deep  Veins  of 
Mucous  Membrane  of  Stomach  of  Rat. 
"    109.  Masses  of  Tubercle  from  Injected  Omentum  of  Guineapig. 


LIST    OF    ILLUSTRATIONS.  Vll 

PLATE  XLV. 
Fig.  110.   Bloodvessels  of  Striped  Muscle  from  Injected  Tongue  of  Rabbit. 

PLATE  XLVI. 

Fig.  111.   Stomata  of  Mesentery  of  Frog. 
"     112.   Stomata  of  Septum  Cisternal  Lymphaticse  Magna;  of  Frog. 

PLATE  XLVII. 

Fig.  113.   Germination  of  Endothelium  round  Stomata  of  Mesentery  of  Guinea- 
pig  affected  with  Chronic  Inflammation. 

PLATE  XLVIII. 

Fig.  114.   Stomata  of  Peritoneal  Surface  of  Centrum  Tendineum  of  Rabbit. 
••     115.  Stomata  on  a  Lymph  Vessel  of  Mesentery  of  Guineapig. 

PLATE  XLIX. 

Fig.  116.   Germination  of  Endothelium  on  Mesentery  of  Guineapig  affected  with 
Chronic  Inflammation  ;   Silver  Preparation. 

PLATE  L. 

Fig.  117.  Lymph   Capillaries   of  Peritoneal  Serosa   of  Centrum    Tendineum   of 
Rabbit. 
"    118.  Lymph  Vessels  of  Pleural  Serosa  of  Centrum  Tendineum  of  Guinea- 
pig- 

PLATE  LI. 

Fig.  119.   Pleural  Surface  of  Centrum  Tendineum  of  Rabbit,  showing  rich  Net- 
work of  Lymph  Vessels. 

PLATE  LII. 
Fig.  120.  Lymphatics  of  Centrum  Tendineum  of  Rabbit. 

PLATE  MIL 

Fig.  121.  Lymphatics  of  Omentum  of  Rabbit;  Silver  Preparation. 

PLATE  LIV. 

Fig.  122.  Surface  of  Omentum  of  Rabbit,  showing  Distribution  of  Lymph  Ves- 
sels j   Silver  Preparation. 

PLATE  LV. 

Fig.  123.  Pleural  Side  of  Centrum  Tendineum  of  Guineapig  affected  with  Chronic 
Inflammation. 

PLATE  LVI. 
Fig.  124.   Pleural  Side  of  Centrum  Tendineum  of  Rabbit;  Silver  Preparation. 

PLATE  LVII. 

Fig.  125.  Lymph  Vessels  of  Pleural  Side  of  Centrum  Tendineum  of  Rabbit. 

PLATE  LVII  I. 

Fig.  120.  Artery  and  Lymphatic  Vessel  of  Omentum  of  Rabbit ;  Silver  Prepara- 
t  [on. 
"     127.   Adenoid  Tissue  of  Mesenteric  Gland  of  Ox. 


Y1U  LIST    OF    ILLUSTRATIONS. 

PLATE  LIX. 
Fig.  12S.  Natural  Injection  of  Lymphatics  of  Centrum  Tendineuni  of  Rabbit. 

PLATE  LX. 
Fig.  129.   Section  of  Medullary  Substance  of  Mesenteric  Gland  of  Ox. 

PLATE  LXI. 

Fig.  ISO.  Alveolus  from  Section  of  Lung  of  Rabbit. 
'•     132    Section  of  Lung  of  Rabbit  Injected. 
"     133.  Trabecule  of  Liver  Cells  of  Guineapig. 

PLATE  LXII. 

Fig.  134.   Section  of  Liver  of  Dog  Injected  from  Vena  Porta). 
"     130.    Section  of  Liver  of  Rabbit,  the  Portal  Vein  and  Hepatic  Duct  of  which 
are  Injected. 

PLATE  LXIII. 

Fi£.  130.  Section  of  Injected  small  Intestine  of  Rat. 

"     137.  "       "     Villus  of  small  Intestine  of  Cat. 

"     138.  "       "     Filiform  Papilla)  of  Tongue  of  Rabbit. 

"     139.  "       "     Large  Bronchus  of  Human  Foetus. 

PLATE  LXIV. 

Fig.  140.   Injected  Follicles  of  Section  of  Peyer's  Patches  from  small  Intestine 
of  Rabbit. 
"    141.   Section  of  Ileum  of  Dog. 

PLATE  LXV. 

Fig.  142.   Section  of  Acinus  from  Liver  of  Rabbit. 
"     143.   Section  of  Injected  Kidney  of  Rat. 
"    144.   Urinary  Tubes  of  Pyramidal  Substance  of  Injected  Kidney  of  Pig. 

PLATE  LXVI. 

Fig.  145.  Transverse  Section  of  Injeoted  Kidney  of  Rat. 

PLATE   LXVII. 

Fig    14fi.   Transverse  Section  of  Pyramidal  Substance  of  Kidney  of  Pig. 
'•     147.   Preparation  from  Kidney  of  Pig  showing  a  llenle's  Loop. 
"     148.   Similar  Preparation,  showing  Portion  of  Collecting  Tube  in  Pyramidal 

Process. 
"    149.  Section  of  Malpighian  Corpuscles  of  Kidney  of  Human  Foetus. 

PLATE  LXVIII. 

Fig.  150.   Convoluted  Tube  of  Kidney  of  Pig. 
"     151.   Section  of  Eyelash  of  newly-born  Child. 
,;    152.   Meibomian  Follicle  from  Section  of  Human  Eyelid. 

PLATE  LXIX. 

Fig.  153.  Tubular  Glands  of  Human  Prostate. 
"    154.   Section  of  Cortical  Substance  of  Kidney  of  Six  Months' Human  Fcetus. 
"    155.  Tubular  Glands  of  Human  Eyelid;   Vertical  Section. 

PLATE  LXX. 

Fig.  156.  Cornea  of  Rabbit  j  Vertical  Section. 
"     157.   Diagram  of  Connective  Substance  of  Retina. 
"    158.  "  Nervous  Elements  of  Retina. 


LIST    OP   ILLUSTRATIONS.  IX 


PLATE  LXXI. 


Figs.  159-163.   Blastoderm  of  Egg  of  Trout,  Various  Stages  of  Cleavage  in. 
'•     164.   Germ  of  Egg  of  Trout  in  an  early  Stage  of  Cleavage. 
"     165.   Blastoderm  of  Egg  of  Trout  at  the  Third  Day;  Vertical  Section. 
"     166.   Similar  Preparation  at  the  Sixth  Day. 

PLATE  LXXII. 

Fig.  167.   Blastoderm  of  Egg  of  Trout,  Twelfth  Day  ;  Vertical  Section. 
"     169-172.  Sections  of  Egg  of  Bufo  Cinerus. 

PLATE  LXXIII. 

Fig.  168.  Blastoderm  of  Trout's  Egg  at  Fourteenth  Day. 
"     173.   Section  through  Rudiment  of  Emhryo  of  Bufo  Cinereus. 

PLATE  LXXIV. 

Fig.  174.  Section  showing  the  Four  Embryonal  Coats  of  Rusconi's  Cavity. 

"    175.  Blastoderm  of  Fresh-laid  Hen's  Egg. 

"    176.  Blastoderm  of  Hen's  Egg  at  Fifteenth  Hour  of  Incubation. 

"    177.  Section  of  Rudiment  of  Embryo  at  Twenty-sixth  Hour  after  Incubation. 

PLATE  LXXV. 

Fig.  178.   Section  of  Rudiment  of  Embryo  at  Thirty-sixth  Hour. 
•■     179.  "  Area  Opaca  and  Area  Pellucida  at  Thirtieth  Hour. 

"     180.  Embryo  of  Chick  at  Thirtieth  Hour  ;   Section  of  Cervical  Portion. 

PLATE  LXXVI. 

Fig.  181.  Embryo  of  Chick,  Second  Day,  showing  Development  of  the  Heart. 
"     187.  Development  of  Blood  in  Blastoderm  of  Chick. 

PLATE  LXXVII. 

Fig.  1S2.   Embryo  of  Chick  at  Forty-eighth  Hour;   Section  of  Posterior  Part  of 
Body. 
"     183.   Section  of  Anterior  Cerebral  Vesicle  and  Primary  Optic  Vesicle. 

PLATE  LXXVIII. 

Figs.  184-1S6.   Transformation  of  Primary  into  Secondary  Optic  Vesicle  and  De- 
velopment of  Crystalline  Lens. 
"     188.   Development  of  Blood  in  Chick. 

PLATE  LXXIX. 

Fig.  190.  Test  Tube  with  Foot. 
"     191.  Vessel  for  collecting  Blood  and  keeping  it  at  0°  C. 
'•     192.  Coagulation  of  Blood  of  Frog  in  a  tine  Capillary  Tube. 
'     193.   Canula  for  Schiifers'  Experiment. 
"     194.  Object  Glass  for  Studying  Action  of  Induction  Shocks  on  Blood. 

PLATE  LXXX. 

1  fig.   195.  Absorption  Spectra. 

196.  Hoppe-SeyJer's  Bottle  for  Preparing  Fibrin. 

"      197.  Alvergniat's  Pump. 

"      198.  Geissler'fl  Mercurial  Pump. 

PLATE  LXXXI. 

Pig,  199.    Frankland-Sprengel  Pump. 
••     203.    Needles  for  posting  Ligatures  under  Vessels  ;   BrUcke's  Blunt  Hook; 
and  Trephine. 


X  l.I-T    OF    ILLUSTRATIONS. 

PLATE  LXXXII. 
Fig.  200.  Frankland's  Apparatus  for  Analysis  of  Gases  by  Absorption. 

PLATE  LXXXIII. 

Fig.  204.  Czermak's  Rabbit  Sui>port. 
"     201.  Frankland  and  Ward's  Apparatus  for  Analysis  of  Gases  by  Explosion. 

PLATE  LXXXIV. 

Fig.  202.   Mercurial  Kymograph. 
"     206.  Normal  Tracing  obtained  with  Mercurial  Kymograph. 

PLATE  LXXXV. 

Fig.  205.   Fick's  Spring  Kymograph. 
"     207.   Normal  Tracing  obtained  with  Spring  Kymograph. 
"     207a.  Tracing  obtained  after  Excitation  of  Vagus. 
"     208.   Mechanical  Arrangement  of  Sphygmograph. 

PLATE  LXXXVL 

Fig.  200.  End  View  of  Block  by  which  Sphygmograph  rests  on  the  Wrist. 
"     209A.   Breguet's  Improvement. 
"     210.    Mode  of  Measuring  Pressure. 
"     211.   Arterial  Schema. 

PLATE  LXXXVII. 

Fig.  212.   Tracing  obtained  with  Arterial  Schema. 
"     213.   Percussion  Waves. 

"     21-1.  Tracings  showing  the  Contractions  and  Expansions  of  an  India-rubber 
Tube,  along  which  Water  is  propelled  in  an  Intermitting  Stream. 
"     215.   Sphygmographic  Tracings. 
"     216.  Dr.  Caton's  Fish  Trough. 

PLATE  LXXXVIII. 

Fig.  217.  Stage  for  Mesentery  of  Frog. 

"     218.  Canules  for  Aorta  and  Vena  Cava  of  Frog. 

"     219.  Diagram  of  Arrangement  for  Measuring  Objects  under  Microscope. 

il     220.  Canula  for  Injecting  Liquid  into  a  Vein. 

"     221.  Griffin's  Blower  and  Expanding  Regulator. 

PLATE  LXXXIX. 

Fig.  222.   Sprengel's  Blower. 
"     223.   Mercurial  Breaker  for  Artificial  Respiration. 
"     224.   Skull  of  Rabbit  seen  from  behind. 
"     225.  Excitor. 

"     226.   Parts  exposed  in  Rabbit  by  an  Incision  from  Thyroid  Cartilage  to 
Root  of  Left  Ear. 

PLATE  XC. 

Fig.  227.  Carotid  Artery  of  Rabbit  and  Parts  in  relation  with  it. 

"     228.  Heart  of  Frog. 

"     230.  Cardiograph. 

"     231.  Marey:s  Tympanum  and  Lever. 

PLATE  XCI. 
Fig.  233.  Coats1  Apparatus. 


LIST    OF    ILLUSTRATIONS.  XI 


PLATE  XCII. 

Fig.  235.   Tracings  recording  simultaneously  Variations  of  Pressure  in    Right 
Auricle,  Right  Ventricle,  and  Left  Ventricle. 
"     236.  Septum  Auricularum  of  Frog. 
"     237.  Dissection  of  Vagus  Nerve  of  Frog,  right  side. 

PLATE  XCIII. 

Fig.  240.  Sketch  illustrating  Relations  of  Ganglionic  Cord  in  Visceral  Cavity  of 
Frog. 
"     241.  Heart,  Lungs,  and  great  Vessels  of  Rabbit. 
"     242.  Dissection  of  lower  Cervical  Ganglion  of  Dog. 

PLATE  XCIV. 

Fig.  243.  Inferior  Cervical  Ganglion  of  Rabbit. 
"     244.  Tracing  showing  Effect  of  Electrical  Stimulation  of  Vagus  of  Frog 

under  the  Influence  of  Nicotin. 
"     246.  Respiratory  Muscles  of  Frog. 
"     247.  Recording  Stethometer. 

PLATE  XCV. 

Fig.  250.   Pulley  for  recording  Movements  of  Needle  inserted  in  the  Diaphragm. 
"     251.  Rosenthal's  Apparatus  with  W.  Mailer's  Valves. 
"     252.  Pettenkofers  Tube  for  Absorption  of  Carbonic  Acid  Gas. 

PLATE  XCVI. 

Fig.  257.  Lever  Kymograph. 
"     258.  Tracing  obtained  with  Lever  Kymograph. 

PLATE  XCVII. 

Fig.  265.  Calorimeter. 
"       "      Galvanometer. 

•'       "      Wooden  Frame  on  which  Galvanometer  Wire  is  coiled. 
"      "      Magnets  of  Galvanometer. 

PLATE  XCVIII. 

Fig.  229.  Tracing  drawn  by  Lever  applied  to  Apex  of  Heart  of  Frog. 

"  232a.  "  obtained  with  Cardiograph  applied  to  Seat  of  Impulse  of  Hu- 
man Heart. 

"  2325.  "  obtained  with  Cardiograph  applied  outside  Seat  of  Impulse  of 
Human  Heart. 

"     234.         "       of  Endocardial  Pressure  of  Heart  of  Frog. 

"  238a  &  b.  Tracings  of  Arterial  Pressure  and  Respiratory  Movement  of  Air 
in  Trachea  before  and  after  Section  of  both  Vagi. 

"  239a  <fc  b.  Tracing  of  Arterial  Pressure  of  Rabbit  during  Excitation  of  Peri- 
pheral End  of  Divided  Vagus. 

"  245.  Tracing  of  Arterial  Pressure  during  Excitation  of  Central  End  of  De- 
pressor Nerve. 

PLATE  XCIX. 

Fig.  246&*.  Tracing  of  Respiration  of  Frog. 
••'    248.  "         obtained  with  the  Stethometer. 

"     219.  ''         of  Intrathoracic  Pressure. 

"     253.   Tracings  of  Respiration  of  Cat,  before  and  after  Section  of  both  Vagi. 
"     263a.  Tracing  of  Arterial  Pressure  and  Respiratory  Movements  in  Second 

Stage  of  Asphyxia  by  Occlusion. 
"     2634.  Slow  Asphyxia. 


XI]  LIST    OF    II.U  STRATIONS. 


PLATE  C. 


Figs.  259-61.  Tracings  of  Respiratory  M"vements  of  Dog,  before  ami  after 
Curarization. 

"  262.  Tracings  of  Artificial  Respiration  and  Arterial  Pressure,  showing 
Traube's  Curves  with  Vagi  intact. 

"  264.  Effect  of  Single  Injection  of  Air  in  a  Curarized  Dog  after  Discontinu- 
ance of  Artificial  ltespiration. 

PLATE  CI. 

Figs.  254-55.   Excitation  of  Central  End  of  Vagus  in  the  Rabbit. 
"    256.  Excitation  of  Central  End  of  Superior  Laryngeal  Nerve. 

PLATE  OIL 

Fig.  266.  Diagram  of  Frog,  showing  Lines  of  Incision  necessary  in  various  Ob- 
servations. 
"     267    Diagram  of  Muscles  of  Leg  of  Frog. 
"     268.  Nerve-Muscle  Preparation. 

PLATE  Cm. 

Fig.  269.  Myographion  of  Pfliiger. 
"     270.  Moist  Chamber,  with  Nerve-muscle  Preparation. 
"     270£/j.   Simple  Spring  Myograph  of  Marey. 

PLATE  CIV. 

Fig.  271.  Ordinary  Electrodes. 
"     272.  Non-polarizable  Electrode  in  Bearer. 
"     273.  Ends  of  Non-polarizable  Electrodes. 
"     274.  Kronecker's  Forceps. 
"     275.  Marking  Lever. 

"  276.  Diagram  of  Apparatus  for  Studying  the  Effects  of  Electrotonus  or  Ir- 
ritability. 

PLATE  CV. 

Fig.  277.  Recording  Tuning-fork. 

"     278.  Diagram  of  Muscles  of  Thigh  of  Frog. 

"     279.         "         "    Muscle  Curve. 

"  280.  Muscle  in  Trough  bearing  Levers,  to  show  the  Wave  of  Muscular  Con- 
traction. 

"  281.  Another  arrangement  of  the  Levers  to  show  the  Wave  of  Muscular 
Contraction. 

PLATE  CVI. 

Fig.  282.  Diagram  of  the  Curve  of  Tetanus. 
"     283.  Curve  of  Tetanus,  showing  individual  Contractions. 
"     284.   Curves  illustrating  Extensibility  of  a  Muscle  during  Tetanus. 
"     2S5.  Muscles  and  Nerves  arranged  for  the  Experiment  of  the  Rheot 
Frog. 

PLATE  CVII. 

Fig.  286.  Sir  W.  Thomson's  Galvanometer  and  Scale. 

"     287.  Galvanometer  Shunt. 

"     288.  Diagram  of  "  Natural  "  Current  in  Muscle. 

"     289.  Arrangement  of  Nerve  on  Non-polarizable  Electrodes. 

"     290.  Diagram  illustrating  Electrotonus. 


LIST   OF   ILLUSTRATIONS.  xin 


PLATE  CVIII. 

Fig.  291.  Muscle  and  Nerves  arranged  to  show  Use  of  Electrotonic  Changes  in 
one  Nerve  as  a  Stimulus  for  another. 
"     292.  Apparatus  to  show  the  Effects  of  varying  Temperatures  on  a  Muscle. 
"     293.  Induction  Apparatus  of  Du  Bois  Reymond. 
"     294.  Scheme  of  Du  Bois  Reymond's  Induction  Coil. 

PLATE  CIX. 

Fig.  295.  Diagram  of  Nervous  System  of  Frog. 
"     296.  Brain  of  Frog  seen  from  above.  , 

"     297.   Commutator. 

PLATE  CX. 
Fig.  298.  Rheochord. 
"     299.  Double  Key. 
"     300.  Du  Bois  Reymond's  Key. 

PLATE  CXI. 
Fig.  301.  Creatine  Crystals. 
"     302.  Creatinine     " 

"     303.  Nitrate  of  Hypoxanthine  Crystals. 
"     304.   Hydrochlorate  of  Xanthine     " 
"     305.  Uric  Acid  Crystals. 

PLATE  CXII. 

Fig.  306.   Starch  Granules. 
"     307.  Nerves  of  Sub-maxillary  and  Sub-lingual  Glands  of  Dog. 
"    308.  Veins  of  Sub-maxillary  Gland. 

PLATE  CXIII. 

Fig.  309.  Nerves  of  Sub-maxillary  Gland  of  Dog. 

PLATE  CXIV. 

Fig.  310.  Parts  exposed  in  Operations  on  the  Sub-maxillary  Gland. 
"     311.   Gastric  Canula  seen  in  Section,  and  Key. 
"     312.  Taurine  Crystals. 
"     313.  Hippuric  Acid  Crystals. 

PLATE  CXV. 
Fig.  314.   Cholesterin. 
"     315.   Bernard's  Instrument  for  puncturing  Fourth  Ventricle. 
"     316.   Section  of  Rabbit's  Head,  showing  direction  of  Instrument  in  order  to 
puncture  the  Fourth  Ventricle. 

PLATE  CXVI. 

Fig.  317.   Canula  in  temporary  Pancreatic  Fistula. 
"     318.  Diagram  to  show  arrangements  of  Stitches  in  Thiry's  Fistula 
"     320.  Milk  Globules. 
"     321.   Colostrum. 

PLATE  CXVII.  * 

Fig.  322.  Urea. 
"     323.  Nitrate  of  Urea. 
"     324.  Oxalate  " 

"     325.   Blowpipe  Flame. 

"     326.   Glass  Tube  drawn  out  to  form  a  Pipette. 
•'-"•  "         in  order  to  seal  it. 

Beaker  supported  on  Wire  Gauze  to  prevent  it  from  Cracking. 
'     320.   Apparatus  to  prevent  Loss  by  Evaporation  during  prolonged   Ebulli- 
tion. 


XIV 


LIST   OF    [LLUSTR  VTIONS. 


PLATE  CXVIII. 

Fig.  330.  Saucepan  used  as  Water-bathi 

331.  Bnnsen's  Gas  Regulator  aa  modified  by  Geiasler. 

"     332.  Water-bath  for  evaporating  nl  a  constant  lemperatnre. 

"     333.  Use  of  Syphon  in  Washing  Precipitates. 


PLATE  CXIX. 

Fig.  334.   Screw-press. 
"     335.   Bunsen's  Water  Air-pump. 

33(3.  Plantaraour'fl  Funnel  for  keeping  Fluids  Hot  during  Filtration. 


337    Dialyser  of  Gutta-percha 


PLATE  CXX. 

Fig.  338.  Dialyser  suspended  in  Water. 

"  339.  Hot-air  Bath. 

"  340.  Ball-jar  and  Dish  for  drying  and  cooling  Substances. 

"  341.  Method  of  drying  Precipitates. 

"  342.  Platinum  Triangle  for  Ignition. 

"  343-4.   Specific  Gravity  Bottles. 

"  345.            "             "            "         for  small  Qiantities  of  Fluid. 


Fig.  346.  Measuring  Flask. 
'«     347.  Test  Mixture. 


Fig.  348.   Pipettes. 
"     349.  Mohr's  Burette. 


PLATE  CXXI. 


PLATE  CXXII. 


PLATE  CXXIII. 

Fig.  350.   Stand  for  Burettes. 
"     351.  Elliptical  Appearance  of  Surface  of  Liquid  in  Burette. 
"     352.   Erdmann's  Float. 
"     353.   Saccharometer. 


NOTE 


The  letter-press  descriptive  of  the  illus 
to  specific  pages  of  the  text.  Inasmuch 
that  of  the  English  edition,  we  subjoin  a 
of  the  two  editions  is  seen  at  a  glance. 


trations  in  this  work  contains  references 
as  the  paging  of  this  edition  differs  from 
table  in  which  the  corresponding  paging 


Plate  I. 

F.ng.  Ed. 

Am.  Ed. 

Eng. 
Plate  XX. 

Ed. 

Fig.      1, 

page       6,      see    page     22 

Fig     59,     page 

49, 

"        2 

"        14, 

31 

Plate  XXI. 

Plate  II. 

Fig.    60, 

50, 

Fig.      4, 

"        11, 

"        26 

Plate  XXII. 

Plate  III. 

Fig.    61, 

50, 

Fig.      5, 

16, 

31 

Plate  XXIII. 

6, 

17, 

"         "        33 

Fig     42, 

50, 

Plate  IV. 

Plate  XXIV. 

Fig.    11, 

"         42, 

'         "        56 

Fig.    63, 

53, 

"      19, 

"       10S, 

'         "       121  • 

"      61,         " 

61, 

Plate  V. 

"       15,         " 

56, 

Fig.    22, 

3, 

"        19 

"       65,         " 

51, 

"      23, 

"          5,        ' 

'         "         21 

Plate  XXV. 

"      21, 

"       13-15, 

'        "      2S-31 

Fig.    68, 

61, 

Plate  VI. 

'•       67, 

52, 

Fig.    2.5, 

9,         ' 

'         "         25 

Plate  XXVI. 

11         7, 

"        23, 

38 

Fig.    69,        " 

72 

Plate  VII. 

"       70, 

72, 

Fig.    2(5, 

"        27          ' 

42 

Plate  XXVII. 

"      28, 

2t, 

41 

Fig.    71, 

60, 

Plate  VIII. 

"       73, 

78, 

Fig.    30, 

"    29-112,     ' 

"      44,  125 

"       74,         " 

78, 

Plate  IX. 

Plate  XXVIII. 

Fig.    33, 

33, 

47 

Fig.    72,        " 

1  o, 

"      31, 

"         29, 

'         "        44 

"       75,         " 

78, 

Plate  X. 

Plate  XXIX. 

Pig. 

28, 

43 

Fig.    70, 

78, 

Plate  XII. 

"      77, 

73, 

Fig.    30, 

38, 

52 

Plate  XXX. 

"       40, 

40, 

54 

Fig.     79,         " 

7S, 

Plate  XIII. 

"       7S, 

78, 

Fig.    42, 

"      41, 

Plate  XV. 

41, 

3S,         ' 

52 

Plate  XXXI. 
Fig.    80, 

"      81, 

7>, 
78, 

Fig.    4S, 
"       40, 

44, 

46,         ' 

5S 
00 

Plate  XXXII. 

Plate  XVII. 
Pig     53, 

41, 

5S 

Fig.    S3, 

"      S2, 

78, 
78, 

"    s*, 

41, 

"        58 

Plate  XXXIII. 

8, 

33,         ' 

47 

Fig.    81, 

77, 

XVIII 

"      S6, 

78, 

Fig. 

3  J, 

<        «        48 

Plate  XXXIV. 

Plate  XIX. 

Fig.    87, 

70, 

Fig.    :/■,, 

40, 

"        63 

"     8S, 

82, 

66 

7t 
69 
67 

74 
6.5 

So 
85 

S2 
91 
91 

82 
91 

91 
SO 

91 
91 

91 
91 

91 
91 

91 
91 

92 
95 


XVI 


NOTE. 


Eng. 

Ed. 

Am.  Ed. 

Eng 

Ed. 

An,    E.I. 

Plate  XXXV. 

Plate  LXI. 

Fig.    i 

60,      boo    page     91 

1'ii.'.  130,     page 

120,      gee    page     133 

Plate  XXXVI. 

"    132, 

120, 

"       133 

Fig.  90-fll      " 

83, 

98 

"    133,        " 

12o, 

" 

"      92, 

83, 

96 

Plate  LXI  I. 

Plate  XXXVII. 

Fig   134,        " 

126, 

"        139 

Fig.    93, 

79, 

'         "        92 

"     135, 

120, 

ii 

"        9, 

37-S3, 

"     51,96 

Plate  LXIII. 

PLATE  XXXVIII. 

Fig.  136,        " 

124, 

" 

Fig.    94, 

83, 

96 

"     137, 

124, 

"       137 

"    13S,         " 

122, 

"         " 

Plate  XXXIX. 

Fig.    97, 

79, 

'        "        '.'  2 

"    ,39'         " 

120, 

"       133 

"      9S, 

118, 

"      131 

Plate  LXIV. 

Plate  XL. 

Fig   140, 

125, 

"      133 

Fig.    99,         " 

106, 

"      119 

"     141, 

126, 

"      139 

"      100,           " 

106, 

"       119 

Plate  LXV. 

Plate  XLI. 

Fig.  1 13, 

134, 

"        146 

Fig.  103, 

105, 

'        "      118 

"     142, 

l-;, 

"        139 

"     141,         " 

134, 

"       146 

Plate  XLIII. 

Plate  LXVI. 

Fig.  105}         " 

12-3, 

"      139 

Fig.  145,         " 

134, 

"       146 

Plate  XLIV. 

Plate  LXVII. 

Fig.  109,        " 

28, 

"        43 

Fig  146,        " 

132, 

ii       ]U 

"    109,        " 

115, 

"      128 

"     14S,         " 

132, 

"       114 

Plate  XLVI. 

"     149,         " 

132, 

"      U4 

Fig.  Ill,        " 

112, 

"      125 

Plate  LXVI1I. 

•       "    112, 

112, 

"      125 

Fig.  150,         " 

132, 

ii      1U 

Plate  XLVII. 

"     151, 

131, 

"      ill 

Fig  113, 

112, 

"      125 

"     152,         " 

131, 

"       144 

Plate  XL VIII. 

Plate  LX IX. 

Fig.  115, 

111, 

"      12.) 

Fig.  153, 

137, 

"       149 

"    114, 

112, 

"      125 

"     154, 

132, 

"       144 

Plate  L. 

Plate  LXX. 

Fig.  117, 

114, 

"      127 

Fig.  156,        " 

13S, 

"      150 

"     IIS,         " 

114, 

"      127 

"     15S,          " 

142, 

"       154 

Plate  LI. 

Plate  LXX  I. 

Fig.  119,         " 

114, 

ii      127 

Fig.  159,        " 

14S, 

"         "      159 

"     160,        " 

14.3, 

"       159 

Plate  LI  I. 

"     161,         " 

US, 

l.V) 

Fig.  120,        " 

114, 

"      127 

ii     102)         " 

148, 

"       159 

Plate  LI  1 1. 

"     163,         " 

14S, 

"      159 

Fig.  121,        " 

115, 

"      128 

Plate  LXXII. 

Plate  LIV. 

Fig.  163-1 72,  " 

152, 

'•         "      163 

Fig.  122, 

115, 

'        "      12S 

Plate  LXXIII. 

Fig.  173,         " 

153, 

"        "      164 

Plate  LVI. 

Fig.  124, 

114, 

ii      127 

Plate  LXXV. 

Fig.  178, 

156, 

" 

Plate  LVII. 

Plate  LXXVII. 

Fig.  125, 

114, 

"      127 

Fig.  183,        " 

157, 

"        "      16S 

Plate  LX. 

Plate  CX. 

Fig.  129,        " 

117, 

"         "       130 

Fig.  298,        " 

347, 

"        "      354 

Plate  I. 


FIG.  i. — Simple  arrangement  for  warming  an  object  under  the  microscope.  It  consists  of  a  copper 
plate  (c)  with  a  central  orifice  which  is  cemented  to'a  common  object-glass.  From  the  edge  of  the 
plate  a  copper  rod  (g)  projects,  the  end  of  which  can  be  heated  by  a  spirit  lamp.    p.  6. 

FIG.  12.— A  similar  but  more  complicated  apparatus.  The  copper  plate  6  is  square.  The  rod  e 
projects  from  its  under  surface  (upper  as  seen  in  the  drawing),  and  fits  in  a  groove  cut  in  the  glass. 
The  groove  ends  in  a  hole  into  which  the  pin  d  fits. 


FIG.  2.— Strieker's  warm  stage  (simple  form).  It  consists  of  a  block  of  black  vulcanite  about  3 
inches  long  by  VA  wide,  and  %  inch  thick.  The  central  chamber  (4)  is  closed  below  by  a  glass  plate, 
and  surrounded  at  the  top  by  a  perforated  copper  dish  («),  the  orifice  of  which  is  of  the  same  size 
as  the  chamber.  The  chamber  is  cylindrical.  The  cistern  of  the  thermometer  surrounds  the  cham- 
ber, as  shown  by  the  dotted  line  Id).  Its  capillary  tube  lies  in  a  trough,  one  side  of  which  is 
formed  by  the  back  of  the  block  and  the  other  by  a  metal  plate  screwed  on  to  it,  the  form  of 
which  is  shown  in  the  figure.     The  tube  (r)  leads  into   the  chamber.    A  second  tube  leads  from  it 

through  tin-  proji  ctinj  Ilic  arm  shown  at  the  tup  of  the  figure.    This  arm,  which  is  of  one  piece 

witli  the  disk  In),  is  of  such  size  that  the  rod,  tig.  13,  fits  on  to  it.  By  means  of  this  rod  the  chamber 
is  heated  in  the  way  already  explained,  In  experiments  with  gases  the  gas  enters  by  c  and  passes 
out  through  the  projecting  arm.     p.  14. 


FIG.  13.— A  rod    <7)  Intended  to  lit  on  the  projecting  arm  of  fig.  2  by  means  of  a  spiral  (/).    It 
answers  the  same  purpoM  al ';/'  in  tit-,  t.    A  ilmllar  but  much  lighter  rod  is  used  for  fig.  12. 
fig.  16.  object  rapport  "i  I  measuring  finches  by  1,  with  central  gas  chamber  a, 

.  ,.    1.  1,  .      I  hi    block    when    in  use  is   fixed  with  putty  on  to  an 
ordinary  object-glass,  and  the  chamber  clo»ud  .it  the  Urn  with  a  cover-glass. 


Plate  II. 


FIG.  3. — Strieker's  warm  staee.  In  the  vessel  ABC  the  water  is  maintained  at  a  constant  level  {indicated  by  the 
dotted  line),  and  at  boiling  temperature.  A,  supply  tube  ;  B.  waste  tube ;  0,  tube  leading  to  the  stage ;  D,  tube  by 
which  the  hot  water  leaves  the  stage,  terminating  in  a  conical  dropper,  E  ;  F,  funnel  for  collecting  the  drops  which 
fall  from  E;  G,  waste.  The  rate  of  flow  is  determined  by  varying  the  height  of  E,  by  means  of  the  sliding  screw  ou 
which  it  is  supported  It  admits  of  more  exact  adjustment  by  means  of  a  fine  screw  which  works  in  the  axis  of  the 
vertical  column,  on  which  the  escape  tube  is  supported.  This  column  is  firmly  fixed  in  the  stage  of  the  microscope  ; 
its  axial  screw  terminates  above  in  a  milled  head,  K. 


FIG.  4.— Capillary  pipette,    p.  11. 


Fig.  n—  A  similar  stage  by  Strieker,  in  which  the  chamber  b  is  warmed  by  a  voltaic  current,   //are  two 

topper  plates  u,  which  Strieker's  electrodes,  represented  in  Bg. '.,  an  applied,     .■    a  platli wire  by  which  these 

two  plates  are  iii  communication.    It  coils  round  the  obtern  "f  the  thermometer  d.    The  electrodes  are  in  connec- 
tion with  the  opposite  pules  of  a  suitable  battery,  the  elements  ol  which  mu>-t  present  a  large  surface. 


PtATE    III. 


FlO.  s.— Carbonic  acid  apparatus.  A.  Bottle  containing  hydrochloric  acid.  M.  Bottle  containing  fragments  of 
marble  on  a  stratum  of  broken  glass.  V.  Wash-bottle.  H.  Object  support,  fig.  16.  G.  T-tube  which  communicates 
with  the  gas  ai>pajatus  by  the  tube  F,  which  is  guarded  by  a  clip,  and  in  the  opposite  direction  with  H.  By  its  stem 
it  is  in  direct  communication  with  the  mouth  of  the  operator  by  a  tube  on  which  there  is  also  a  clip.  When  the 
first  clip  is  closed,  carbonic  acid  collects  in  M  and  drives  back  the  hydrochloric  acid  into  A ;  a  current  of  air  can 
then  be  drawn  through  G  and  H.  If  the  clip  on  the  mouth-tube  is  closed  and  that  on  F  opened,  carbonic  acid 
passes  through  H.    p.  i6. 


Via.  &— Microscope  stage  on  which  the  object-glass  is  held  ill  position  by  Strieker's  electrodes.     Each  electrode 
■  i  by  being  screwed  Into  aii  ivory  knob  which  is  let  into  the  stage  plate  of  the  microscope.    The  electrodes 
are  connected  (with  the  Interposition  of  a  key)  with  ti.e  secondary  coil  of  a  Dm  Bois  Beymond'e  induction  appa- 
ratus.   The  key  i-  i'  pi'   'lit.  'I  open.    The  upper  surface  of  the  object-glass  is  covered  with  tinfoil,  leaving  a  apace, 
ft,  for  the  reception  of  the  object,    p.  17. 


Plate  IV. 


FIG.  ii.— Support  for  the  study  of  the  circulation  in  the  web  of  the  frog.  It  must  be  so  arranged  that  the  large 
hole  is  just  opposite  the  stage  aperture  of  the  microscope.  {See  description  in  text,  p.  42.}  It  may  also  be  used  for 
the  study  of  the  tongue.  For  this  purpose  half  of  a  ring  of  cork  must  be  fixed  with  brass  pins  round  the  hole  on 
the  side  next  the  end  of  the  board.    To  this  cork  the  cornua  of  the  tongue  may  be  attached. 


FIG.  20. — a  A  b.  Injection  cannulas,  actual  sizes. 

Fig.  21.— Section  knife.    In  the  left-hand  corner  transverse  section  of  the  blade. 


Fro.  18,— Nozzle  of  injection  syringe,  actual  size. 

Fig.  19.— Support  for  mudying  the  circulation  in  the  mesentery  of  the  frog.  /v.  Board  on  which  the  frog  lies. 
C.  Glaus  dink  on  which  tin:  mesentery  red  6  TrOB  b  tm  tbe  reception  Of  the  coU  Of  intestine,  d,  Object-glass 
covered  with  cork.    [In  the  text,  p.'  iu£,  0  and  c  are  transposed,] 


Plate  V. 


FIG.  32.— Common  large  colourless  corpuscle  of  the  newt,  a  to  h.  Successive  forms  assumed  by  the  same 
cell  in  the  course  of  an  hour,  in  a  preparation  enclosed  in  oil,  without  the  addition  of  any  reagent,  p.  3.  (Hart" 
nack:  Ocular,  No.  3;  Objective,  No.  8.) 


Fli;.  23. — A  granular  corpuscle  in  the  same  preparation,     a  to  h.  Successive  forms  assumed  by  the  same  cell 
in  the  course  of  fifteen  minutes,     p.  5.     (Ocular,  No.  3;  Objective,  No.  8.) 


O    Q 


FIG.  24.— a  and  b.    Coloured  bl  ol    the   newt,  after  the  addition    ol   -   per   cunt,  boracic  acid. 

idiowing  tb  1     -    Coloured  corpuscle  ol  human  hi 1,  after  the  additl 1       i~  1    cent,  tannin 

■olntion,  i,  Co] 1  corpuscle  of  newt's  id 1,  ai'ti-i   ihf  aiiditioii  of  diluted 

with  water,  and  then  ■objected  to  the  action  ol  COa.   ,/'.  The  same,    a  small 

CO  It  had  ■ endered  pale  by  treatment  with  water.    </.  Colourless 

dilute  acetic  acid.    7«.  Colourless  corpuscle  of  human  blood,  after 
the  addition  of  dilute  acetic  acid,      pp.   13-15.     (Oc,  3;  Obj.,  8.) 


Plate  VI. 


FIG.  25. — Oil  preparation  of  human  blood,  as  observed  on  the  warm  stage.    A  colourless  blood  corpuscle  is 
seeu,  showing  the  changes  of  form  it  has  undergone  in  twenty  minutes,     p.  9.     (Hartuack:  OcuJ.,  3;  Obj.,  8.) 


Pi<;  7.— Varlotu  tormi  of  epithelial  oelli  fr  <.m  the  trachea  "f  test,  tttt  1  of  bichromate 

of  |».U»I.      '.  to  th«  left,     p.  -.1.     Ill,-,   i,  Obj.,  8.) 


I'LATE    VII. 


FIG.  26.— Epithelial  cells  from  the  urinary  bladder  of  a 
rabbit,  after  maceration  in  solution  of  bichromate  of  potash 
p.  27.     (Oc,  4;  Obj..  8.) 


m!k 


'-■;i 


',':,/ 


J9B 


Via. 27.— Epithelial  cells  didged cells)  of  the  rote  malpigliii  from  a  pjiuted  condyloma,  macerates  in  sjlution 
of  bichromate  of  1  Ua  are  in  various  stages  of  division.   (Oc,  3 ;  Obj.,  8.) 


I 

1  ■'     the    Jni'l<ll>!    I:  .lit    .  |.i  thtl  I  UKl     froll 

Obj.,  h.) 


vertical    action  01  tbt 


Plate  VIII. 


Fl<i.  go.— Abdominal  surface  x,t  centrum  tendinenm  of  rabbit,  slightly  coloured  with  silver,  a.  Endothelium 
of  the  seros*  where  no  lymph  vessel  is  seen.  b.  The  same,  showing  an  interfascicular  lymph  channel  under- 
lying the  endothelium,  in  which  a  capillary  lymph  vessel  runs.    c.  A  "stoma"  (?).   pp.  29,  112.    {Oc.,2;  Obj.,  4.) 


. 


I 


m 


FIG.  31.— Pleural  surface  of  centrum  tendineum  of  rabbit,  more  strongly  coloured  with  silver,     a.   Dark  silver 
lines  of  the  interstitial  substance  of  the  endothelial  cells ;  0.  cell  substance ;  c.  nucleus.    (Oe.,  3;  Obj.,  5.) 


Via.  32,— The  iome  aa  fig.  30,  kUH  more  Intensely  colotued.    (Oc.,   \\  Obj.,  71 


Fm.  33—  Omentum  of  guineapig  treated  with  silver.  A.  One  of  the  principal  trabecular,  containing  blood 
vessels  and  fat  cells,  n.  Fenestrated  portion,  the  trabecular  of  which  are  covered  with  flat  endothelium,  p.  33, 
where  it  is  referred  to  as  fig.  8.    (Oc,  3;  Obj.,  7.    Tube  of  the  microscope  not  drawn  out.) 


• 


^ 


torn  ol 

the  endothelium  which  00  |  rah  1    li  [8>.    11  re  and  there  cells  at in  which  have  germlnatlre 

characters;  ami  branded  cells,    a.  Meshwo'-k  of   trundles  of  fibrous  connective  tissue,    p.  29. 


Plate  X. 


^ 


FIG.  35. — A  similar  preparation    ir,..Lu   the  same  omentum  as  fig.  34,  showing  groups  of  germinating  endothe- 
lial cells  amongst  the  ordinary  large  endothelial  elements  which  cover  the  trabecula  (6). 
(In  Figs.  34  and  35,  Oc.  3,  Obj.  5.    Tube  half  drawn  out.) 


/»> 


x^%-. 


Yv.  -j,  11. .11  of   the  teptnm  ■  •/  tbi  eUterna   IpmpJtatiea   magna   In  a,  Bndo> 

uumte  ot  peril  •!"   i  mrtace  having  germinating  character!,    fc.  A  tree  trabecula  projecting  above  t/..- 

rarfaee,  severed  tbeUonj     t    Pigment  celli.    p  [Oi  Obj.,  8,    Tube  do!  drawn 


Platk  XI. 


FIG.  38. — Bud-shaped  structure  of  uiesogastriuin  of  frog,  treated  with  silver,  covered  with  ciliated  polyhedral 
germinating  endothelium.  In  the  ground-substance  of  the  bud-shaped  structure  are  groups  of  young  amoeboid 
cells;  and  in  addition  to  these  are  vacuole  cells  beset  with  cilia  on  their  internal  surface— i.e.  that  turned 
towards  the  cavity  of  the  vacuole.  There  is  also  a  large  vacuole  cell,  the  wall  of  which  has  become  changed 
into  endothelium.    (Oc,  3;  Obj.,  8.) 


7.— Stiver  preparation  of  fenestrated  portion  oi  anterior  mediastinum  in  the  1  ri        ben         germtnatli 

Obf.,  7-1 


Plate  XII. 


—Horizontal    prepara'ion  of  cornea  of  frog  coloured  with    chloride  of    gold,  showing  the  network  of 
branched  cornea  corpuscles.     The  ground-substance  is  completely  co'ourlesB.    p.  40,  referred  to  as  fig.  10.    (Oc.  3; 

obj.,  a) 


iX 


$m&-<  ■rV  I 


1.  ( malty$tem).    1 place 

1     in  wen  ;  in  two  othei  1   11 uwUcolai 

1  1 !■>  which  sonnacl   the 

(0           Obj.,  /.    Immenion.) 


Plate    XIII. 


FIG.  42.— Membrana  nic titans  uf  frog,  treated  with 
chloride  of  gold.  a.  Branched  pigment  cells.  6. 
Unpigniented  portion  of  the  body  of  the  cell. 
il.  Depigmented  process.  c.  Nucleus  of  pigment 
cell.  e.  Ordinary  unpigmented  branched  flattened 
cell.  p.  41.  (Oc.,  4;  Ohj.,  10;  immersion — reduced  to 
11  ilf.) 


FIG.  43— Surface  of  chronically  inflamed  me- 
sentery of  ape.  peucilled  ana  treated  with  silver. 
Canalicular  system  :  Migratory  cells  are  seen 
upon  the  flat  branched  cells,  which,  on  account 
of  their  nuclei  and  size,  are  probably  not  to  be  re- 
garded as  colourless  blood  corpuscles.  (Oc,  3; 
Obj.,  8.    Tube  not  drawn  out.) 


FIO.  44.— The  same  preparation,  showli  the  canal         ,        ,     .  ailed  with  fat  globules 

m  of  cornea  of   .  I  first  with  lunar  caustic,  and  afterwards  placed 

I 11  I"  .1  oul    l>y  a  dark 

granular  pi  1  that  shown  In  Bg.    ..    I  l  ■■■  on  ■     1  ich  other  as  the 

photograph,    p.         (0  Obj.,  7.    Tube  not  drawn  out.) 


Plate  XIV 


of    infni.-orl.ital   fossa   of   rabbit,  freshly  prepared  in  serum,     a.    Bundles   of 
connective  tissue.    I.  Flat  branched  cells,    c.  The  same  seen  in  profile,    d.  Cells  of  doubtful  character 


1  i  on  the  lurface.     i 

luictly  (ibrill  ,i 


Plate  XV. 


V 

PIG.  43.— The  same  cells  as  in  fig.  47  being  converted  into  fat  cells,    p.  44.    (Oc,  3;  ObJ.,  9  ;  immersion.) 


■   ol    gravid    uterus   of   sow,  maceialed   in  bichromate  of   po1 
Blanched  cells,  more  or  loss  spindle-shaped.     b.  Bundles  of  connective  tissue,    p.   46.    (Oc,  3;  Obj.,  8.    Tube 
lialf  drawn  out.) 


,  tal  peritoneum  from  thelnmbai  region  of  a  rabbit  with  chronic 

tive  tissue  COt] 
ObJ.,  8.) 


Plate  XVI. 


i  i  [  omentum    of    rabbit,    pencilled    and   treated  with    silver,     a.  The   flat 

branched  granular  structnn  .  fch  b  nuclei  art     narplj 

defined,   and  In  .,,.!,        &.  Migratoi 

free,  irhile  othen  grow  '">*•  ""|"  the  flat  celJ    ol  the  canalicular  syi  ben  latter,  the 

formation  of  a  vacuole  La  seen  at  c.    d.  II    the  wall  "f  which   i  ad  Into  endothelial 

[Oc,  3  ;  ObJ.,  9,     f  in i< 


Plate  X. 


FIG.  35. — A  similar  preparation    from   the  same  omentum  as  fig.  34,  showing  groups  of  germinating  endothe- 
lial cells  amongst  the  ordinary  large  endothelial  elements  which  cover  the  trabecula  (b). 
(In  Figs.  34  and  35,  Oc.  3,  Obj.  5.    Tube  half  drawn  out.) 


,  .   preparation  ■•(   the  leptnin   ol   tbi  eliterna   lymphatica   magna   In  1 1    Endo 

having  germinating  character*.    i>.  A  bee  trabecula  projecting  above  the 
covered  with  germinating  endothelium,    0    Pigment  culls,    p.  -•«.    (Oc,  ;;  Ob].,  8.    Tube  not  drawn 


Platk  XI. 


FIO.  38.— Bud-shaped  structure  of  mesogastrium  of  frog,  treated  with  silver,  covered  with  ciliated  polyhedral 
germinating  endothelium.  In  the  ground-substance  of  the  bud-shaped  structure  are  groups  of  young  amoeboid 
cells;  and  in  addition  to  these  are  vacuole  cells  beset  with  cilia  on  their  internal  surface— I.e.  that  turned 
towards  the  cavity  of  the  vacuole.  There  isjilso  a  large  vacuole  cell,  the  wall  of  which  has  become  changed 
into  endothelium.    (Oc,  3;   Obj.,  8.) 


, 


I  rated  portion  oj     aterioi  mediael  i In  tbe  cal     e  ten  prminatfoa 

101    ial]     ">■       ■  ■   Obi.,  7-> 


Flate  XII. 


-Horizontal    prepara'ion  of  cornea  of  frog  coloured  with    chloride  of    gold,  showing  the  network  uf 
branched  cornea  corpuscles.     The  ground-substance  is  completely  co'ourless.    p.  40,  referred  to  as  fig.  in.    (Oc  3; 

obj.,  a  > 


1  a.  Canallcul 0  analiyittm)     h place 

■  branched,  Battened  conn  1     i»  wen;  in  two  other    ar<   lacuna  ol  the  canalicular 

corpuscle*.  <f.  Migratory  cell      i    Branched  channel)  which   connect  the 

(  the  canalicular  eyetei  dark     p  |Oi  Ob]     1     1 lei  Ion.) 


Plate    XIII. 


-^ 


Fig,  45.— Ordinary  fat  cells  of  a 
fat  tract  in  the  omentum  of  a  rat. 
(Oc,  3;  Obj.,  7) 


FIG.  42.— Menibrana  Qictltane  of  frog,  treated  with 
chloride  of  gold.  a.  Branched  pigment  cells.  6. 
Unpigmented     portion    uf     the    body    of    the     cell. 

d.   Unpigmented    1 :ess.      c.    Nucleus    of    pigment 

cell.  c.  Ordinary  unpigmented  branched  flattened 
cell.  p.  41.  (Oc,  4;  Obj.,  10  j  immersion— reduced  to 
about  half.) 


FIG.  43.— Surface  of  chronically  inflamed  me- 
sentery of  ape,  pencilled  an  A  treated  with  silver. 
Canalicular  system  :  Migratory  cells  are  seen 
upon  the  flat  branched  cells,  which,  on  account 
of  their  nuclei  and  size,  are  probably  nut  to  be  re- 
gar  ltd  as  colourless  blood  corpuscles.  (Oc,  3; 
Obj.,  S.    Tube  nut  drawn  out.) 


'  Uw  eanallculai  ,yrt<  m  Oiled  with  Cat    lol 

irda   placed 

rim  tm  •■ :""!''1    ■  1 1 

(noolu  p  md  that  thown  tberaathe 


oi>j..  7.    Tube  Dot  'Ira 


Plate  XIY. 


FIG.  46.— Gelatinous    substance   01    infra-orbital    fossa   of   rabbit,  freshly  prepared  ill  seiiim.     a.    Bundles    of 
connective  tissue,    b.  Flat  branched  cells,    c.  The  same  seen  in  profile,    rf.  Cells  of  doubtful  character 


'  from  the  surface.    They  appeal  rithoblonj 

tinctly  ilbrili  ■■  b  then  figure*.) 


Plate  XV. 


PIG.  40 — Portion   of   submucous  tissue  of    gravid    uterus   of   sow,  maceiated 
Branched  cells,  1  ped      b.    Bundli     oi  connective  tissue. 

hall  drawn  out.) 


bichxoiuate  of  potash.     *r. 
46.    (Oc,  3;  Obj.,  8.    Tube 


I 

11.. 1.    ,    1. 


Plate  XVI. 


if 


I  [  omentum    of   i   obit,    pencilled    and  treated    with   silver,     a.  The   Sat 

i     ■  b     finely    granular  .  I  racl  tiri    :  their  am  li  I  are    barplj 

of  'li\  Idlog.     /..   M  l|  rat  ore    of    it  bich   are 

free,  while  othen  grow  out  from  ili.r  flat  celli  of  the  cai  m,  i  one  of   the  latter,  the 

formation  ..f  a  \  i    U    lis     roll  of  which   i,  alreadj  changed  Into  endothelial 

elemeuU.    (Oc.,  '\\  oi.j.,  9.     Inn 


Plate  XVII. 


I        11       ti.      I 


Fig.  52.— Caudal  tendon  of  a  young 
treated  with  silver.  The  spaces  occup 
cells  are  clear,  while  the  intercellula 
stance  is  seen  as  dark  lines. 


itcr.-titial   sub- 


FIG.  53.— Similar  pre]  aration  from  a  full  grown 
at.    p.  44-    (Oc  j  ;  Obj.,  7.) 


(.1,.    54.— Caudal  tend >'  young  rat,  treated  first  with  dilute  acetic  acid,   and   then  with  chlori 

the  arrangement,  form  and  structure  of  the  tendon  cells,    p.  44.    (Oc,  2;   Obj.,  8.) 


--Tniiisvi-r-e  aecMon  of  tendon  from 

at  250.) 


m  of  11 
Bundli  ■        ■  ! 


Plate  XVIII. 


FIG.  #.— Network  of  elastic  fibres  from  the  fresh  mesentery  of  i 
a  the  network  is  more  superficial  than  in  6.    p.  34.    (Oc,  3;  01>j., 


rabbit,  treated 
7) 


itll    dilute   acetic   acid.      I  I 


PIO.  57.— Longitudinal   section   ..f   Intervertebral  cartllag.    -1    thi  tall  of   a    rabbit.     Tb<     preparation    was 

■olonied   with   chloride  <>i  gold,  then   macerated  in  dilute  chromic  acid,   and    hardened  mi  alcohol.     '/.  Clear 

irtilage.     "     Border  between  hyaline  and  (e)  1  1  1  cartilage       Heri    thi     (ro 1    ubsti ■ 

tendon)  of  bund  1.    ae.     instead  ■■<    flai    tend ells,   an    otheri    whichtt 

a   ol   1 1. ni  1 and     Iructnral  ehajrac 

led  a*  cartilage  cells.    "*, 


Plate  XIX. 


"^SSft^^fc 


^ 


<?\ 


piphysig  in  the  neighbourhood  of  the  diaphysis  of  the  femur  of 
;i  human  ■  till  covered  with  hyaline  cartilage,     a.  Superficial 

portion  of  hyaline  cartilage.    6.  The   . i,  with  lai  i  ubatance  of  which  ate  is 

e.    d.  Fine  fibrous  tiaaue,  rich  in  cell  elements  and  bl 1- 

work  of  Hie  bone  trabecules,    p.  49.    (Oc,  •.;  ObJ.,7.) 


Plate  XX. 


io>:M?i: 


»)i^.'«**  ,t: 


i  epiphysis  of  the  same  preparation.    \  and  B.  Porehyalli artlloge  ■  ■(  the  Joint. 

■  •■•<   ■   "i  I.e.,  where  U     Hi b  i  I    diminished- 

,\t  i>  the  cellelen 

order  peripherally ;  the  Intercello  U  farther  dixoli  i   Into  Don j  trabe 

embryonal  bone  I  I  !        i  ! e  apace*,  which  answer  to  the  cartllagi 

oayadM  <rf  the  previous  layer  D.hs  ,,.  ,.,.    (0o.,4;  ObJ.,  j     Tube  not  drawn 

out.) 


Plate  XXI. 


!>Vi 


1$i^iSm 


QW:*f$. 


^■■«/. 


PIO. 60.— Transverse  flection  ot  the  dlaphysia  of  thefei anUma \,  macerated  with  chromic  acid,  a.  Con- 

cc-utri«:  |.-i  '■  urn      >>     I: lies  nf  connective  tissue  uj'  the  periosteum  which  run 

longitudinally,  cat  across,    c.   Loose  la] Lnflei  oal  periosteum,  rich  is  blood-vessels  and  young  cellsi  which  is  in 

on  into ''.  the  Arab  0  its  rich  medullar;  tissue.    The  latter  alum  mis  in 

md  and  between  the  trabecule.    The  cells  of  the  loose 

tissue  ut  1  I'cll    (1 ■■■•■>  Tii     I-m)  lumul  in  the  bone  tra« 

becukv,  «-.*■■                                                                      trabecules,  and  with  those  in  the  medullary  tissue.    In;* 
similar  manner  tin  I  periosteal  layer  (more  or  less  distinct  fibrous  con- 

nective tissue)  are  continuous  with  that  of  tin  il»,  and  of  the  spaces  between  them*    p.  50,    (Oc.,3i 

ObJ.,5.    Tuhhah  drawn 


Pl.ATF,    XXII. 


<-  &r£? 


^y 


'2  if 

S>,  .  o' 


^rv-r^ :         ,  lip 

k'^'.*       ,1.    XI.  P..    ...  ^jf    ':'«     ,-    ,        1 


FIC.  6r.— Vertical  section  of  the  parietal  bone  of  tlie  sknll  of  a  child,  macerated  in  chromic  acid,  showing  the  bone 

Izabecuta  of  the  diploe.   a.  B i  trabecule,  covered  bj  [e)o  teoblasts.   e.  Medullary  tissue  (in  outline),  d.  Spaces, 

artificially  occasioned  by  the  yielding  of  the  lamella!  of  the  bone  trabe.iike.     p.  50.    (how  power.) 


Plate  XXIII. 


wdmr 


r  5  $u#  1 


' 


1  ;  i   linal  bi  piphynitj  of  the 

1  I oi   a    rabbli     i  rated   in  chromic 

acid.    a.  1  M  b     Iht  dulla,    a'.  System  <.f 

;  an  Uled  up 
«ith  medullar;  tl  ue,  i  ii  b  to  ci  Uulai  elemenj  i  he  ■ 
element!    mednllary  celli    are  in  continuity  wiil 

■■  hich  have  a  coluuinai  arrange* 

era [es  begin 

to  enlai   ■  transii  Ion  Into  the  tubular 

L'fTllli- 

ii.ii.-.    The  intercellular  nibstance  which  bounds  the 

Ca] I,      p.       ..     I  LOU    i N    I 


Plate  XXIV. 


FIG.  63.— Longitudinal  section  of  muscular  coat  of  fallopian  tube  iu  a  sow.  a.  Connective  tissue  trabecule-  which 
form  the  septa  between  the  bundles  of  unstriped  muscular  fibre,  b.  Transverse  layer  of  unstripcd  muscular  fibres, 
cut  across,  c.  Connective  tissue  which  contains  the  large  blood-vessels,  and  separates  the  transverse  muscular 
layer  6  from  the  longitudinal  muscular  layer  d.  c.  Outermost,  or  serous,  covering  of  the  fallopian  tube.  p.  53. 
Oc,  3;  Obj.,s) 

FIG.  64.— Fresh  isolated  preparation  covered  in  serum  from  the  tail  of  a  rabbit,  showing  the  transition  of  trans- 
versely striped  muscular  fibre  into  a  connective  tissue  bundle,  i.e.,  into  tendon,    p.  61.    (Oc,  2  ;  Obj.,  5.) 


\ 

h 

/, 

0 

W* 

a. 

w 

Fig.  15. — Diagram  t,,,  llhutrate  the  ■ 
a  ray  of  lighl  transmitted  tin    a 
fibre.    18m 


'lated  nil  unlaj  Sbrt  ■><  Bydrophllu 
a.  Muncular  labetaace.    (.  Entering  non-medullary  nerve  fibre,    c.  Doyore'   i" Ii 


\  with  nans\  111        11: 
p.  St.     Oc,  (;  Ohj..?.) 


Plate  XXV. 


Fir;,  66.— Section  oi  an  injected  muscle  of  the  extremities  of  a  rat,  showing  the  distribution  of  blood-vessels  in  the 
transversely  striped  muscular  tissue,  a.  Arteriole,  b.  Vein.  d.  Capillary  between  them.  c.  Muscular  libre  with 
transverse  striae.    (Oc,  3;  Obj.,  5.) 

FIG.  68.— Isol  Oed  muscular  fibre  with  transverse  strias  from  an  oblique  section  of  the  tougue  of  a  frog  coloured 
with  chloride  of  gold.  The  muscle  cells  are  distinctly  shown,  and  three  are  visible,  each  containing  several  nuclei. 
p.  61.    (Oc,  3;  Obj.,  8.) 


'  "'  ""■   ,"'11  '"*•  Hue  of  a  cat,  macerated  In  bichromate  of  potash.    The 

nUataoce  of  the  cell   1   longitudinally  striated,  the  nuclei  ore  staff-shaped  and  well  defined,    p.  52.   (Oc.,3;  obj.,  7.) 


Plate  XXVI. 


PIG.  70.— Three  ganglion  cells  with  spiral  fibres  in  a  preparation  of  the  same  kind  as  fig.  69.     Each  ganglion 
cell  exhibits  a  nucleated  capsule,    p.  ?2.    (Oc,  4;  Obj.,  8.) 


FJC.  69.— Group  of  ganglion  cells  of  ■  a  me  trunk  of  the  urinary  bladder  of  a  rabbit,    Isolated 

a  coloured  in  gold  and  then  treated  with  dilute  acetic  acid.    p.  ja.    (Oc,  3;  Obi     -1 


Plate  XXVII. 


Fir;.    73.— Horizontal    section    of   cornea   of   rabbit    coloured    wit'i 
chloride    of    gold,    showing   the   superficial  intra-epithelial    i.etwork 
of  fine  non-medullated   nerve   fibres,  seen  from   the  surface. 
(Magnified  3oodiam.) 


PM   71  —Ganglion  ce't  bom  teasel  preparation  of  spinal  cord  of  olf,  mart-rated  in  bichromate  of  potash, 
i  11   cell   may  be  called  bipolar;  its  distinctly  flbrillated  structure,  and  tin-  large  nucleus  enclosed  in 

a  distinct  men, 1. ran.-,  with  its  large  nucleolus,  are  specially  to  be  noted,    p.  </,.    (Oc.,  3;  ObJ.,  8.) 

Horizontal  preparation  of  cornea  "f  rabbit  coloured  in  (raid,  showing  a  portion  of  the  sub-epithe- 
lial nerve-plexus,  with  a,  its  coarse  non-mednliated  nerve  trunks,  an  1  i,  sma'l  bundles  of  non-medollated 
nerve  fibres,    p.  7?.    (Oc,  3;  Obj.,  7  ) 


Plate  XXVIII. 


FIG.  72.— A  many-branched  ganglion  cell  from  the  same  preparation  as  fig.  71.  All  the  processes  are 
branched,  with  the  exception  of  a  tingle  pale  one— the  axis-cylinder  process,  which  is  also  distinguished  from 
the  others  by  its  more  delicate  lungitudinal  streaking,  and  the  absence  of  any  granular  substance  between  the 
stripes,    p.  69.    {Oc,  3;  Obj.,  8.) 


4  r- 


Ki'.   7 ,.  -Horizontal 

-■  -  propria     a.   Coai  e   oon-inedullated    uerve   trunk. 
Magnified  y>>  dlam.) 


.  blorldd   r,i    gold,  ihowing  ti 

b.    Fine    null-Jin  .liill.Ltcil    nerve   fibruH. 


if    the 


Plate  XXIX. 


-Horizontal  section  of  cornea  pi  rabbit  coloured  in  chloride  of  gold,  showing  a,  the  coarser  non- 
uiedullated  nerve  trunks  of  the  sub-epithelial  plexus;  b,  the  fine  non-medullated  nerve  fibres;  and  c,  tufts 
of  the  finest  nerve  fibrils,    p.  78.    (Magnified   i'jo  diain.) 


^C~ 


r 


W  \  '<u 


I  taerbach'i  pl^xuw  »>(  muU  Intestine  ><f  human   tetui   <-.,i<.ur<-<i  with  gold.     The   i 

idi  ap  '-f   trabecnUe   "f   ration*   thiol  m  11  ■   In    Largi    plncold 

Vaclena-lika  elementi  (unformed  ganglion  cell*)  and  ganglion  cell*  are  embedded  in  tin-  plexus,  the  whole oi 

Wbiefc  i-  frri<:l'.-.nj  in  a  nncleati  Oi      -■ ;  ObJ.,  7  i 


Plate  XXX. 


PIG.  79. — Horizontal  preparation  of  cornea  of  rabbit  coloured  with  chloride  of  gold,  a.  Larger,  b,  smaller 
non-medullated  nerve  fibres  ;  and  c,  the  smallest  fibrils  of  the  sub-epithelial  network,  p.  78.  (Oc„  3;  Obj.,  10. 
Immersion.) 


btaneblngi 
U*u»d  nerve 


Horizontal  lection  "f  cornea  oi  1  ired  in  chloride  <>f  gold,  sin  1  wing  the  BUb-epH  delial  nerve 

".  Coarse  non-medtiUated  nerve  trunk  oi  the  sub-epithelial  plexus,    b,  Fine,  and  c  finer  non-meduJ 
fibres  oi  the  subepithelial  ui  >diam.) 


Plate  XXXI. 


FIG.  8o.-Horizonta1  preparation  of  cornea  of  guineapig,  showing  the  superficial  intraepithelial  network  of  non 
medullated  nerve  fihres  as  seen  from  the  surface,    p.  78.    (Magnified  300  diam.  ;  reduced.) 


PlO.  81.— Horizontal  preparation  of  cornea  of  fro  I.  showing  the  dl  trih 

ihi  r  .i   port 1   'i uea.    a.  Com  e  non  medullated  111  rve  I 

■  order.    '■  and  c,  Non-tnedullated  oerre  fthrei  of  the  second  and  third  order,    p,  7  :-    (Oc,  1:  OhJ.,7.) 


FIG.  84. — Horizontal  preparation  of  the  same  kind  as  fig.  83.  showing  the  deepintra-epithelial  network  of  fine  non- 
medullated  nerve  fibres  viewed  from  the  surface,  a.  Contours  of  deepest  cells  of  anterior  epithelium,  b.  Nerve 
fibres,    p.  7       [Oc,  3;  01)]".,  7.    Tube  not  drawn  out.) 

Fig.  85.— Horizontal  section  of  cornea  of  rabbit  coloured  with  chloride  of  gold,  exhibiting  more  swellings  than  in 
fig.  73,  which  are  due  either  to  the  mode  of  preparation  or  to  the  appearance  of  foreshortened  nerve  fibres  passing 
upwards  or  downwards  into  other  layers.    (Oc.3;  Obj.,7.    Tube  half  drawn  out. } 


I  col hlorlde  of  gold,    a.  Large  non-medullated  nerve 

trunk",  im  ■  ""'     0.  Nerve  fibres  of  the  third  order.    I   cornea 

corpunelen.     p  8.) 


Plate  XXXIV. 


'*%r?P:'  f* 


FIG.  87.— Horizontal  preparation  of  nictitating  membrane  of  frog  in  chloride  of  gold,  showing  the  distribution  of 
non-inedullated  nerve  fibres  to,  a ,  capillary  blood-vessels.  6.  Coarse  non-medullated  nerve  fibres  giving  off  fine 
branches  c,  which  form  a  plexus  around  the  vessel,    p.  79.    (Oc,  3;  Obj.,  8.) 


ted  with  cbioridi  <<t  gold     a    Large  trunl  at  medullar  d  nam  abree,    b.  a  tingle 

.     \,,,i.,,,mii  belonging  to  the  mtmbrwna  propria 

of  the  u.enentery.    /.  Nucleus  of  fine  non-raedalUted  nerve  fibre     g.  Capillar]  bl <      P  (0o.,3;  ObJ.,8.) 


Plate  XXXV. 


FIG.  89.— Horizontal  prep  .ration  of  (lit  tail  of  the  tadpole  treated  with  chloride  of  gold.  a.  Capillary  blood-vessel. 
0.  Coarse  non-medullated  nerve  trunks,  a  Flnenon  medullated  nerve  fibres,  d.  Minute  fibrils  of  the  ultimate  sub- 
epithelial network,  in  which  cells  and  nuclei,  e,  are  scattered.  In  one  part  of  the  preparation  the  surface  epithelium 
is  left,  which  shows  the  relative  size  of  t!ie  meshes  of  the  sub-epithelial  network,  p.  80.  (Oc.,  3  ;  Obj.,  7.  Tube  not 
drawn  out.) 


Plate  XXXVI. 


PIG.  91.-  Horizontal  section  of  tongue  of  frog  treated 
with  chlorideof  gold,  showing  the  distribution  of  non- 
lnedullated  nerve  fibres  to  a  capillary  blood-vessel:  a. 
Capillary  vessel.  6.  Coarse  non-niedullated  nerve  fibres, 
c  and  d.  Fine  non-medullated  nerve  fibres  funning  a 
plexus  which  surrounds  the  vessel  like  a  sheath,  d. 
Non-inedullated  nerve  fibres  in  the  wall  of  the  vessel 
p.  83.     (Oc.,3;  Obj.,8.) 


PIO.  90.— Mesentery  of  frog  prepared  in  chloride  of 
bowing    the  distribution  of  non  medullated 
nerve  fibre*  t.»  h  capilli 

non-inedullated  nerve  Bbre  giving  <'ir  ftnei  branches, 
which  fonn  a  plexus  round  rb<-  capillary.    Borne  <>f- 


Flo.  92.— Tnwuverfte  Mction  of  mocouf  membnuieoi  vagina  "i  rabbit   pre] id  with 

the  plexuses  of  non-medullated  nei  ol  unstriped  muscular  fibre,  p. 

Obj.,  B.    Tube  not  drawp  oat  1 


Plate  XXXVII. 


FIG.  93. — Horizontal  preparation  of  the  base  of  a  gland  of  the  membrana  nictitans  of  the  frog  stained  with  chloride 
of  gold,  showing  the  distribution  of  non-med dilated  nerve  fibres  to  the  eland,  -a.  Membrana  /  roj  via  of  glan/I, 
6.  Coarse  non-medullated  nerve  trunk,  c.  Fine  non-medullated  nerve  fibres,  which  form  a  plexus  round  the  gland. 
From  these  fibres,  fine  fibrils  proceed,  which  penetrate  between  the  epithelial  cells,  d,  of  the  gland,    p.  79.    [Oc.,3; 

Obj.,8.) 


■      . 
Many  «f  thete  contain  nuclei 


utiofi  of  non-medul* 
. .  In     ..!,  two capillarii        Clrculai  mu  culai  flbn 
■    ■    1 1  ■  thi    in  terra  v     alar  1       11         Coara    non-medul- 

d.  Pine  t 

ObJ.,7.) 


Plate  XXXVIII. 


ntal  sect.:.  .11  of  mucous  membrane  of  vagina  of  rabbit  stained  with  chloride  <  :  . 
distribution  of  the  lion  med  tinted  nerves  under  the  surface  epithelium,    a.  Coarse  nerve  trunks     b.  0 
the  deepest  epithelial  cell  .    c.  Non-niedullated  nerve  fibres  forming  a  plexus     Ii  eta  maybe 

seen,  which,  leaving  tlie  di  identified  with  ti.e  interstitial  substance  of  the  deepc-t  epithelial  cells. 

Oc,  3:  Olij.,  8.     I  •■  ont  1 


1  irith  chloride  of  gold,  giving  U 
.   .  with  the  plexn  Bon-medallated  nerve  8  in  the  adventii 

m'lar  fibres  in   the  adveutltu  of  a  large  artery.    (Oc..  3 

oy.,7.) 


Plate  XXXIX. 


PIG.  07.— Horizontal  preparation  of  nictitating  membrane  uf  frog,  coloured  in  chlori<le<>£  gold;  showing  the-  distri- 
bution of  tlie  non-medullated  nerve  fibres  under  the  epithelium  of  the  posterior  surface,  a.  Larger,  6  smaller 
•  •  smallest  non-medullated  nerve  fibres,    p.  79.    (Oc,  3;  Obj.,  8.) 


mtlon  ol  the  bli 

layer.    '/    Medullar]  lajri  r.    ft  Largi  '"'  1     I 


Plate  XL. 


a 

FIG.  loo.— Transverse  section  of  an  artery  from  a 
vertical  section  of  the  skin  of  a  guineapig,  coloured 
with  gold.  a.  Lumen  of  ihe  vessel.  6.  Endothelium 
seen  in  profile,  c.  Intima.  d.  Circular  muscles, 
e.  Adventitia.  /.  Cellular  elements  of  adveutitia. 
p.  106.    (Oc.,3;  Obj.,  7.) 


PIG.  99.— Longitudinal  section  of  a  branch  of  the  pulmo- 
nary artery,  from  the  lung  of  a  guineapig,  the  bronchia;  of 

which  were  injected  with  dilute  chromic  acid.  a.  Intima. 
6.  Circular  layer  of  unstriped  muscular  fibres,  cut  across* 
c.  Adventitia.    p.  106.    (Oc,  3;  Obj.,  7.) 


FIG.  102.— A  capillary 
blood-vessel,  the  ca- 
vity of  which  is  extend- 
ing into  a  branched 
cell.    (Oc,  3     Obj.,  7.) 


Fin.  bu*— Preparation  from  tbe  normal  omentum  oj  a  rabbit,  fin  t  pencilled  and  then  treated  with  silver,  showing 

the  development  of  young  capillaries,    a.  Capillary  blood-vessels,    i>.  Capillaries  only  Just  hollowed  out;  this  pro* 

.1  the  branched  conned  Lve  tissue  cells,  d,  which  are  Ln  relation  with  the  capillary 

wail.    c.  Vacuoles  In  the  branched  cells.    0,  Branched  cells  of  the  ground    ubstanccC    f,  Migrator)  cells.    (Oc.,3 

obj..  7.) 


Plate  XLI. 


Flo.  103.— Omentum  of  rabbit  coloured  In  silver,  a.  One  of  the  larger  arteries,  shoving  the  spindle-shaped  endo- 
thelium and  transverse  muscular  fibre.  I>.  One  of  the  larger  veins,  showing  the  endothelial  elements,  which  are  not 
■o  elongated  a*  in  the  artery,    0.  Endothelium  of  one  oi  the  surfaces  of  the  membrane,    p.  105.    (Oc,  3    ObJ.,  5.) 


Plate  XLII. 


MO,  i<v4_— Part  of  the  name  preparation  as  tig.  103.    a.  Endothelium  of  one  of  the  surfaces,    b.  An  arteriole 
bnoohing  riesd,  which  are  continued  into  a  capillary  vein  c.    The  endothelium  ia  clearly  shown  in 

all  the  vensels.    (Oc,  3;  OhJ.,  7  1 


Plate  XLIII. 


F!<;.  105. — Vertical  section  of  mucosa  and  sul. mucosa 
of  injected  stomach  of  a  rat,  showing  the  rich  capillary 
system  of  the  mucosa  which  contains  the  peptic  glands. 
p.  126.    (Oc.,3;  Obj.,  2.) 


PIG.  107.— Horizontal  preparation  "f    mueona  inenibn I 

Injected  uterus  of   gnlni  1 ;|1    dense 

capillary meabwork, the  lb,  and  tin-  Mill  deepei 

[0  ■.,  3 ;  0I1J..2.) 


FIG.  106. — A  fat  tract  from  the  omentum 
of  an  injected  jiiii"  ii'iL'.  a.  Artery,  b. 
Vein.  r.  Denaeaysti  m  of  capillary  vessels 
of  true  fatty  tissue.    (Or.,  2  ;  OhJ.,  2.) 


Plate  XLIV. 


—Surface  preparation  of  the  mucous  membrane  of  the  stomach  of  a  rat,  injected  ;  showing  the  superficial 
arteries,  the  dense  network  of  capillaries,  and  the  deep  veins,  which  are  pale.    (Oc,  3  ;  Ohj.,  2.) 


WU.  loo.— Him*  of  tubercle  fwm  the  Injected  omeftt .fa  galneaplg,  artificially  infected  with  tub 

(chronic  inflammation   of   the  MrOUl   in. -ml/ran.  ...  Artery. 

b.  Vein.    Between  then  to  a  lieb  capillary  tyetem,  i  the  dumm  of  tnberela.   pp.  s8  and  115.    (Oc,  3 
ObJ.,  2.) 


Plate  XLV. 


Fir,,  no — Vertical  Bection  of  injected  tongue  of  rabbit,  showing  the  rich  system  of  vessels  with  which  the 
transversely  striped  muscular  substance  is  provided.    (Oc,  3;  Obj.,  2.) 


Plate  XLVI. 


FIG.  in.— Mesentery  of  frog  coloured  in  silver,  a.  Ordinary  surface  endothelium,  b.  Endothelial  cells  sur- 
rounding a  simple  true  stoma.  These  cells  have  the  germinating  character,  are  distinctly  granular,  and  are 
not  flat  like  those  which  surround  them.    p.  112.    (Oc,  3;  Obj.,  5.    Tube  not  drawn  out.) 


Fl';.  ii2.—S'j,tu.rn  cltterna    lymphatlca  magna  of  frog,  coloured  iu  silver.     A.   View  of  peritoneal   surface. 

B.  view  of  surface  of  lymph  s»c.    The  »tomat»,  »ome  of  irhli ih  ue  open,  ton lUp  ed,  are  surrounded  1  v 

IBIIllllnllllQ  endothelium,  which  is  ciliated  if  the  subject  is  a  female,    p.  112.    (Oc,  3;  ObJ.,  5.) 


Plate  XL VI I. 


Fig.  in.— Surface  view  01    mesentery,  coloured    in  silver,  of  :i  guineapig   affected   with   chronic  [nflam- 
,,i     : 1 1  i  1 1 1 . ■  i ; . ! [ -,    induced    tuberculoslB.      Proliferation    of    the    surface 

an  which   lurroaiida  ■•   •  rminatlng   endothelium.     «.  True  »t a,   open. 

the  endothelium   of    which  is  exposed  because  the  Btomata  belonging  to  them  are 
wide  open.    c.  Proliferating  endothelium,    d.  Ordimiry  surface  endothelium.    i>.  112.    (Oc,  3;  Obj.,  5.) 


Plate  XLVIII. 


*m 


FIG.  115.— Peritoneal  surface  of  centrum  tendineuin  of  rabbit,  treated  willi  water  and  then  coloured  in  silver. 
In  the  middle  of  the  preparation  a  lymph  vessel,  !,  appears  below  the  surface  endothelium,  i.e..  the  system 
of  lines  of  interstitial  substance.  On  both  sides  of  the  lymph  vessel  are  tendon  trabecular,  t.  The  endothe- 
lium which  coverd  the  lymph  channels  consists  of  smaller  elements.  Five  true  stomata  are  shown  which  pass 
through  the  "vertical  lymph  channels"  into  the  Ij'inph  vessel  below.  Two  of  the  stomata.  are  open,  and 
three  collapsed;  all  are  surrounded  by  germinating  endothelium,  p.  m.  (Oc,  3;  Obj.,  5.  Tube  not  drawn 
out.) 

ai c_ 


FIC.  114.— Similar  preparation,    c.  A  wide  lymph  vessel  which  can  be  seen  through  the  surface  endotheliums. 
An  artery,  d,  and  a  nervi  through  the  lymph  vessel  (perivascular  lymph  vessel)  c,   and    within 

the  field  of  vision   are  ten  distinctly  open  true  stomata  0.    The  surface  endothelium  bordering  the 
germinating,    p.  112,    (Oc,  3,   Obj.,  5.) 


Plate  XLIX. 


Via.  116.— Mesentery,  coloured  in  Bilver,  of  guineapig  affected  in  the  same  manner  as  in  fig.  113.  a.  Surface 
endothelium,  d.  The  freely  exposed  upper  wall  of  a  lymph  sinus,  the  endothelial  marking  of  which  is  seen. 
On  the  periphery,  however,  answering  to  the  free  surface  of  the  serous  membrane,  two  distinctly  open  true 
•  tomata,  6,  are  shown.  These  communicate  in  an  oblique  direction  with  the  lymph  sinus.  On  the  right  a 
closed  stoma  caa  be  seen.    The  endothelium,  c,  which  borders  the  stomata  is  in  germination.    (Oc,  3;  Obj.,  7.) 


Plate  L. 


Fig.  117. — Peritoneal  surface  of  centrum  tendineum  of  rabbit,  pencilled  and  coloured  in  silver,  showiDg  the 
lymph  capillaries  of  the  abdmi'nal  serous  covering  iu  the  neighbourhood  of  the  large  blood-vessels  which 
pas*  through  the  diaphragm.  The  sinuous  endothelium  of  the  lymph  capillaries  is  distinctly  bhown.  p.  114. 
Oe.,  3;  Obj.,  4.    Tube  halt  drawn  out.) 


PIO.  1  tH.— Pleural  surface  of  centrum  tendin'um  of  guineapig,  pencilled  and  coloured  in  silver.  A.  Lymph 
ve-seli  of  the  p'eural  side,  the  larger  trunks  having  iptDdU-lliaped  1  mi ■■llielium,  and  being  provided  with 
valve*.  Only  a  few  capillaries  are  to  be  seen — that  is  to  say,  few  vessels  with  sinuous  endothelium. 
B.  Principally  lymph  caplllaiies  which  run  between  the  tendinous  bundles,  p.  114.  (Oc,  3;  Obj.,  4.  Tube  not 
dmwu  out.) 


Plate  LI. 


9Va.  119.— Similar  preparation  of  ■  rabbit.  Bleb  netwoik  of  lymph  vessels  of  tlie  pleural  Bide.  a.  Large 
•  ranks  of  lymph  vessels,  having  spindle-shaped  endothelium  and  provided  with  va'ves.  h.  Lymph  capillaries, 
c.  Lymph  capillaries  which  penetrate  deeply,  i.e.,  which  bend  towards  the  abdominal  s.ile  in  order  to  run 
i>etwe«-u  the  bnndlM  of  tendon.    i>   m.    [Oc,  -;;  Ohj.,  2.) 


Plate  LI  I. 


1  ii.  ill.-il    iiinler  water  and  then   bathed    in    silver, 

while  an  1 1  u   m  being  carried   mi.     The   l.w,.,.  risible  in    the  Bllghtly-ioloured 

(found   ai  dutinet  and   very  ilnuoue  tabes,   the  endothelium   ..f    which   is  sharply   defined.     <i.  Trunks  of 
r/nrpo  reeseli  ol  b.  Lymph  capillaries  which,  ai  "strahjhl   Interfu  ciculu  lymph  .  . 

run  between  the  ten. Ion  ban  I  to  Um  abdominal  tide.    p.  [14.    (<>•  ,   :;  ObJ,,  5.) 


Plate   LIII. 


Pi'..  i2i.— Omentum    of    rabbit,    pencilled    anil    coloured    in    silver,      a.    ArLery.     b.    Capillary   Mood-vessel. 
<?.  Network  of  lymphatics,  recognized    a  lariee  )>y  tbeir  sinuous  endothelium  and  the  a 

Lymphatic  canalienll  oi  the  ground  ratmance;  in  most  of  them  the  nuclei  of  the  cells  contained 
in  them  are  se*-n.    p.  n>    (Oc,  ^;  ObJ.,  5.    Tube  ba'f  drawn  out.) 


Tr-ATE  LTV 


■Surface  of  omentum  of  rabbit,  pencilled  and  coloured  In  Hilver.  allowing   the  distribution  of  the 
lfin\i\t  jeuelB.    a.  Lymph  reaaeU,  •bowing  their  endotbellnm.    h.  Valve*,   c.  IuilicateK  the  position  of  vessels 
eiiel<«u-<l   iu  a  tra/.-t.   the  de'alll  "f   which,  an   well  as  th*>se  of  the  gr.mnd-sufoHtance  '/.  are  omitted.      p.    115. 
ObJ.,  51 


Plate  LV. 


Flo.  123.— Pleural  Bide  ef  pencilled  centrum  tendineam  of  n.  guiueapig,  in  which  there  was  chronic  inflain- 
matiult  of  the  serous  DUMIllUMIM,  in  eunse4tieaofl  of  artificially  iuduced  tuberculosis,  a.  Lymph  capillaries  of 
the  pleural  serosa  surrmndmx  an  island  of  $r jund-suhstance.  In  the  litter  is  the  canalii. ■  ilar  system,  with 
the  nucleated  flat  cells,  b,  which  it  contains.  These  cells,  in  var.ous  pla:es,  are  seen  to  lie  dividing;  and 
most  of  them  are  branched,  e.  The  Endothelium  of  the  lymph  capillaries  is  distinctly  seen  in  sevir.il  places 
Vj  he  in  continuity  with  the  cells  of  the  canalicular  system.    (Oc,  3;  Ohj.,  7.    Tu^e  not  drawn  out.) 


Plate  LVI. 


no.  124.— Pleural  side  of  centrum  tendineum  of  rabbit,  pencilled  and  coloured  in  silver.  I.  Lymph  capil- 
laries showing  their  endothelium.  The  system  of  lymphatic  canaliculi,  c,  stands  out  sharply  from  the  dark 
col  ,ured  ground-substance  of  the  pleural  serosa;  in  many  places  the  lacuna:  of  the  canalicular  system  are 
separated  from  each  other  by  mere  lines,  and  a  trace  of  nucleus  1  is  to  be  seen;  the  placoid  cell  to  which 
the  nucleus  belongs  is  not  visible.  At  r.  the  canalicular  system  is  passing  ovtr  into  endothelium  of  the 
lymph  capillaries,    p.  114.    (Oc,  3;  ObJ.,  7.    Tube  half  drawn  out.) 


Plate  LVII. 


<JN 


Fni.  125.— Similar   preparation    t<>   flg   124,    «.    Lymph   vessels   with  valves,   paining   over   Into  '<,  lymph 
cAp'lUrieti.    c.  Inlands  of  ground  nulieUnce  ihowing  the  canalicular  s)  stem,    p.  114,    (Oc,  3;  ObJ.,  5.) 


Plate  LVIII. 


FIG.  127.— Section  oi  cortical  layer  of  mesenteric  gland  of  ox,  which  has  been  hardened  in  Miiller'd  liquid 
and  then  shaken,  a.  Capillary  blood-vessel.  6.  Nucleated  cells  representing  the  nodes  of  the  delicate  reticulum 
—adenoid  tissue.    (Oc..  3;  Ohj..  7.) 


inentwn  ■>(    rabbit,  pencilled  and  coloured   In   silver,    a.  Lymphatic  capillary  in  the 

h  .<,.!  o(  u.  an  artery,    c.  Capillary  bl 1  vhii  h  la  evidently  to  continuity  with 

ti,'-    numerous    branched   eell   (arm  ,   d,   in   the  ground  thi   endothelium  ol  the  lymphatic 

capillary  U  •imilarl)  mtlnultjr  irltb.  thi  (Oc,  3;  ObJ.,  7.) 


Plate    LIX. 


_LkJ 


k 


fev         .1    fl  'Mfjjifg,','t'Jf 


FlO.  128.— Centrum  tendineutu  o!  rabbit,  Been  from  the  abdominal  side.  Berlin  blue  had  been  introduced  into 
the  peritoneaii]  by  "natural  injection."  f>.  Straight  interfascicular  Lymphatics  between  the  bundles  of  tendon 
of  the  abdominal  side.  a.  Lymph  vessels  of  the  pleural  side,  showing  the  valves,  with  corresponding  dila- 
tttioiM.      The  1; Lit  lymph  vessels  are  as  completely  injected  as  the  first.    (Oc,  3  ;  Obj.,  4.     Tube  not  drawn  out.) 


Plate  LX. 


-Section  "f  medullary  substance  of  n  ad  of   ox,  which  has  been   hardened  in   miller's 

liquid  and  then  partially  shaken.      Thi  the  lymphatic  cylinders   containing   bl 1-vessels,  sup 

rounded  b;    i  ed  lymph  corpuscles,  bfai    One]  .,i    cell      between 

tliem.    The  blank  i  the  trabecule  and  the  cylindei     repre  en<   the  Bystem  of  lymph  sinuses,  the 

lymph  corpuscles  ol  which  have  for  the  mostpArl   b  su    bakpn  out.    p,  117.    (Oc,  3;  Obj.,  8.    Tube  not  drawn 
out.) 


Plate  LXI. 


FIG.  130.— Alveolus  from  a  section  of  lung  of  rabbit,  frozen  and  coloured  in  silver,  a.  Inter  alveolar  septa 
of  elastic  fibres,  b.  Epithelium  of  the  alveolus,  seen  from  the  surface.  The  epithelial  cells  are  seen  edgewise 
on  the  borders  of  the  alveolus,    p.  120.    (Oc,  3;  Obj.,  7.) 


FIG.  132.— Section  of  a  lung  of  a  rabbit,  injected 
through  the  pulmonary  artery.  ".  Bfancn  "f  the 
pulmonary  artery'  losing  itself  in  h,  a  dense  capil- 
lary »y»teiu.    p.  120.    (Oj.,  3;  Obj.,  2.) 


Fig.  133.— Section  of  livr-r  ol  goineapig  harflfnH  In  bichromate  of  potash,  showing  tlie  cylindrical  trabecules 

■  Us.     The   spaces   between  tb>-   cylindrical  cell*  correspond  to  capillary  blood-vessels.    The    little 

opening*  b  n-tituent  cells  of  a  cylinder  are  capillary  bile  ducts  cut.across.    p.120.    (Oc.,  3;  Obj.,  8.) 


Plate  LXII. 


FIG.  134.— Horizontal  section  of  liver  of  dog,  the  vena  porta  of  which  has  been  injected,  a.  Trunk  of  inter- 
lobular vessel,  b.  Trunk  of  intralobular  vessel,  or  vena  centralis.  A  dense  system  of  capillary  vessels  is 
between  them.    p.  126.    (Oc,  3;  Obj.,  2.) 


Fin.  n?.— Vertical  lection  >.f  liver  of  1  1 1.  thi  portal  vein  and  hepatic  it  of  which  aro  injected,  a.  In- 
terlobular blood-veeeels.  t.  Interlobnlai  bile  d  1  network.  a  Intralobular  capillary  i>l<md-veasel«. 
a.    Intralobular   bill    1  ipl  larl        .     1  .  ■                     lei  "f  which  are  deeply  itained  with  carmine,    p.  126. 


Plate  LXIII. 


FIG.  136.— Vertical  section  of  injected  small  intestine  of  rat.  a.  Villus  showing  its  epithelium  and  dense 
system  of  capillary  vessels,  which  is  developed  from  a  central  artery  d,  and  terminates  in  two  peripheral 
veins,  •■.    b.  Mucosa,    c.  Portion  of  muscuZaru  externa,    p.  124.    (Oc,  2;  Obj.,  2.) 

FIG.  137.— Vertical  section  of  a  villus  of  the  small  intestine  of  a  cat,  hardened  id  chromic  acid.  a.  Streaked 
basal  border  of  epithelium,  b.  Cylindrical  epithelium,  c.  Goblet  cells,  d.  Central  lymph  vessel,  e.  Smooth 
muscular  fibres  which  lie  nearest  to  the  lymph  vessels.  /.  Adenoid  struma  of  the  villas  in  which  lymph 
corpuscles  lie.    p.  124.    {Oc,  3;  Obj.,  8.) 


.1    iiiif.inii  papilla  ol    tongue  "f   rabbit,     a.    Epithelial    covering  ol   papilla?. 
b.  Capillar;  loop  ol  papilla,    e.  Ve    ell  ol  the  mucosa,     d.  Vessels  of  longitudinal  muscles,    p.  122.    (Oc,  2; 

Obj.,   .:   . 

1  1  .    :     .,  ■  >   large  bronchus   ol  human  Castas,   bom  b  Lung  hardened    In   chromic   acid. 

cylindrical   epithelium  in   layers.    '«.  Uueosa.    0.  Bundles  '.1    onstrlped   muscular  fibre,     d.  Sub- 

■1  -int.  showing  Portion     i  cartilaginous   ring,     /.  <m  the  left,  an 

•  through ;  on  the  right,  below,  »  »eln.    g.  Trnnks  "f  inedullated  oerve  liiire  out  through,    h.  Section 

•il  ganglion,    p.  1        10  Obj.,  4.    Tubs  not  drawn  out.) 

1   a*  rigs.  157  and 


Plate  LXIV. 


Fig.  140.— Two  injected  follicles  from  transverse  section  of  Fever's  patches  of  small  intestine  of  rabbit.  Out 
of  the  plexus  of  large  vessels  which  surrounds  the  follicle,  numerous  capillaries  are  developed,  which  tend 
towards  the  centre  of  the  follicle,  and  for  the  most  part  turn  hack  so  as  to  form  loops,  p.  125.  (Oc,  3 
Obj.,  2.) 


/ 


T  .''  '•     r.'^'p, !'/?(fP\ '., %/   ..,.-    •;'■      ,   >i   ;v.  ; 


Y\<:.  141.— Vertical  lectl >t  portion  ..f  Uenm  "f   dog,  baidaned  bj  chromic  acid.     «.  Villus,  showing  its 

cylindrical  epithelium  with  tbicli  basal  border.     The     troma  at  the  villus  Menu  to  I  oiely-paetod 

lymph  oorpusclas;  botwi  at  onstriped  muscular  ftbre.     '-.  Mucosa  with  Lleoerkohnlan  crypts. 

I  Ich  the  nimmil    ol  the  follicles,  ■/.  project,  bo  order  to 

reach  the  epithelium  oi  U  .;■,.,   ...     ,,/ „„.,,,    ,,  which  the  follicle    are  olomly  packed, 

>  as  to  form  a  Payer'    patch      lit  th.   baas  of  tl Hides  the  lymph  sinuses,  «, 

mmnd  them  010  i«  seen.   /.  Portion  of  circular  muscular  layer  of  the  muicuiurit  vxurna.   p.  izf. 

Oc,  3;   Obj.,  x) 


Plate  LXV. 


Fig.  143.— From  a  longitudinal  section  of  the  injected  kidney  of  a  rat.  a.  Arterial  trunk,  i.  Venous 
trunk,  c.  Glomerulus,  d.  Vas  afferens  of  the  glomerulus,  e.  Vas  efferens.  /.  Capillaries  which  twine  round 
the  convoluted  tubes,    g.  Capillary  vessels  of  the  pj-raniidal  processes,    p.  134.    (Oc,  3;  Obj.,  4.) 


FKi.  142—  Section,  parallel  with  the  surface,  at  an  acinus  at  the  same  preparation  as  fig.  735.  a.  Into* 
lobular  aipfUary  blood-veueL  b.  intralobular  capillary  bile  duet  c  Liver  cells,  p.  126.  (Oc.,3;  Obj.,  7.)  (.see 
aluo  fig.  135.) 

Fi<;.  i44.~Froni  a  kidney  of  pig  Injected  from  the  ureter,  ihawtng  Che  arrangement  •  ■!  the  tul*f  in  the 
pyramidal  anbitaace,    a   Collecting  tubei    t    Henb/a  loope,    p.  134-    t(>c,  3;  obj.,  2.) 


Plate   LXVI. 


1  I  ■■    ■   I      ■'   tl ted  kidney  of  a  rat,     Li   I  aw   mu  the  bundla    at 

■    the  pyramid*,    B.  Cortical    ubatance,    p    i,      (Oo.,   i;  Ob].,  a.) 


Plate  LXYII. 


Fig.  146  —Transverse  section  of  pyramidal  substance  of  kidney  of  pig,  the  blood-vessels  of  which  are  injected. 
a.  Large  collecting  tube,  cut  across,  lined  with  cylindrical  epithelium,  b.  Branch  of  collecting  tube,  cut 
across,  lined  with  epithelium  with  shorter  cylinders,  c  and  d,  Henle's  loops  cut  across,  e.  Blood-vessels  cut 
across.    D.  Connective  tissue  ground-substance,    p.  132. 

FIG.  147.— Teased  preparation  from  a  section  of  kidney  of  pig,  hardened  in  bichromate  of  potash,  showing  a 
HenW'a  loop.    a.  Membrana  propria,    b.  Epithelium. 


PIO.  i4''— The  a  portion  of  a  collecting  tube  m  the  pyramidal  px sees  of  the  corttcolU.     \ 

ahowi  the  lumen  '•>'  the  tube;  '',  the  membrana  propria;  «.  the  cylindrical  epithelium,    p.  132.    (oc,  3.) 

FlO.  149.— Section  of  cortical   substance  of    kidney  of    human    foetus,   hardened   in    bi.hr ate  of  potash. 

«.  Glomerului  with  lb)  IU  membruna  propria, ;  and  c,  the  epithelium  of  polyhedric  ci  1;  covering  the  glome- 
1.  d,  thi  ii.ii.-n.-d  epithelium  which  Uee  upon  the  inner  surface  of 
the  Bowm  /•  Convoluted  urinary  tube  ou(       ro         1     1  12.    ISru  also  fig.  155.) 


Plate  XLVIII. 


FIG.  iis— Peritoneal  surface  of  centrum  tendineuin  of  rabbit,  treated  wilh  water  and  then  coloured  in  silver. 
In  the  middle  of  the  preparation  a  lymph  vessel,  J,  appears  below  the  surface  endothelium,  i.e.,  the  system 
of  lines  of  interstitial  substance.  On  both  sides  of  the  lymph  vessel  are  tendon  trabecular,  t.  The  endothe- 
lium which  covers  the  lymph  channels  consists  of  smaller  elements.  Five  true  stomata  are  shown  which  pass 
through  the  "vertical  lymph  channels"  into  the  lymph  vessel  below.  Two  of  the  stomata  are  open,  and 
three  collapsed;  all  are  surrounded  by  germinating  endothelium,  p.  ill.  (Oc,  3;  Obj.,  5.  Tube  not  drawn 
out.) 

a c_ 


Fr<..  114.— Similar  preparation,    c.  A  wide  lymph  vessel  which  can  be  seen  through  the  surf:*'  1  ad 
An  artery,  d.  and  a  nerve  trunk,  e,  pan  through  the  lymph  vessel  (perivascular  lymph  renal)  c,   and    within 
the  field  of  vi»iou   are  ten  distinctly  open  true  stomata  b.    The  Burface  endothelium  bordering  the    (ton  kta  ll 
germ  mating,    p.  112,    (Oc,  3,  Obj.,  5.) 


•Plate  LXIX. 


j£52E£i'7t£: 


FIG.  153. — Tabular  glands  of  human  prostata,  hardened  in  chromic  acid,  showing  the  cylindrical  epithelium 
which  covers  them.    p.  137. 

FIG.  154.— Section  of  cortical  substance  of  kidney  of  six  months'  human  foetus,  hardened  in  bichromate  of 
potash,  a.  Glomerulus,  b.  Membrana  propria,  which  extends  over  the  glomerulus,  and  which  is  a  direct 
continuation  of  Bowman's  capsule.  At  the  point  of  section  it  appears  as  if  it  consisted  of  spindle-shaped 
elements  placed  together,  c.  The  epithelium  of  cylindrical  elements  which  covers  the  glomerulus,  d.  Epithe- 
lium -.f  polyhedral  cells  which  lines  Bowman's  capsule.  /.  Convoluted  urinary  tube  cut  through  transversely. 
p.   132.     {See  also  fig.   14).) 


1  section  "f  human  eyelid,  showing  the  tabular  glands  which  are  embedded  In  that  part 
bos,  which  la  i  I  Dioxide  of  gold  preparation,  har- 

dened in  alcohol,    a.  Conn  rich  in  branched  cells,  In  which  the  tubular  glands  (£) 

are  embedded.    These  are  shown  cat  through  in  rarloui  direction       We       bi        •  rselv,  as  at  <■,  it 

is  seen  that  the  epithelium  oorering  them  consists  of  cylindrical  nucleated  cells,    (OoM  3;  OhJ.i  **.) 


Plate  LXX. 


FIG.  156.— Vertical  section  of  cornea  of  rabbit,  hardened  in  chromic  acid.  a.  Anterior  layer  of  pavement 
epithelium,  b.  Substantia  propria  of  the  cornea,  consisting  of  connective  tissue  fibres  in  more  or  less  parallel 
bundles,  between  which  are  the  cornea  corpuscles.  These,  in  vertical  sections,  appear  spindle  shaped,  c.  The 
posterior  lamina  elastics ,  or  Descemet's  membrane,  and  the  endothelium  of  polyhedral  cells,  d  which  covers 
it.    p.  13K. 


WW' 


FIG.   157. — Diagram  of    the  connective 
substance  of  the  retina. 


FIG.  158. — Diagram  of  the  nervous  ele- 
ments of  the  retina  (after  Max  Schultze), 
These  two  diagrams  must  be  supposed  to 
fit  into  one  another  in  such  a  way  that 
the  nervous  elements  fill  corresponding 
spaces  in  the  connective  substance.  In 
157,  the  lower  line  represents  the  limitans 
interna ;  the  line  8  the  Umilant  externa, 
2.  Layer  of  nerve  fibres.  3.  Layer  of 
ganglion  cells.  4.  Inner  finely  granular, 
or,  more  correctly,  finely  ribrillated  layer 
which  really  Conns  an  extremely  close 
network  01  very  tine  fibres  int<j  which, 
on  the  one  hand,  the  processes,  of  the 
ganglion  cells  penetrate;  out  of  which, 
on  the  other  hand,  the  fibres  of  the  inner 
granular  layer,  s.  proceed.  The  outer 
processes  of    the  elements  of  this    layer 

similarly    terminate    in    a    cl 

fibrillar    network,   6,    the     intermediate 
granular  layer  or  outer  flnelj 
or,  iii.,1-.;  correctly,  finely  fibi  Ulai 
Out  of  this   proceed   the  Inner  1 
of  the  outer  granular  layer,  7,  which  ter- 
minate as  rods  and  cones,  9.    p.  142. 


Plate  LXXI. 


-  -163.— Various  stages  of  cleavage  of  the  egg  of   the  trout,    a.  Germ.    6.  Section  of  yolk  ou  which 
the  germ  lies.    p.  148.    (These  figures  are  referred  to  in  the  text,  by  error,  as  146-150.) 


FIG.  164.— Germ  iu  an  early  stage  of  cleavage, 
<i.  Vitelline  membrane.     6.  Germ.    c.  Yolk. 


Flo.  165.— Vertical  section  of  blastoderm  of  the  egg  of  a  trout 
at  the  third  day.  a.  Germ,  already  split  into  a  large  number  of 
elements,  in  some  of  which  the  dark  yolk  granules  can  be  dis- 
tinctly recognized,    6.  Yolk  of  the  saucer-shaped  depression,  filled 


Wwk 


made  at  the  sixth  day.    The  blastoderm,  whirl the  jrolk  like  a  cushion, 

consists,  a  li         1    ■     '<'•<  element  .    The  deeper  elemento,  those  not  ao 

Ur  adraiu 


Plate  LXXII. 


FIG.  167.— Similar  preparation  at  the  twelfth  day.  The  blastoderm  has  increased  considerably  in  width,  and 
shows  at  a  a  marginal  thickening.  Opposite  the  thinner  central  portion,  d,  the  blastoderm  is  separated  from 
the  yolk,  e,  by  a  hollow  space,  the  cleavage  cavity,  b.  It  is  still,  however,  connected  with  the  yolk  by 
columns  of  cells,  the  sub-germinal  processes. 


n 


% 
B     !£'"£  "3    it 


ggssag      //, 


no.  i'/,  172.— Sections  of   the  egg  of   bnfo  cinereus,  intended  relations  between   the  cleavage 

cavity   and    Bnaeoni's   cavity,   eventually    the  viscera]    cavity  (after   Strieker).     B.  The   dorsal   aspect  of 

B.  The  vejitral  aspect.    I  N.  In   169.  and  170,   Etusconi's  cleft;  in  ■  ;.,  Knsooni's  cavity 

:-.  Dome  of  the  <vage,  and 

original  upper  pole  ol   U  Oi                                                                      dally  In  171 

and  I-L-.  Bcker'e  yolk   ping.    2.  1  ...:.  of  the  cleai                     centra]  yolk    mi 

larger,  that  la,  less  ad  than  the  elements  in  the  dome   "f  the  cleavage 

cavity  or  of  *U  making  their  way  alon                        rface  of  the  oovi 

the  nppei  pole.    They  answer  to  the  formative  elements  of  the  tront'a  i-xx.    Rusconi's 

cleft  adrai  "  171.  where  the  olefl  has  become  :i  cavity,  they  an.-  separated 

by  a  layer  "I   I  •  ,it».  1.    in  172,  owing  to  tin-  alteration  in  its  centre  of 

the  egg  has  Chan                           th.-  white  pole  being  now  nearly  uppermost,    p.  152. 


Plate  LXXIII. 


FIG.  168.— Vertical  section  oJ  peripheral  part  of  blastoderm  of  trout's  egg  at  the  fourteenth  day.  6.  Margina 
thickening,  c.  Central  thin  portion  of  blastoderm,  showing  superficially  a  layer  of  flattened  elements,  under 
which  is  a  layer  of  spheroidal  elements,  ,t.  The  blastoderm  rests  on  the  yolk  by  means  of  the  sub-germinal 
processes,  as  in  fig.  167.  The  formative  elements,  e,  on  the  floor  of  the  cleavage  cavity,  a,  are  derived  from 
the  blastoderm;  either  from  the  sub-germinal  processes,  or  from  the  lower  layer,  d,  of  the  central  portion. 
f.  Yolk  of  the  saucer-shaped  depression,    g.  Vacuoles  (fat  globules?). 


Flo.  173.— Vertical  lection  of   the  dona]  furrow  oi   th  dnereui.     </.  Cornea 

layer,    b.  Donal  furrow,    c.   Commencing  central   uervi  Perl 

liberal  portion  of  nervous  layer.    /.  Peripheral    p  9    1 lb   "i- 

epithelial  glandular  layer,     h.   Buwsoni's  cavity.     11.    1  !  central   yolk  mass.     k.  The  re- 
mainder oi  the  cleavage  cavity,     p.  153. 


Plate  LXXIV 


FIG.  174. — Section  of  the  cover  or  dome  of  Euaconi's  cavity  (Bufo).  a.  Corneal  layer.  b.  Nervous 
layer,  c.  Motor-genniuative  layer,  d.  Epithelial  glandular  layer,  c  and  d  are  the  offspring  of  formative 
elements. 


FIG.  175.— Vertical  section  of  a  portion  of  the  area  peUucida  and  area  opaca  of  the  blastoderm  of  a  fresh- 
laid  hen's  egg.  In  the  section  corresponding  to  the  area  peUucida,  the  blastoderm  consists  of  two  distinct 
layers,  a  the  upper,  and  6  the  lower;  the  latter  looser  and  consisting  of  larger  elements,  cc.  Formativ 
elemeuts  lying  on  the  floor  of  the  cleavage  cavity  F,  which  have  originated  from  the  germ,  and  are  filled  with 
yolk  granules.    These  elements  are  continuous  with  similar  ones  in  the  area  opaca. 


—Section  of  blastoderm  of  hen's  egg,  at  the  fifteenth  hour  of  incubation,  a.  T'pier,  and  i  lower 
ayer.  c.  Cleavage  cavity.  </.  Toll  rim.  /.  Formative  elements  on  the  floor  of  the  cleavage  cavity,  g.  Similar 
elements  which  have  already  migrated  in  between  the  layers  of  the  blastoderm. 


WUk  177.   flection  of  comment  I   the  twenty-aixtfa  hour  after  Incubation     a.   I  ppi  r.  0  middle, 

c  under  Uyer.    '/.  Central  portion  of  the  middle  layer,  vrbica  itli  Um  upper  layer.    *-.  Primitive 

groo\  e.     1 


Plate  LXXV. 


Fig.  178. — Similar  preparation  at  the  thirty-sixth  hour.  a.  Upper  layer,  b.  Parietal  lamella,  lamina  ven~ 
tmlis  [ffautontukelpUUte).  c.  Lamina  serosa,  visceral  lamella  [Darntfaserpiatte),  d.  Lower  layer.  /.  Central 
nervous  system,  g.  Chorda  dorsalis.  h.  Proto-vertebne.  ;".  Wollfian  body.  ft.  Pleuro-peritoneal  fissure.  0,  c, 
k,  i,  g,  are  products  of  differentiation  of  the  middle  layer,    p.  156. 


Fig.  179.— Section  of  area  opaca,  and  a  portion  of  area  pettucida  of  blastoderm  (caudal  end),  at  the  thirtieth 
hour.  Ap.  Area  peUucida.  Ao.  Area  opaca.  b.  Upper,  c  under.  M  middle  layer  of  germ,  <■.  Lamina  ven- 
trolls,  d.  Lamina  serosa,  f.  Uluud-vessels.  g.  Elements  which  belong  to  the  middle  layer,  and  particularly  to 
the  lamina  serosa,    h.  Yolk  of  the  inner  yolk  rim. 


1  j  n        srtlou  through  the  cervical  pa]  ......  <.f  the  chicle  eth  hour  <>f 

"    1  ppex  layer  oi  th<     era     6   Central   doti ■■  tern     c.  C) — la  dorsalU      d    Pi'oto'vertebraj, 

c.  Lamina  oentraUs,   /  Lamina  terosa.    a.  Lower  layer. 


Plate  LXXYI. 


Fig.  181.— Section  of  embryo  of   chick  at  the  beginning  <>£    the  second  day,   in  the   neighbourhood  of  the 

heart,    a.  Upper  or  corneal   layer.     '>.    Centra]   Canal   of    the   central  nervous   system,    d.   Under  or  epithelial 

glandular  layer.    D.  Anterior  intestine  (Vorderdann),  e.  Lamina  serosa,  f.  Lamina  ventralis.  g.  Aort:e.  *.  rente 

m.    Fold  of   amnios.    //.    Pleuro-peritoneal  cavity,     h.    Heart   cavity,    h.    Endothelium  of   wall  of 

heart,    e'.  Proper  wall  of  heart.    /;.  Bluud  corpuscles. 


MS 


—Transition  of  the  tin  i  bhi  fcod indothelial  n   Iclee  containing  blood 

enons  development  of    bl I  corpuscles),    i.   Coarsely  granular  formative  element  in   which 

l*.,iai'-d  fin-  lei,  a,  are  found.  a  f ew  bl  od   corpnscli   ,  a,  are  distinguishable,  while  b 

peripheral  zone,  i  rest  ol  the  cell.    In  }.  the  peripheral  ileated   layer 

[i  i   mi  [rely   <>\    coloured 

d    ..  '.•   Icle  lined  with  endothelium  and  filled  with  bl I  corpusoles, 

II  uely    granular    protoplasm,   With    Its    more   or    less    regularly   arran   ed    I 

endothelium  of  a  I 


Plate  LXXVII. 


—Section  of  the  posterior  part  of  the  body  of  the  embryo  of  the  chick  at  the  forty-eighth  hour. 
«.  Central  nervous  system,  b.  Proto-vertebrae.  c.  Chorda  dorsalU.  d.  Upper  or  corneal  layer,  e.  Serous,  and/, 
ventral  lamina,  g.  Wollfian  duct.  h.  AorUe.  i.  Pleuro-peritoneal  cavity,  k.  Lower  layer.  D.  Intestinal 
furrow,    a.  Amniotic  fold.    !.  Bl.iod  vessels. 


n  of  anterior  ■  -.      ■  inlddli    •  >!"   the  pecond  day.     a.  Cavity  of 

//.   Wui!  of   cerebral  reticle,     c.  Primary  optic  :•■  lole,  and   d   tta  wall.    e.   Upper 

layer  of  :■                         olng  of  the  opp  r.  Middle  lsyei     /«.  :.Tnu 
optical.     ! 


Plate  LXXVIII. 


FIGS.  184-186.— Various  stages  in  the  transition  of  the  primary  into  the  secondary  optic  vesicle,  and  the 
development  of  the  lens  at  the  end  of  the  second  and  during  the  third  day. 

186.  a.  Cavity  of  secondary  optic  vesicle,  b.  Rudiment  of  retina,  c.  Rudiment  of  pigment  epithelium  of  the 
choroid,    d.  Nermu  opticus,    e.  Lens.    /.  Upper  or  corneal  layer. 

184.  a.  Primary  optic  vesicle,  and  6  its  wall.  c.  Ncrnis  opticus,  d.  Upper  or  corneal  layer,  e.  Beginning  of 
lens. 

185.  a.  Primary  optic  vesicle.  6.  Saucer  shaped  cavity,  which  subsequently  becomes  the  secondary  optic 
vesicle,  c.  Xervus  opticus,  d.  Outer  wall,  and  e  inner  wall,  of  primary  optic  vesicle,  f.  Upper  or  corneal  layer. 
g.  Rudiment  of  lens. 


FIG.  188.— Other  forms  of  elements,  in  which   blood    corpuscles  arc  produced,    a,  a,  are  the   cavities  of  vesi- 
cular structure*,  produced  by  the  formation  of  vacuoles,  in  originally  solid  cells.     The  wall  of  the  vesicle  6, 
!   11  (top]     '"    1   pre  Bnts  the  endothelium  of  the  future  vessel,  for  whirl,  reason  these 
vesicles  may  1*  called  endothelial  vesicles.    At,/,   blood   oorpuscles  arc  detaching  themselves  from  Die  inner 
portion  of  a  vesicli  m  element  at  another  kind,  in   which  blood  corpuscles  are   formed.    It  is  a 

spindle-shaped  m  d  e,i],  the  central  portion  of  which  becomes  hluud  corpuscles,  and  the    peri- 

pheral portion  endothelium.  bat  in  rig.  187. 

i    formative   elemente   Ol    M I  10   communication    with    each    other  by 

■olid  oflkboots.    They  have   this  in   common,    that  io  jUI  a  peripheral  layer  of  nucleated  protoplasm  is  dif- 
iterior,  which  contains  s  number  of  blood  corpuscles.    The  interiors  of 

neighbouring  elements  eventually  be, ,.,,,1,   each  other   by  tie    oris] 1.   oi    communicating 

threads  above  mentioned,  which  becomi  hollowed  out,  and  thus  give  rise  to  a  system  of  tubes,  the  blood-vessels. 


Plate  LXXIX. 


HO.  190.— Test  tube,  with  foot,  used  for  subsidence  of  small  quantities  of  blood  (§  1). 

WO.  •  [tin  plate  for  collecting  blood  and  keeping  it  at  OOC  |§  2). 

WO.  lOx-Coagulatlon  of  blood  of  frog  Id  ■  fine  capillary  tube,     ffartnack.    (Ob].  0;  immersion.    Oc.  3.) 

-a.  Oammla  Cot  Bchafert  experiment,    i  shows  the  form  into  which  a  tube  is  drawn  rat  for  the 

d  of  an  arterial  cannula  (§  9);  the  tube  is  first  severed  at  one  of  ti utrlctions,  and  then  filed 

away  m  the  direction  of  the  oblique  line.    c.  T-shaped  arterial  cannula;  the  horizontal  tube  is  in  communica- 
tion with  the  manometer  of  the  kymograph  (§  33). 

I  tor  studying   the   action  of  induction  shock!    on    blood.    The  drop  of  blood  to  I va- 

in.n.-d  U  placed  between   the   tinfoil  pointa  on  the  under  surface  of  the  fixed  square  cover  glass.     The  chamber 
i»  closed  by  placing  a  second  ordinary  object-glass  below  it  (§  13). 


Plate  LXXX. 


FIG.  196.  —  Hoppe-Seyler's  bottle  for  preiraring 
fibrin  (§  23). 

FIG.  195.— Various  absorption  spectra.  1.  o'4  per 
cent,  solution  of  haemoglobin.  2.  Reduced  haemo- 
globin (§  18).  3.  Hrematoin  (§  22).  4.  Reduced  htematin 
(§  21).  5-  °'°6  per  cent,  solution  of  hfeinoglobiu. 
6.  07  per  cent,  solution  of  the  same  (§  24). 


;-.-.--;-'  v. 


F10.  198.— Ueissler's  mercurial  pump  |?  27) 


li'..  I-..?.— Alvergniai'i  minimal  pump 


Plate  LXXXI. 


Fro.  199.— FiantlanJ-Sprengel  pump  (5 


Fig.  201— '<  ud  b.  tfeedlM  Cm  pairing  UfCri  .  ,..  Urilcke's  blunt  liwk.    d.  Tre- 

liljii,':     e.  Curved  needle.    /.  Cured  and  11..1 


Plate  LXXXII. 


FIG.  aco.— FrHiiklaud's  api>aratuB  for  the  analysis  oi  gases  by  absorption  (|  30).    [From  Button's  Volum.  Analysis.) 


Plate  LXXXIII. 


F"^ 


Fl«.  204. — Czeruiak's  rabbit  support  (§  34). 


FIG.  201.— Frankland  and  Ward's  apparatus  for  explosion  <§  v)-    (From  Button's  Volum.  Analysis.) 


Plate  LXXXIV. 


PIG.  20Z.— The  mercurial  kymograph,  a.  Vulcanite  rod  of  floating  pistou.  b.  Tube  which  conummicates 
with  the  pressure  bottle,  c.  Tube  wliich  communicates  with  the  artery,  d.  Feeding  cylinder,  i.  First  axis, 
which  revolves  once  in  a  minute.  2.  Second  axis,  which  revolves  once  in  ten  seconds.  3.  Third  axis,  in  a 
second  and  a  half  (§  33).  The  instrument  is  furnished  with  other  cylinders  suitable  for  the  reception  of 
single  liands  of  glaztd  paper,  the  surface  of  which  can  be  blackened  after  they  are  fixed  on  to  the  cylinders, 
by  causing  the  latter  to  revolve  over  the  flame  of  a  petroleum  lamp.  These  cylinders  can  be  fitted  ou  to 
either  of  the  axes  1.  2,  or  3,  and  are  always  used  when  it  is  necessary  to  employ  a  rapidly-moving  surface, 
ui,  *'..'/.,  for  tracing  the  curves  of  muscular  contraction. 


Yu..  206.— Normal  tracing  of  arterial  pressure  obtained  with  the  mercurial  kymograph  (rabbit). 


Plate  LXXXV. 


FIG.  205. — Pick's  spring  kymograph.  A.  C -spring,  bb.  Suppo 
of  the  spring  to  the  lever  1),  and  thus  to  the  writing-needle  1 
spring  is  in  communication  with  the  artery. 


C.  Rod  which  communicates  the  movements 
K.  Leaden  tube  by  which  the  cavity  of  the 


Firr.  207 


Ficr  207a 


Fl'i.  207.—  Normal  arterial  tracing  obtained  with  the  spring  kymograph  (dog  under  curare). 

1'i'..  -.;■/.— Tracing  of  Bame  animal  after  exhaustion  of  vagus  by  repeated  excitations;  dicrotoua  pulse. 


Via,  206.— Meohanical  arrangement  of  the  sphygmograph  {§ 


Plate  LXXXVI. 


Fig   209.— End  view  of  the  block  by  which  the  sphygiuograph  rests  on  the  bones  of  the  wrist,  showing  the 
screw.   G,  by   which  the  pressure  exercised  by  the  spring  on  the  artery  can  be  varied  (§  39). 
FIG.  2096.— Breguet's  improvement  |§  39). 
PIG    2io. — Mode  of  measuring  pressure  (§  39). 


PIQ.  211.— Schema  f  r  demonstrating  the  nature  of  the  arterial  movements.  A.  Glass  tube  which  represents 
the  heart.  B.  The  tul.e  by  which  A  communicates  with  a  cistern  at  a  height  of  ten  or  twelve  feet  above  it.  (A. 
much  smaller  head  of  water  is  sufficient.)  C.  The  lever  by  which  the  two  valves  K  and  L>  are  worked,  the 
same  act  which  shuts  the  one  opening  tin-  other.  1'.  Oommenceinent  of  the  experimental  tube,  which  is  of 
black  vulcanite.  At  9  the  tut.e  communicates  with  a  long  vertical  tube  of  glass,  only  part  of  which  is  seen; 
It  is  closed  at  the  top,  and  usually  shut  off  from  K  t>y  a  pinohcock.  At  (l  tin?  tube  passes  under  the  spring  of 
the  sphygmograph,  the  frame  of  which  rests  on  a  block  (below  t<).  By  error,  the  tube  has  bean  drawn  on  the 
wrong  side  of  the  block,  II.  The  blackened  plate  of  the  iphygmograph.  To  the  left  of  it  is  seen  the  cylin- 
der, with  its  needle  for  recording  the  time  which  intervenes  between  the  opening  ami  closing  of  the  aortic 
valve,  D.  I..  A  rod  which  is  lirmly  fixed  in  the  lever,  and  is  connected  by  two  cords,  ono  of  which  is  elastic 
with    the  cylinder  1$  40). 


Plate  LXXXVII. 


-Tracings  obtained  with  the  arterial  schema  (§  40). 


FIG.  2126.— Natural  pulse. 


FIG.  213.— Percussion  waves  (§  41.) 

rami:* 


Fin.  2U.— Tracings  showing  the  contractions  and  expansions  of  an  india-rubber  tulle,  along  which  water  is 
propelled  in  an  intermitting  stream  hy  squeezing  with  the  hand  at  regular  intervals  of  time  an  elastic  bag 
provided  with  valves,  with  which  the  tube  is  in  communication;  the  bag  thus  represents  the  heart.  The  three 
tracings  are  drawn  simultaneously,  and  exhibit  the  expansive  movements  of  the  tube  at  three  different  dis- 
tanees  from  the  bog;,  the  upper  tracing  being  taken  at  the  greatest  distance  (§  41). 


Fn;.  21C  — Dr.  OMon'i  (Uh-trongb  i«  |4l.     It  1   be  naed  with  the  mlaraoope  itage  Inclined  ■)  an  ingle  ..f 

kbonl  i   . 


Plate  LXXXYIII 


FIG.  ar;.— Stage  for  mesentery  of  frofi  {§  44). 


Fig.  218.— Cannulas  for  aorta  and  vena  cava  of  frog. 
The  right-hand  figure  represents  the  arterial  cannula. 
They  are  of  size  suitable  for  large  specimens  of  It. 
eteulenta  (§  46). 


PIO.  219.— Diagram  of  arrangement  for  measuring 
objects  seen  under  the  microscope,  a.  Axis  of  tube 
at  microscope,  t.  Pri  in,  tj.  Direction  in  which  the 
object  \>  '     board,  which  should 

be  at  a    1  utimeters]  from  the 

eye.    The  angle*  of  tbi   |  1  ial,   the  angle 

($  48). 


31.— Griffin's  bl  ae  used  fox  gas  blow-pipe.     The  blower  la  used  (or  artificial 

respiration  (tee  i  vi). 


,  ■,.,!..  liquid  into 


Plate  LXXXIX. 


FIG.  224.— Skull  of  rabbit  seen  from  behind,  p  p.  Parietal 
bones  ;  i,  interparietal  bone  ;  below  i,  occipital  tubercle  ;  above 
P,  occipital  protuberance.  Half-way  between  the  tubercle  and 
the  protuberance  is  the  point  at  which  the  bone  must  be  per- 
forated in  the  operation  for  producing  glycosuria  (§  50). 


Fir;.  222—  Bprengel'i  blower  (5  49). 

Fir;.  225.— Exettor.     The  wires  are  of  oopper,  with  platinum  print!.     Their  sheaths  aro  made  of  bits  of  flexible 
catheu-r.  ami  are  bound  together  with  raxed  »ilk  (§  51). 

1   in  the  rabbit  by  an   in.  1  Ion    extending  from  the  thyroid  cartilage  to  the  root  of 
Bifurcation  '.r  tin-  |ugulai    rein;    /</".•,  poeterioi   buriaJ  vein;    p a »,  poeterloi  anrloular 

vein;    a/r,  anterior  (acta]  vein  ;    num..  great  ;■ ni.n  nerve,  where  it  emerge!  at    the   posterior  edge  of 

1  mtucle  (}  w). 


FIG.  227.— Carutid  artiry  of  rabbit,  and  parte  m  relation  with  it.  c,  Carotid; 
c  ?»,  cornti  m  ijus  hi  hyoid  bom  ;  8  ft,  stylohyoid  muscle;  ft,  hypoglossal  nerve; 
f,  sympathetic;  v,  vagus  nerve;  i.  points  to  superior  laryngeal  nerve  where, 
close  to  its  origin  from  the  vagus,  it  passes  behind  the  carotid  ;  p,  pharyngeal 
artery;  f  m,  edge  of  sterno-inastoid  muscle;  t  ft,  thyroid  artery;  s  I  ft,  sterno- 
hyoid muscle  ;  I,  laryngeal  artery  the  nerve  which  crosses  it  is  the  descendem 
noni  (§  56). 


I  c  1 

PIG.  22a— Heart   of    froj    (aftel    Frittche);  front   vien    t..   the  left,  back  \i 

the  right.      .1  .1.  Anrt.e  ;     v.r.*.,    vena   earns  tuperioret ;   At.t,  left  auricle; 

ri^ht  auricle  ;  fen.,  ventricle;  li.m-..  Bulbut  arteriosus:  8.V.,  sin  113  venosue;  I'.c.i. 

Inferior  ;  v.h.,  vena  hepatica  :  V.p.,  vena  pulmonale!  (§  57). 


It.i/, 
rena 


in.              '                apanam  and   lei             Beu  ug     in   H  liich  th<  ' 

be  rained  or  depressed  at  «iii,  by  means  of  the  little  adju  tin      level    th« 
backwards  and  slightly  downwards   b  opal /,  tube 


;       1,1      II, 1      I.      1 

long  arm   of  which    i 

bj    \\  lii'-li  its    cavity  c 


ude. 


ith   the   cardiograph;    thii  tube  enters  the  tyn  paiiuin    by  a    horizontal    metal  tul u    Its  further 


Plate  XCI. 


I            .                                           'i  ■!>,/■.  na    caw 

■  Simula  in  wi                                    Hon  with  the   manometer;    i  tub      uarded   bj 

clip,  by  which  proximal  end  "I   manonu                                   rte,  which   record  the  distal 

column  »l  Hi'-  iiiaii./iiK-i'T  on  'In:  cylinder;    n.   heart;    K,    ligature,  by  irhlch  the  tnbe  la  eeoured  tu   the 

>i« ;    I.,  bolder,  by  «  bich  the  ulan*  red  J  Is  supported  (S  63).    , 


Plate  XCII. 


■■■ill 


llll 


llll 

llll 
llll 


attain 

!ll        kill 

■■■■■■  H»l 


FIG.  237. — Dissection  of  the  parts  in  relation  with 
the  vagus  nerve  of  the  frog  on  the  right  side.  The 
oesophagus  is  distended  with  a  glass  tube  about  half 
an  inch  in  width.  The  object  is  represented  of  about 
twice  the  actual  size,  a.  Right  aorta  ;  B,  bitlbus 
aortCB ;  c,  posterior  horn  of  hyoid  bone  ;  g.h.,  genio- 
hyoid muscle  ;  h.g.,  hyoglossus  muscle  ;  p,  lowest  of  the 
three  petrohyoid  muscles;  H,  ninth  nerve;  G,  glosso- 
pharyngeal nerve;  r,  vagus  ;  6,  larynx  ;  s&h&  oh.,  point 
to  the  space  occupied  by  the  origins  of  the  large  muscle 
(sternohyoid)  which  connects  the  hyoid  with  the  ster- 
num, as  well  as  by  the  omohyoid  ;  both  of  these  muscles 
have  been  cut  away  (§  73). 


-Tracings  obtained  by  recording  simultaneously  on  the  same  cylinder  the  variations  of  pressure  in 

the  right  auricle,  right 
ventricle,  and  left  ven- 
tricle, respectively.  The 
interval  between  each 
vertical  line  and  the 
next  corresponds  to 
about  a  tenth  of  a  se- 
cond. The  second  ver- 
tical line  is  just  before 
the  completion  of  the 
systole  of  the  auricles. 
The  contraction  of  the 
ventricles  falls  be* 
tween  the  third  and 
fourth  lines.  It  ends 
between  the  seventh 
and  eighth  ;  conse- 
quently, in  the  horse, 
the  interval  of  time 
between  the  auricular 
systole  and  that  of 
the  ventricles  is  about 
o'iS  sec,  and  the 
duration  of  the  ventri- 
cular systole  is  about 
o"4  sec.  (After  Chau- 
veau  ;  see  §  67.) 


FIG.  236.  —  Septum 
auricularum  of  frog,  a, 
Muscular  fibres ;  6,  endo- 
cardium ;  c,  free  edge  of 
septum ;  dd,  wall  of  ven- 
tricle; e,  right  cardiac 
brooch  of  vagus  ;  /,  left 
branch;  h,  anterior 
nerve  of  upturn ;  *', 
posterior  nerve;  kkt 
Didder's  ganglia;  //, 
ganglia  of  ventricle; 
§  69.  {After  Bidder,) 


Plate  XCIII. 


FIG.  240.— Sketch  to  illustrate  the  relations  of  the 
ganglionic  cord  in  the  visceral  cavity  of  the  frog. 
The  septum  citlemce  magna  having  been  divided  on 
the  right  side,  the  right  kidney  is  turned  over  towards 
the  left,  so  as  to  expose  the  parts  concealed  by  it,  viz., 
the  aorta  and  the  ganglionic  cord  of  the  same  side. 
The  stomach  and  the  first  coil  of  intestine  are  also 
turned  over,  so  that  the  posterior  surface  of  the 
former  organ  is  presented.  In  this  way  the  origin  of 
the  mesenteric  artery  from  the  junction  of  the  right 
and  left  aorta?  is  brought  into  view.  On  its  surface 
nervous  filameuts,  which  spi-ing  from  the  ganglionic 
Cord,  may  1*  traced.  These  [nerri  metenterici)  com- 
bine to  form  a  plexus  with  similar  filaments  from 
•he  corresponding  ganglion  of  the  other  side.  (.See  fig. 
295.)    I,  Liver;  rl,  right  lung;  »,  stomach;  *,  kidney. 

Fir..  241.— Heart,  lungs,  and  gTeat  vessels  of  the  rabbit, 
with  the  nerves  In  relation  willi  thrni.  (After  Ludw ig, 
■lightly  altered.)  V.c.d.,  v.c.t..  Kit-lit  and  left  venaeemt 
tuperiortt ;the  li  represented  as  if  cut 

away,  in  order  to  Show  the  m-rv.  '  <  ...  .  „  •  ervicate 
inf.riiin  j  m,  sympathetic ;  i>.  vagus;  d,  depressor.  The 
dotted  Unas  on  each   side  indict  p         "  of  the 

(I  81). 

1  .Dissection  of  the  lower  cervical  ganglion  hi  tin-  .log.  and  of  the  parts  in  relation  with   it.   (Alter 

Behmledeh  mimon  trunk  of  the  ^agus  and  sympathetic ;    fcphrenici  «l 

■       ■  •  rlorcei  deal  ganglion  (6) 

B,  flr-t    I.  rale  ganglion;  0,  ratntw  cardiac. h  mptrtor ;  11,  trunk   of 
',  it). 


Plate  XCIV. 


FIG.  244. — Tracing  (after  Schuiiedeberg)  showing  the  effect  of  electrical  stimulation  of  tlie  vagus  of  a  frog  under 
the  influence  of  nicotin.  The  line  ending  in  asterisks  indicates  the  duration  of  the  period  of  excitation 
1$  81). 


FIG.  243.— Dissection  of  in- 
ferior cervical  ganglion  of 
rabbit.  The  pectoral  mus- 
cles and  sterno-clavicular 
ligament  have  been  divided, 
and  other  more  superficial 
parts  removed.  The  dotted 
line  indicates  the  middle  line 
of  the  body,  g  I,  A  lym- 
phatic gland  in  contact  with 
the  apex  of  the  lung  ;  a  x, 
sub-claviau  artery  ;  a  v,  ver- 
tebral artery  ;  v,  vagus  nerve  ; 
*,  sympathetic  ;  pt  phrenic 
(§  81J. 

FIG.  246.— Respiratory  mus- 
cles of  frog  (after  Ecker). 
smt,  submental  is ;  g  h,  ge- 
niohyoideus  ;  h  g,  hyo- 
glOBBUB  ;    k  m.  submaxillaris  ; 

*  m",  anterior  horn  of  the 
hyoid  hone ;  p  k,  petrohy- 
oidei ;       oh,      omohyoidens; 

*  h,  sternohyoideus. 


FIG.  247.— Recording  Stethometer. 
A.Tynipanuin  ;  B,  ivory  knob;  B'rod 
which  carries  the  knob  opposed  to 
B.  C,  T-tube,  by  which  A  communi- 
catee, on  the  one  hand  with  the  re* 
cording  tympanum,  on  the  otherwith 
an  elastic  bag  D.  The  purpose  of  the 
Twg  is  to  enable  the  observer  to  vary 
tlie  quantity  of  air  in  the  cavity  of 
the  tympana  at  will.  The  tube  lead* 
i tiK  ("  K  [1  closed  by  a  clip  when  the 
Instrument  u  in  nee.   ($  Pq). 


tlatk  xcv. 


Fig.  250.— Boxwood  Pulley  for  recording  the  movements  of  a  needle,  Inserted  in  the  diaphragii 
is  attached  to  the  horizontal  arm  {§  91). 

Fit:.  251. — Rosenthal's  apparatus,  with  W.  MU11er*8  valves  l§  <&>. 


txmlc  bu  td  i';is  itj  96), 


Plate  XCVI. 


no.  257.— The  lever  kymograph,  fur  recording  the  respiratory  and  arterial  movements  simultaneously  (§  105). 


PIG.  as&— Tracing  trbtalnad  with  the  tov«  kymograph  1$  105), 


Flate  XCYII. 


FIG.  265.— The  calorimeter  ({  116). 


ultlpller,  for  thermo-electric  currents  (J  119). 

Fl,.    ...  „  (ram  ■  on  which  i>»-  wire  It  colled 

! 


EXPLANATION  OF  PLATES  XCYIII.  TO  CI. 


FIG.  229.— Tracing  drawn  by  a  lever  applied  directly  to  the  apex   of  the  heart  of  the  frog. 

Fig,  2^4.— Tracing  of  endocardial  pressure  of  heart  of  frog,  obtained  by  Coats'  method. 

Fins.  238a  and ©. — Synchronous  tracings  of  arterial  pressure,  and  respiratory  movement  of  air  in  trachea, 
taken  (a)  immediately  before,  and  (M  one  minute  after,  section  of  both  vagi.  The  lever  kymograph  (fig.  257) 
was  employed.  Arterial  pressure  before  section  about  igo  m.iu.,  after  suction  about  [80  in  in.  Pulse  rate 
before  section  no,  after  section  260.  Respirations  before  section  24,  after  section  10.  The  characteristic  violence 
of  the  expiratory  movements  after  section  is  well  shown. 

FIG.  239.—  a.  Tracing  of  arterial  pressure  of  rabbit,  obtained  with  Fick's  kymograph  (fig.  205)  during 
excitation  of  peripheral  end  of  divided  vagus,  with  feeble  induced  currents  (secondary  coil  far  removed 
from  primary).  Duration  of  excitation  of  nerve  indicated  by  asterisks,  b.  The  same,  with  secondary  coil 
brought  nearer. 

Flii.  245.— Traeiug  of  arterial  pressure  with  Fick's  kymograph  during  excitation  of  the  central  end  of  the 
depressor  nerve  (§  82). 

FIG.  233.-11.  Tracing  obtained  with  the  cardiograph,  when  the  button  is  applied  to  the  seat  of  impulse  of 
the  human  heart,  b.  Tracing  obtained  when  the  button  is  applied  either  outside  of  the  impulse  or  nearer  the 
sternum.  The  line  of  sudden  descent  in  b  coincides  with  that  of  sudden  ascent  in  a.  Both  are  coincident 
with  the  sudden  hardening  of  the  ventricle,  i.e.,  with  the  complete  closure  of  the  mitral  and  tricuspid 
valves  (§  60). 

FIG.  246  bis.— Tracing  of  respiration  of  frog  {§  86). 

FIG.  249.— Tracing  of  intrathoracic   pressure  (§  90). 

FIG.  248. — Tracing  obtained  with  the  stethometer  when  applied  as  in  fig.  247.  i.  Inspiration  ;  e,  expiration. 
Immediately  after  n,  a  notch  in  each  of  the  curves  occurs,  the  descending  limb  of  which  expresses  the 
moment  of  cardiac  impulse.     Compare  fig.  2326  {§  89). 

FiG.  253.— Respiration  of  the  cat  before  and  after  section  of  both  vagi.  The  tracing  expresses  the  variations 
of  pressure  which  occur  in  the  air  passages  during  each  respiratory  act.  In  b  the  horizontal  Hue  is  that 
drawn  by  the  lever  when  at  rest  ;  consequently,  when  the  pressure  in  the  air  passages  is  less  than  that  of 
the  atmosphere  the  lever  rises,  when  it  is  greater  it  falls.  The  sudden  expiratory  movement  which  is  the 
most  marked  characteristic  of  the  mode  of  breathing  after  section  of  both  nerves  commences  at  e.   (§  92). 

FIG.  263a. — Tracing  of  arterial  pressure  and  respiratory  movements  in  the  second  stage  of  asphyxia  by  OCCluslon, 
a  p.  Arterial  pressure  ;  i,  respiration.     Both  tracings  express  the  movements  of  mercurial  manometers  (S  109). 

FIG.  2636.— Slow  asphyxia.  The  lower  tracing  expresses  the  movements  of  an  elastic  bag  in  communication 
with  the  trachea  (§  no), 

FIGS.  259-261.— Tracings  of  respiratory  movements  of  the  dog  before  and  after  CUrarization  (j  105), 

FIG.  262.— Tracings  of  artificial  respiration  and  arterial  pressure,  showing  Traube's  curves,  as  seen  with  vagi 
intact    (§  106). 

Fit:.  264.— Effect  of  a  single  injection  of  air  in  a  curaiized  dog,  after  long  discontinuance  of  artificial  respiration 
(§  in). 

FIGS.  2^4  and  255.— Excitation  of  the  central  end  of  the  vagus  in  the  rabbit  (§§  102  and  103). 

FIG.  256.— Excitation  of  the  central  end  of  the  superior  Laryngeal  nerve  (§  194). 


\Plate  98.        Ficr.  229 


Fi£.238.« 


Fig-.  232  6 


Plate /OQ. 


Fior.259. 


S\l\f~ 


itafr-resji 


Fig.  260 


Fig. 261 


a^aaaaa/       ^aaaaaat     ^^vvvvw^^Aaj^ 


arf.resjo 


Fig.  262, 


Fig. 264. 


\art.ye.yj. 


Plate  CI  I. 


266.— Diagram  of  a  frog,  to  show  the  lines  of  incision  necessary  in  various  orxervati  ins. 


FIG.  267. — Diagram  of  the  uraa- 
he  leg  of  a  frog,  pi 

ma   femoris  ;     6, 
in.-r.s;  e,    seiei  a 

■■  coocygeo-iliacn  ;  1  /. 
tendo  achillii  1  g,  gastrocne- 
mius ;  h.  bead  ol  gastrocnemins  : 

•us  (the  muscle  also 
marked  £  in  front  <-f  and  partly 
hidden  by  the  preceding  is  the 
tibialis  1     ins  In- 

ternal ;   ">.    glntarai ;   ».    pyri- 

;  a.   ilium  ;  ./', 

The    ni  1 1 
.0      l  ,   end    "f    lemur  ; 
nerve  :  1.  tendo  aohlllla; 
f.  attachment  "i  ■mailer  tend  in 
Ixocnemlni  to  femur. 


Plate  CIII. 


FIG.  Myographion  of  Pfliiger. 

The  moist  chamber,  which  is  sup- 
ported by  the  large  pillar,  and  from 
Which  the  thread  h  descends,  is  nut 
shown.  The  lever  "  moves  freely  on 
the  t«o  pillars  bb.  At /the  rod  6, 
bearing  the  movable  style  </,  with 
lis  movable  c  ainterpoise  ;j,  swings 
easily.  At  the  opposite  end  of  the 
lever  is  theheavy  counterpoise  c.  The 
milled  head  on  the  side  of  one  of  the 
pillars  b  rotates  the  lower  of  the 
two  bars  connecting  b  and  b.  A  silk 
thread  is  carried  from  -•  to  thi.s  bar. 
By  turning  the  milled  head  the  style 
may  thus  he  allowed  to  fall  upon  or 
remove  away  from  the  recording 
surface  as  desired 


I    G  —The  moist 

chamber,  with  the 
uezi  e-muscle  prepar- 
ation, non-pularizaMe 
electrodes,  electrode- 
bearer,  and  lever  in 
position  ready  for 
an  observation.  Tin: 
glass  cover  is  not 
shown. 


FI<;.  270  bis.  —  Simph 
spring  myograph  of  M.-ire'* 
arranged  horizontally 

(See  ch.  xix.) 


Plate  CIV. 


FIG.  271. — Ordinary  electrodes.    The  pair  011  the  right  band  being  the  pail  spoken  of  in  the  text  as  curved  and 
shielded. 

FIG.  272.— A  non-polarizable  electrode  in  the  bearer. 


FIG.  :;;.— Ends  of  non-polarizable  electrodes.  A,  with  the  clay  plug  6  projecting  beyond  the  glass  tube;  B,  with 
the  end  "f  the  glass  tube  closed  and  bent,  a  hole  being  drilled  in  the  tube  at  b',  to  expose  the  ping  ;  C,  oblique  end 
with  the  clay  plug  flush  with  the  glass  tube. 

FIG.  274. — Kronecker's  1 


rf  apparatus  for  «tudyiii  '  ' '■■  *■  *• 

1)  the  polarizing  1  by  thee mutator  1   with  the  two  celled 

>\    fed  '  "'   ""   ' ",,l",v  "■'l  "■ 

'  .  Ills  pri 


Plate  CV. 


PIG.  277.— The  recording  tuning  fork. 


<**$.l. 


FlG.  278.— 
Diagram  of 
the  muscles  of 
the  thigh  of  a 
frog,  anterior 
surface.  $,  gar* 
torius ;  ad.m., 
adductor  mag- 
nus ;  r.i.,  rec- 
tus    intemus 


FIG.  23o.—  Muscle  iu  a  trough  bearing  two  levers,  in  order 
to  show  the  wave  of    muscular  contraction.     To    the  left 
are   seen  the  pointed  electrodes  and  the  clamp  fastening  the  muscle.     At  the  other  end  uf  the 
thread  connected  with  the  lever. 


Fig.  23i.— A  different  disposition  of  the 
levers,  intended  to  show  the  same  thing. 
The  levers  seen  below  the  platform  on  to 
which  the  muscle  is  fastened,  are  connected 
with  slips  which  pass  round  the  muscle 
at  different  parts  of  its  length. 


FIG.  279.  —  Dia- 
gram oi  a  muscle 
curve  asdrawn  on  a 
travelling  surface. 
c,the  line  described 
by  the  point  of  the 
lever  connected 
with  tho  muscle ; 
11 ,  the  Line  described 
by  marking  lever; 

■ id 

by  the  tuning- 
fork.  The  verticil 
Line  "'  marks  the 
m  uuenl  - 1  stlmu- 
Latlon,  m'  the  he- 
ginning,  ma  the 
tin,  and  m  \ 
tl I     of      the 

on  of  tba 


Plate  CVI. 


Fig.  282.— Diagram  of  the  curve  of  teta- 
nus. 4,  the  Hue  drawn  by  the  point  of 
the  lever  connected  with  the  muscle ;  o. 
the  liue  of  the  marking  lever.  The  record- 
ing surface  is  supposed  to  be  moving 
slowly.  The  line  m  marks  the  commence- 
ment of  stimulation,  and  also  of  the  con- 
traction (the  movement  not  being  suffi- 
ciently rapid  to  show  the  latent  period); 
mi,  the  cessation  of  stimulation  and  the 
commencement  of  relaxation ;  m3,  the 
return  of  the  muscle  to  its  former  length. 
The  straight  line,  which  is  the  continua- 
tion of  4  from  m  to  m3,  is  the  line 
which  would  have  been  described  by  the 
muscle  in  the  absence  of  all  contraction. 


FIG.  283. — Lower  part  of  large  figure. 
Curve  of  tetanus,  showing  the  individual 
contractions.  Below  are  seen  the  vibra- 
tions of  a  recording  tuning-fork. 


FIG.  284.— Upper  part  of  large  figure. 
Curves  illustrating  the  increased  extensi- 
bility of  a  muscle  during  tetanus. 


Fig.  285.— MnselM  and  uervea  at  bog, 
mi  m  1  tor  the  Mcperlmant  of  the 
"  rheoaooplc  frog." 


Plate  CVII. 


Thomson's  galvanometer  and  scale, 

FIG.  287.— The  shunt 
of  the  galvanometer. 

FIG.      a88.— Diagram 

illustrating  the  "natu- 
ral "  current  in  a  piece 
61  muscle.  The  equator 
is  marked  by  the  posi- 
tive sign,  and  the  mid- 
points of  the  transverse 
sections  by  the  negative. 
The  arrows  denote  the 
direct. on  of  the  current 
through  the  galvano- 
meter. The  larger  curves 
denotethe  stronger  cur- 
rents, and  lice  versd. 
aa,  are  two  points  on  the  longitudinal  surface  equidistant  from  the 
equator  ;    between  them,  therefore,  there  is  no  current. 


(2 


®rf 


ZB 


/; 


1  11  \  1  rani '"  "'  ■ ' '  ""  ' ,"'1'"  l'';l,'l,' '  lectrode  iliu   1  q  be»i 

ration  of  the  natural  current*  In  a  uerve, 

Via.  -.■■:■       0  igi  ",,  Ulu  I  rati '■  I  rotonu      p  »,  thi  polai  Iziai     1  I 

,,     /./,..  1,  1 1 1     0  placed  .-is  i"  »ho«  the  eft  < 1    ■    • al '  on 

...  .,, al  I  ol  •'• n    ■  l>ea   the  arizing  current  is  in 

n  ..1  Hi.' 1     hi  iin   i' .  the  "■ 1   ■  " I  "i    n 

11  I-  iin  p    I-.'.,  hil-ii,  while  Hi."  of  I  'i 

■    Ign. 


Plate  CVITI. 


FIG.  291.— Diagram  of  a  muscle  ami  nerves,  arranged  to 
show  the  use  of  the  eleetrotonic  change  in  "lie  nerve.  A,  as 
a  stimulus  for  another,  B.  I.  II.  two  different  modes  ol 
placing  the  nerve  of  A  on  I! ;  III.  the  so-called  "  para- 
doxical contraction." 

FIG.  292.— Apparatus  for  showing  the  effects  of  varying  temperatures  on  a  muse] 


FIG    233.— The  induction  aopsratus  of  Do  Bois  Eeymond,  with  the  magnetic  interrupter. 


Via  '    me  of  above 


Plate  CIX. 


/Mi 


— Diagraujof  the  nervous  system  of  a  frog— anterior  (or  Inferior)  v  iiw.     i,  :•,  3,  *,&,  I"  [0,  Cranial  nerves 

in    order.    7a,  ophthalm  palatine  nerve;    Ye,  luperlor  maxillary;    Vd,  inferior  maxillary j  Ft 

tympanic  nerve,  which,  after  Joining  withtheromi  q  form/*,  the  facial  serve* 

•  '.7.  ganglia  I  1     1.  branohea  of  teuthpalri  ,ting  branch  with  tympanic  nerve;  X2 

I    :,  nerves  '■■  rtomaoli  and  lute  tlna  ;  1  1.  on  X  '-',  ganglionof  vagus 

Jf,  spinal  cord:  mpathetli      in  lla,  nninbered  a rdlng  to  the 

ritb  which  tbey  communicate;  A' c,  crural  1  joker,  slightly  altered.) 

!  1  frog  from  above,  enlarged.    Col,  olfai  rebral  hemlBphara 

(;./,.  pineal  body  ;    /'■*<  oplie  thalaml  \  /..•>/>.  optic  lobe*;  ft  oerabeUum  ;  If.o.  Medulla  oblongata ; fl.rft.  sinus 
rhoroboidaUa. 
i 


Plate  CX. 


Fin.  298.— The  Rbeochord.  The  diagram  represents  the  end  of  the  board  on  which  the  resistance  wires  are 
stretched,  a,  b,  c.  d,  e,f,  g,  are  brass  blocks  which  would,  if  it  were  not  for  the  wires,  be  insulated.  From  the 
block  b  a  german  silver  wire  (the  course  of  which  is  indicated  by  the  dotted  line},  after  turning  round  an  ivory  pin 
at  1,  returns  to  c.  From  c  a  similar  wire  of  exactly  the  same  length  returns  to  d.  From  d  a  wire  three  times  the 
length  returns  to  e ;  e  and /are  connected  by  a  wire  five  times  as  long.  From  each  of  the  blocks  a  and  6  platinum 
wires  extend  to  the  further  end  of  the  board,  a  distance  of  more  than  a  metre,  which  are  insulated  at  their 
extremities.  They  are,  however,  in  metallic  connection  by  means  of  a  slide  ("  travelling  mercury  cups  ")  shown  in 
the  diagram.  According  to  the  distance  of  the  slide  from  a  and  6,  which  can  be  measured  by  a  scale  ontheboard, 
the  resistance  between  a  and  b  can  be  varied.  "When  the  slide  is  as  far  as  it  will  go,  the  resistance  is  equal  to  that 
between  6  and  c,  or  c  and  d.  Wheu  the  slide  is  pushed  up  to  a  b,  the  total  resistance  of  the  rheochord  is  twenty 
times  as  great  as  between  6  a«d  c.  If  plugs  {not  shown  in  the  dagram)  are  inserted  between  each  block  and  its 
neighbour,  the  resistance  is  nil.    (See  p.  347.) 

FIG.  299.— Double  key. 


FIG.  300.— I>'i  Boll  Kryi.i'.n.]'.  k>  y. 


Plate  CXI. 


W 


FIG.  301.— Creatine. 


FIG.  302. — Creatinine. 


FIG.  303.— Nitrate  of  hypoxanthine. 


:  — Hyilr'K.lilxnttc  '.f    xanthine. 


FIG.  305.— I  til  ! 


Plate  CXII. 


FIG.  306.— P,  potato  starch  ;  W,  wheat  starch  ;  R,  rice  starch;  A,  arrowroot'  starch. 


Fh;.  307. — After  Bernard.  Nerves  of  the  submaxillary  and  sublingual  glands  of  the  dog.  N.  Submaxillary 
Gland.  O.  Sublingual  gland.  .1  M.  Wharton's  duct,  in  which  a  cannula  has  been  placed.  J  L.  Duct  of  the  sub- 
lingual gland,  also  furnished  with  a  cannula.  T,  s,  s'.  The  lingual  branch  of  the  fifth  nerve.  F.  The  facial  nerve. 
c.  Chorda  tynipani.  g.  The  submaxillary  ganglion,  q.  The  superior  cervical  ganglion.  P.  Sympathetic  twig 
passing  from  the  ganglion  to 'the  submaxillary  gland,  j.  Internal  maxillary  artery.  V.  Vidian  nerve.  (.Branch 
of  the  lingual  nerve  ramifying  in  the  breccal  mucous  membrane. 


1     Paint  at  the  submaxillary  gland.   11.  Submaxillary  gland,  J.  Jugular  \  <  in,  dividing 

,/aud/',  which  pan  along  the  l«. mi.  1      "l  ill.'   gland,     1/.   Anterior  vein,  and    •'     DOlt v. in. 

bDSB  Qm  gland. 


Tlate  CXIII 


*■"•    •'  ■■'  Ountmt  -t  the  rabnuxillaiy  gland  in  the  dog    <■■  Bnfamaxlllan 

gland,  from  irhicl  >  k,  accompanied  al  fliel  by  the  total*  of  .]„■  mblingual  (land,  which  farther  on 

"'       '      '         t.   Ungual  :irt-ry.     0.  Artery  of  tli-  gland,     It   »].ni.K*  ir..ni  the 

In  from  the  acta  IB",    The  bypogloeia]  nerve,  .  „i  ecroai  to  upon  the 

superior  cervical  gang i  which  Ilea  beneath  It    (r.  The  vagus,    p.  A  evinpathetlc  filament,  which  li  oonneoted 

ganglion,  ami  j.,in»  the  ragna  town  down.    i>.  Branch  ol  the  flrai  oer 
lug  with  the  superior  cervical  ganglion,    it  it.  Glossopharyngeal  nerve,    i.  Anterior  branch!     ol  the 
sopertora  tomiing the inter-carotid plexna which  imal  oarotld  artery,    p.  A 

■mall  sympathetic  twin  which  aacendi  to  the  iabma»lllary gland,  a ipauylngal  Bid  the  Inferior  artery  O.and 

indular  aitarjr  !•'.   ■/.  BympaUu  „>,,„.  ,i„.  fata]  artery  and 

wnnlngni  I  tta  mylohyoid  branch,  of  the  fifth,    a.  Thi  Ungu posterior  atpect ol 

1,1  d  to  Hi-  glaud  forming  anaatot 

filaments  of  the  «ym|*thetlc    t.  Bxternal  division  ol  the  spinel  acceseory  nerve. 


Plate  CXIV. 


FIG.  310.—  After  Bernard.  Anatomy  of  the  parts  exposed  in  operations  on  the  submaxillary  gland.  The  pos- 
terior half  of  the  digastric  muscle  has  been  removed.  M.  Anterior  half  of  the  muscle  drawn  aside  by  a  hook. 
M  .  Insertion  of  the  posterior  half,  which  has  been  removed  in  order  to  expose  the  carotid  artery,  t  V.  Sympathetic 
filaments.  G.  Submaxillary  gland  drawn  aside  by  a  hook  in  order  to  show  its  deep  surface.  H.  Submaxillary 
and  sublingual  ducts.  J.  Trunk  of  the  external  jugular  vein.  J'.  Branch  of  the  jugular  vein  passing  behind  the 
gland.  J".  Branch  of  the  jugular  vein  passing  in  front  of  the  gland,  cut  across.  D.  A  vein  issuing  from  the  sub- 
maxillary gland.  1 1'.  Carotid  artery  accompanied  by  a  sympathetic  filament  on  either  side  ;  only  one  filament,  f, 
>s  distinctly  shown  in  the  engraving.  F.  Origin  of  the  inferior  artery  of  the  gland.  P.  Hypoglossal  nerve. 
L.  Lingual  nerve.  T.  Chorda  ty  11  ipani  going  to  the  submaxillary  gland.  S  S'.  Mylo-hyoid  muscle,  cut  across  to 
show  the  lingual  nerve  and  the  salivary  ducts  which  lie  beneath  it.  U.  Masseter  muscle  covering  the  angle  of  the 
lower  jaw.    z.  Origin  "f  the  mylohyoid  nerve,  which  is  hidden  by  the  reflected  digastric  and  mylo-hyoid  muscles. 


Fig.  311.— -Qastric  cannula  seen  in  section,  and  key.  A,  outer  flange;  B,  inner  flange;  C,  projecting  points 
by  which  the  outer  can  be  screwed  round  on  the  inner  tubi  .■■■■>  m  to  Increase  the  distance  between  the  flanges. 
d,  i).  1-  the  key  by  which  the  tube  Is  t 1     n  t,  ..f  a  .in  I.-  of  metal,  with  two  slits,  ]>  and  i>,  into 

which  the  projections  0  pass.     It  is  attached  by  a  CrOSB-har  to  a  handle  K,  which  is  about  six  or  eight  inches  long, 
though  cut  short,  in  the  engraving. 


! 


m  Ipptueo  :"'"i 


Plate  CXV. 


Fic:.  314.— Cholesterin. 

PIG.  315.— Point  of  the  instrument  used  fur  puncturing  the  fourth  ventricle  to  produce  diabetes, 


Fk;.  •)(<;.— Aft<r  Bernard.     Section  of   i  rmbuit'i  bead,  ihowlng  Che  direction  taken    oy  the   Inttromenl    In 
a,  earabaUum;  r>,  origin  ol  the  levantb  oatrai  o,    pinji]  cord;  d,  ori 

vagua;  e,  i».iut  w]  ■ .1  ;  g,  the  fifth  uerre  j  Ik, Iltorj 

(■IMl  ;   <,  I  ■  .     1  1    .      1  .1  U  limn  ; 

*,  ooelplta]  raoooi  ilnae;  ',  corpora  quadrigemiiiA ;   ..  .,,     ,  U 


Plate  CXYI. 


V-, 


Fn;.  317.— Arrangement  of  the  cannula  in  a  temporary  pancreatic  fistula.  A,  the  chief  pancreatic  duct  of 
the  dog  directed  transversely;  a,  insertion  of  the  pancreauc  ducts  into  the  intestine;  the  insertion  of  the 
smaller  duct  is  higher  up.  and  is  marked  by  a  line  without  a  letter;  a',  a  branch  of  the  larger  duct  within  the 
Bland;  a",  ligature,  fastening  the  cannula  T  to  the  intestine;//,  is  a  thread  by  which  the  cannula  is  fastened 
pancreatic  duct;  1,  is  the  intestine;  P  P\  the  pancreas  ;  T,  the  silver  cannula;  B,  the  stopcock,  for 
letting  out  juice  which  has  accumulated  in  the  india-rubber  hag ;    V,  an   india-rubber  bag,  tied 

mter  end  of  the  cannula,  and  used  for  collecting  the  .juice. 


-The  left-hand  diagram  shows  the  method  of  stitching  up  the  end  r,f  the  divided  intestine  ao 
in  Thiry's  fistula.    The  right  ban. I  figure  shows  the  method  ol  ether  the  divided 

The  two  black  dots  in  the  middle  of  the  pieces  already  Joined,  Indlc&tethe  position  of  the  mesenterl 
tionld  surround  these  vessels  and  serve  as  a  ligature  for  them.      Five  or  six  similar 

to  Join  the  ..lie  edge,  as  shown  here.    The  two  ends  of  intestine  are  then  pulled  into 
iwn  in  fiir.  319. 
I  the  method  of  applying  the  tin  loin  the  divided  Intestine  in  Thiry's  fistula.    The 

represented  a*  entirely  apart,  but  the  other  half  of  the  circumference  must  i«  undi  1  1 1 

t„  1*  air  ether  in  the  manner  ihown  In  tig.  318. 


.v.  "a 


°? 


o       3     o  OOjO 


3  '  -a 

S3  » 


<8fo 


B*. 


-  ■ 


O' 
1  Milk. 


'  m 


°0l 

.0.  '  V', 
Kill.  3ji.     1 


Plate  CXVII. 


FIG.  326. — Piece  of  glass  drawn  out  to  furm  a  pipette. 


FIG.  327. — A  tube  drawn  out  in  order  to  seal  it.    The  operation  is  completed  by  directing  the  point  of  a  blowpipe 
name  011  the  point  a,  and  drawing  the  two  ends  of  the  tube  rapidly  apart. 


MB   jA— flotation.    The  beaker  Uiupported  on  win  gauw  In  order  to  prevent  it  bom  cracking. 

,  Uon  during  prolonged  ebullition,    k,  the  flank   in  which 

U,e  liquid  condeneer;/,  a  glaee  tube,  wb  andr;  ( end  *,  two  india-rubber 

1.,  ud  from  the  I  In  t,  end 

rmu  taek  into  X,    Any  of  the  oondsnied  liquid  that  ad  the  bend  of  the  gltm  tube  p,  which  li  1 

Ui  the  nj'iH-r  endof  f«ii  eolleoted  in  tbeexnal]  0,  [rnwttit  '<»  the 

M  any  quantltj  "  tlatei  ■"  it,  the  flame    may  iw    rem  ■  raouum  then 

form*  In  K,  and  the  liquid  ruiliei  back  luto  it. 


Platk  CXVIII. 


FIG.  |  used  as  a  water-bath. 

FIG.  331. — Bun  iilator   as    m...i  . 

Qelssler.  a,  is  a  wide  glass  tube  divided  into  two 
parts,  an  upper  and"  lo we:  atal  septum,  from 

which  a  tube  runs  down  nearly  to  the  bottom  of  Che 
lower  one.  The  upper  division  and  paarf  of  the  L 
is  filled  with  mercury.  6,  is  a  glass  tube  passing  through 
the  cork  of  a,  and  f  and  *  with  the  g     pipe 

and  the  burner,  c,  is  an  inner  glass  tube  whose  edges 
are  luted  to  those  of  &  at/,  (/,  is  a  small  hole  in  <•, 
allowing   suffii  ii  ■   through  it  to  1  1 

the  flame  from  being  extinguished.  The  gas  enters 
at  /  and  passes  through  the  inner  tube  c  to  the  burner 
bye,  or  vice  versd.  The  instrumeul  isset  by  warming 
it  to  the  desired  temperature,  and  then  pushing  down 
b  till  the  end  of  c  touches  the  mercury.  The  gas 
is  then  prevented  from  passing  through  <*,  and  only 
enough  passes  through  the  hole  d  to  keep  the  flame 
alive,  till,  the  instrument  becoming  cooler,  the  mercury 
contracts,  and  allows  the  gas  again  to  pass  through 
the  lower  end  of    c. 


FIG.  332.— Water-bath  for  experi- 
ments mi  digestion,  o)  fur  evapor- 
ating a1  a  constant  temperature. 
This  consists  "i"  two  parts,  the 
bath  itself ,  i,  and  an  apparatus,  a, 

for  keeping  the  water  in  the  bath 
at  a  constant  level,  (i,  I-.  . 
flask  containing  water,  b,  c,  is 
i  -lass  tube  open  at  hoth 
ends.  d,e,f,  is  a  bent  tube  with 
limbs  of  equal  length.  The  end. 
e,  ispnf  at  the  level  at  which  the 
watei  in  'Ii.-  bath,  i,  is  to  remain. 
Both  ends,  d  and/,  are  about  an 
inch  below  c,  ami    thus    form  a 

5  S  p] I  difference 

qi  verti- 
cal distance  between  c  and  </,  t>r 
about  an  inch.  Whenever  the 
water  in  i  falls  below  the  level 
of  c,  thesyphon  arts,  and  water 

runs  through    it  nnl  il  the  level  in 

/  i  as  high  as  c,  when  it  ceases. 
ff,  is  opposite  a  thermometer  for 

temperature   of 

the  i«ath.  //,  is  a  gas  regulator. 
The  on.-  represented  here   differs 

somewhat  trom  thai  in  fig,   ;  ;i,  hut. 

re    expensh e   and  has    no 

advantage  0  a   fcheol  her.     t,    is 

anc    or    in).      The     dotted    line 

it  .    covered    ....;.  1 .-  plati   perforai  <l  with  boles,  in  which  bi  it .on 

basins  can  be  put.  The 

rhe perforated  pi 1 ; toved,  and  a  large 

dialyzer,  flg.  v;7,  put  in  Its  place,  when  dig    tion  and  dlarj       are  bo  bi   a sd  or  ai  the   ami    in,..'.     /,  1.  b   tin 

in  which  dj  m    pla  1  d      1  he  boli     in  the  apper  plate  oi  the  nu  1    are 

numbered  '"      '  '"'  ,!  '"  tlie 

lower  plate  are  much  small*  1  than  In  the  upper,  and  lerve  only  to  prevenl  the  tubes  from    Up] 


1  -,-  of  the  syphon  in  v. 


Plate   CXIX. 


FIG.  334-—  Screw-press.  The  substance  from  which  the 
fluid  is  to  be  expressed  is  wrapped  iu  strong  flannel  or 
calico,  and  the  liquid  which  oozes  out  is  collected  as  it 
runs  from  the  small  spout. 

tPtG-335' — Bunsen's  witter  air-pump.  This  consists  of  a 
wide  glass-tube  at  into  which  another  tube  b,b',b",  passes 
air-tight,  c.  is  au  india-rubber  tube  connecting  a  with  the 
w;tter  Supply,  d,  is  a  clamp  to  stop  the  flow  of  water 
through  c.  e,  is  another  clamp  to  regulate  the  flow.  /, 
is  a  reservoir  to  prevent  any  water  which  may  accidentally 
come  over  from  getting  into  J.  <f,  is  a  plug  to  let  out 
any  water  from  /.  7*.  is  a  screw  for  connecting  a  air-tight 
to  a  piece  of  tubing,  which  should  pass  32  feet,  if  jwssible, 
below  the  level  of  a.  i,  is  a  piece  of  strong  india-rubber 
tubing  to  connect  the  air-pump  withy,  the  bell-jar,  to  be 
exhausted.  The  water  rushes  in  at  c  and  down  h,  carrying 
bubbles  of  air  with  it,  as  shown  opposite  a,  till  the  exhaus- 
tion is  complete,  a  is  represented  as  half  full  of  water. 
k,  a  funnel  fixed  air-tight  in  the  india-rubber  stopper  of  j. 
I,  a  small  cone  of   platinum    foil  to    prevent    the   filter 

from  being  broken,  m,  a  plate  of  ground  glass,  n,  a  beaker  to  receive  the  filtrate.  N,  a  manometer  to  measure 
the  degree  of  exhaustion,  o.  apiece  of  platinum  foil  <>f  the  proper,  size  and  shape  to  make  the  cone,  /.  #,  a  mould, 
and  t,  a  stamp,  to  give  the  proper  Bhape  to  the  cone,  Z.  /»,  is  a  cone  of  porous  earthenware  used  as  a  funnel.  7,  is  a 
piece  of  wide  india-rubber  tubing  stretched  over  the  funnel  r,  and  holding  the  cone  j>  air-tight,  r,  is  a 
funnel  inserted  into  the  Btoppex  Of  a  bell-jar.  The  bell-jar  may  either  be  exhausted  by  means  of  a  tube  in  the 
stopper*  like  j,  or  by  ■<  tubulature  in  tin-  side,  as  is  supposed  to  be  the  case  with  thai  holding  r. 


l\ Iso  1 1  bo  keep  liquldsatthe 

I  then     Luini  1       Om  ol 
•enlng  above,  mi  below,  which  la  closed  b  b  the  tube 

. 

lee  with  which  the  metal  fui I  Oiled,    rh<    """'  '"""  bae  a  copper  fu  1  of  the  dotted  Mue 

itn,j  ^  o,,    ■  I    ■  ' oded  by  the  water  oi  Ice 

then  tore  xuA  <■■  removed  n  Ith  great 

place  whirl,  lei*  ■  n  the  othei  form  [seni]        ■' 

■  he     The  uppi  r  figure  si  tysei  e*lth  the  1 1 n1  papt  -     tret  bed 


Plate  CXX. 


Fig.  339. — Hut  ait  bath  fur  drying  precipi- 
tates, &c. 


FIG.  340.— Bell-jar  aud  dish,  containing  sulphuric  acid 
for  drying  aud  cooling  substances. 


FIG.  342.— Platinum  triangle  stretched 
upon  a  larger  iron  one  for  ignition. 

FIG.  343.— Specific   gravity  bottle. 

FIG.  344. — Specific  gravity  bottle. 

FIG.  345. — Bottle  for  taking  the  spe- 
cific gravity  of  small  quantities  of 
liquids. 


1 


Plate  CXXI. 


-  tie  nulDi  fl»»k.   {tram  Huit.ui»  Handbook  "f  Volumetric  Aoalyil*.) 
■tat  mixer.   (From  Button'!  Handbook ol  Volumetric  AnalyiU.) 


Tlate  CXXII. 


50  CC 


10  CC 


3 


PBj.  3(8.-1  !      "  Bnthm'i  Handbook  "f  Volumetric  ArmlyniH.) 

Bandbook  of  7oluin*trio  Ajwlyrii.] 


Tlate  CXXIII. 


Pig.  350 


Fir;.  351. 


FI8.  350. From  Sutton's  Handbook  of  Volumetric  Analysis.  The  figure  to  the  left  shows  the  elliptical  appear- 
ance presented  by  aline  round  a  burette  or  by  the  surface  of  fluid  in  it.  when  the  eye  of  the  observer  is  above 
it.  The  figure  to  the  right  shows  the  curved  surface  of  fluid  in  a  tube.  In  reading  off  its  level,  the  lower  border 
of  the  dark  zone  must  coincide  with  the  graduation  of  the  burette  as  ill  the  figure,  where  the  dark  line  stretch- 
ing across  the  tube  indicates  one  of  the  graduated  lines  upon  it. 

FIG.  351.— Erdmann's  float.    (From  Sutton's  Handbook  of  Volumetric  Analysis.) 


!  "    PiF- 

"  t:ji 

1 

llr 

^-=^j 

|ii..mni"imi 

i' ii-'n 

i< 

V  *"■"•'> >'•"!» 


no 


PIO.  352.— Stand  for  burettes.    (From  Sntton's  rTaudbookof  Volumetric  Analj  I    | 

Kii;.  35  (.-  , harameter.    a  and  0  are  two  N I's  prisms, of  which,  i,  is  fixed,  and  the  other,  a,  U  movable' 

t,  ii  an  Indicator  t.,  show  the  position  "f  a.    «  »,  Is  a  circular  graduated  disk  lor  measuring  the  rotation  ■•!  •<.    g,  Is  I 

nompoa  doi  two  pieces,  v.  Is  a  single  plate  "f  quartz.  Sand  ".  are  the  soak  and  vernier  of  thi mpen- 

sator.    r,  the  screw  bj  which  thee  mi  ensatoi  Ii  ai -   '.  ars  the  two  quarts  prisms  of  whioh  the  com- 

ug  the  tube  of  fluid  for  examination. 


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J-75 
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1. 00 
2.00 
2.00 
3.00 

•75 
5.00 

5-5° 
1.50 
.50 
3.00 
1,00 
2.25 
2.25 


Laboratory. 


Bowman's  Practical. 
Leffmann's  Compend.     - 
Muter.     Pract.  and  Anal. 
Richter's  Inorganic. 

Organic. 

Stammer.     Problems.     - 
Sutton.     Volumetric  Anal 
Tidy.     Handbook  of. 
Trimble.     Analytical. 
Vacher's  Primer  of. 
Valentin.    Qualt.  Analy. 
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Watts.     (Fowne's)  Inorg. 

(Fowne's)  Organ. 

Wolff.  Applied  Medical  Chem- 
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Meigs  and  Pepper's  Treatise. 5. bo 
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Hughes.  Practice.  2  Pts.  Ea.  1.00 
Landis.  Obstetrics.  3d  Ed.  1.00 
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Morris.     Gynecology.     -  1.00 

Potter's    Anatomy,   including 
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Ward's  Chemistry.     2d  Ed.     1.00 

DEFORMITIES. 

Churchill.     Face  and  Foot.  3.50 

Coles.    Of  Mouth.           -  4.50 

Prince.     Orthopaedics.     -  4.50 

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Flagg.     Plastics.      -        -  4.00 

Gorgas.     Dental  Medicine.  3.25 

Harris.     Principles  and  Prac.  6.50 

Dictionary  of.       -  6.50 

Heath.     Dis.  of  Jaws.     -  4.50 

Lectures  on  Jaws.  1.00 

Leber    and     Rottenstein. 

Caries.     -        -        -         -  1.25 

Richardson.     Mech.  Dent.  4.50 

Stocken.     Materia  Medica.  2.50 

Taft.    Operative  Dentistry.  4.25 

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Talbot.     Irregularities  of  the 

Teeth,     ....  2.00 

Tomes.     Dental  Surgery.  5.00 

Dental  Anatomy.  

White.    Mouth  and  Teeth.  .50 

DICTIONARIES. 
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Handbook,  -  .50 

Liebreich.    Atlas  of  Ophth.    15.00 
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Monthly. 

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Packard.    Sea  Air  and  Bath'g.   .50 


2  50 
2.00 


1.25 

50 


•  So 
■5° 
•5° 

•75 
.50 
.50 
1. 00 

•  50 
.50 
.50 
•50 
•75 
■S3 
.50 

1. 00 
.50 


.25 

5.00 
3-5° 
1.50 
1.25 


Solly.     Colorado  Spiings. 

HEART. 
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Fothergill.     Diseases  of. 
Keating  6k  Edwards.     - 
Sansom.     Diseases  of.     - 
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(  See  Microscope  and  Pathology. 
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Frankland.     Water  Analysis.  1.00 


Fox.     Water,  Air,  Food. 
Lincoln.     School  Hygiene. 
Parke's  Hygiene.  7th  Ed. 
Wilson's  Handbook  of.  - 

Domestic.     - 

KIDNEY  DISEASES. 
Beale.     Renal  and  Urin. 
Edwards.     How  to  Live  with 

Pright's  Disease.    - 
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Ralfe.     Dis.  of  Kidney,  etc. 
Tyson.     Blight's  Disease. 

LIVER. 
Habershon.     Diseases  of. 
Harley.     Diseases  of. 

LUNGS  AND  CHEST. 

See  J'iiy.  Diagnosis  and  Throat. 

Williams.     Consumption.        5.00 

MARRIAGE. 
Ryan.     Philosophy  of.     -  J. 00 

MATERIA  MEDICA! 

Biddle.     10th  Ed.    - 
Charteris.     Manual  of.  - 
Gorgas.     Dental.     2d  Ed. 
Merrell's  1  tigest. 
Phillips.     Vegetable,  Organic 

and  Animal.     New  Ed.  7.50 

Potter's  Compend  of.  4th  Ed.  1.00 

Handbook  of.  -  3.00 

Roberts'  Compend  of.     -  2.00 


4.00 

•  5° 

4.50 

2.75 
1. 00 

1-75 

.50 
3.00 
2.75 

3-5° 

1.50 
3.00 


4.00 


3.00 
4.00 


CLASSIFIED  LIST  OF  P.  BLAK1ST0N,  SON  &*  CO.'S  PUBLICATIONS. 


2-75 
2.75 
3.00 


-MEDICAL  JURISPRUDENCE. 
Abercrombie's  Handbook,  2.50 
Reese's  iext-bookof  3.or;Sh.  3.50 
Woodman  and  Tidy's  Treat- 
ise, including  Toxicology.  7.50 
.MICROSCOPE. 
Beale.     How  to  Work  with.      7.50 

In  -Medicine.         -  7.50 

Carpenter.     The  Microscope. 

Lee.     Yade  Mecum  of.    -  3.00 

MacDonald.     Examination  of 

Water  by.        - 
Martin.     Mounting. 
Wythe.     The  -Microscopist. 
MISCELLANEOUS 
Allen.     The  Soft  Palate. 
Beale.     Lite  Theories,  etc. 

Slight  Ailments. 

Bioplasm. 

■     Lite  and  Vital  Action. 

Black.     Micro-Organisms. 
Davis.     Biology. 
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Vaccination. 

Gross.     Life  of  Hunter. 
Haddon.     Embryology.    - 
Hare.    Tobacco. 
Henry.     Anaemia.   - 
Hodge.     Foeticide.   - 


1.25  ' 

2.25  1 

2.00  j 

1-5°  I 

.50 

•5° 

1-25   I 

6.00 

Paper,  .50 

•75 
Paper,  .30 
Holden.   The  Sphygmograph.  2.00 
Kane.     Opium  Habit.      -  1.25 

MacMunn.  The  Spectroscope  3.00 
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Smythe.  Med'l  Heresies.  1.25 
Sutton.    Ligaments.         -  1.25 

Wickes.  Sepulture.  -  1.50 

NERVOUS  DISEASES,  Etc. 
Buzzard.     Ner.  Affections.       5.00 
!■  lower.    Atlas  of  Nerves.         3.50 
Gowers.    Manual  of  In  1  vol.  6.50 
Dis.  of  Spinal  Cord.       

Diseases  of  Brain.  2.00 

Epilepsy.      -         -  

Page.     Injuries  of  Spine.  3.50 

Radcliffe.  Epilepsy,  Pain,  etc.  1.25 
Wilks.     Nervous  Diseases.       6.00 

NURS 

Cullingworth.     Manual  of.  1.00 

Monthly    Nursing.  .50 

Domville's  Manual.         -  .75 

Hood.     Lectures  to  Nurses.  1.00 

Liickes.     Hospital  Sisters.  1.00 

Temperature  Charts.    -  .50 

OBSTETRICS. 

Bar.  Antiseptic  Obstet.  1.7s 
Barnes.  Obstetric  Operations.  3.75 
Cazeaux  and  Tarnier.     New 

Ed.     Colored  Plates.     -  11.00 

Galabin's  Manual  of.       -  3.00 

Glisan's 'Text-book.    2d  Ed.  4.00 

Landis.     Compcm.!.         -  1.00 

Meadows.     Manual.       -  2.00 

Rigby.     Obstetric  Mem.  .50 

Scnultze.     Diagrams.      -  25.00 

Tyler  Smith's  1  reatise.  4.00 

Swayne's  Aphorisms       -  1.25 

I  1  OLOGY. 

Holden's  Text-book.  -  6.00 
PATHOLOG  >LOG*. 
Aitken.  The  Ptomaine*,  etc.  1.00 
Bowlby 

Gibbes.                              -  1.75 

Gillian.                        of.  -  2.00 

Paget's  Surg  7.'-o 
Kind!.'                       eraL 

Sutton.  th.  -  4.50 
Virchow.     I' 

'                        "/■  -  4-oo   I 

Wilkes  and  Moxon.    -  6.00  I 

I'll  A  KM  . 
Bcasley's  Di  ts.    2.25 

1  ormulary,  -       -         2.25  [ 

Flilckiger.    <  's.  1.50  I 

Kirby.  ies.  2.25   1 

Mackenzie.  Char.  of  Thr, . 

Merrcll'k  Digest.  -        -  4  </, 

Piesse.  -  5.50  1 


Proctor.     Practical  Pliarm.       4.50 
Roberts.     Compend  of.  2.00 

Stewart's  Compend.    2d  Ed.    1.00 
Tuson.     Veterinary  Pharm.      2.50 

PHYSICAL  DIAGNOSIS 
Bruen's  Handbook.     2d  Ed.     1  50 

PHYSIOLOGY. 
Beale's  Bioplasm.    -        -  2.25 

Brubaker's  Compend.     lllus. 

4th  EJ.    -  1. 00 

Kirkes'   nth    Ed.     (Author's 

Ed.)  Cloth,  4.00;  Sheep,  5.00 
Landois'  Text-book.  2d  Ed.  6.50 
Sanderson's  Laboratory  B'k.  5.00 
Sterling.  Practical  Phys.  2.25 
Tyson's  Cell  Doctrine.    -  2.00 

Yeo's   Manual.    3d  Ed.    CI.,  3.00; 
Sheep,  3.50 


Aitken. 
Black. 
Reese. 
Tanner 


POISONS. 

The  Ptomaines,  etc. 


1  50 


•75 


1.25 


1.25 


Formation  of. 
Toxicology. 
Memoranda  of. 
PRACTICE. 
Beale.     Slight  Ailments. 
Charteris.     Handbook  of. 
Fagge's  Practice.     2  Vols. 
Fenwick's  Outlines  of.    - 
Hughes.  Compend  of.  2  Pts.  2.00 
Physician's  Ed.  Inset.  1  Vol.  2.50 
Roberts.     Text-book.     New 

Ed.  -  5.00 

Tanner's  Index  of  Diseases.     3.00 
Warner's  Case  Taking.  1.75 

PRESCRIPTION  BOOKS. 
Beasley's  3000  Prescriptions.    2.25 

Receipt  Book.        -  2.25 

Formulary.     -         -  2.25 

Pereira's  Pocket-book.  1.00 

Wythe's  Dose  and  Symptom 

Book.     17th  Ed.      Just  out.  1. 00 
RECTUM  AND  ANUS. 
Allingham.    Diseases  of.  1.25 

SKIN  AND  HAIR. 
Anderson's  Text-Book.  4  50 

Bulkley.    The  Skin.        -  .50 

Cobbold.     Parasites.        -  5.00 

Van    Harlingen.      Diagnosis 

ami  Treatment  of  Skin  Dis.    1.75 
Wilson.     Skin  and  Hair.  1.00 

STIMULANTS  &  NARCOTICS. 
Hare,  Tobacco.  Paper,  .50 

Kane.    Opium  Habit,  etc 
Kerr.     Inebriety. 
Lizars.     On  Tobacco. 
Miller.     On  Alcohol 
Parrish.     Inebriety. 

SURGERY. 
Butlin.      Surg,    of    Malignant 

^e^.  ...  4.00 
Heath's  Operative.  -  12.00 
Minor.    8th  Ed.      -  2.00 

Diseases  of  Jaws.  4.50 

Lectures  on  Jaws.  

Horwitz.   Compend.    3d  Ed.    1.00 

Jacobson.     Operative  Surg,     

Porter's    Surgeon's    Pocket- 

-        •         -        -  2.25 

Pye.     Surgical  Handicraft.        5.00 
Roberts.     Surgical  Delusions.    .50 

(A.  S.)   Club-Foot.  .50 

Smith.     Abdominal  Surg.       

Swain.  s.     1.50 

Walsham.     Practical  Surg.     3  00 
Watson's  Amputations.  5.50 

1  «OLOGICAL  BOOKS. 

Sec  also  Chemistry. 
Camcr'  bes.  2.50 

Gardner.     Brewing,  etc.  1.7; 

Gardner.     A-  tc.      1.75 

I  ".     r.75 

Groves  and  Thorp.    CI. 

1  .i|      I  r:,  hnoiogy.       Vol.  I . 

I  ticl  .    Mills.  -        -       -       

Overman.     Mineralogy.  too 

Pienae.    Perfumery,  etc.  5.50 

Piggott.    On  Copper.     -  1.00 


1.25 


.SO 

.50 
k.25 


THERAPEUTICS. 
Biddle.     10th  Ed.    -        -  4.00 

Cohen.     Inhalations.        -  1.25 

Field.  Cathartics  and  Emetics.  1.75 
Headland.  Action  of  Med.  3x0 
Kirby.  Selected  Remedies.  2.25 
Kidd.     Laws  of.        -         -  1.25 

Mays.     Therap.  Forces.  1.25 

Ott.  Action  of  Medicines.  2.00 
Phillips.     Vegetable.       -  7.50 

Potter's  Compend.  -  1.00 

,  Handbook  of.  3.00  ;  Sh.  3.  50 

Starr,  Walker  and  Powell. 

Phys.  Action  of  Meds.   -  .75 

Waring's  Practical.         -  3.00 

THROAT  AND  NOSE. 
Cohen.     Throat  and  Voice. 

Inhalations. 

Greenhow.     Bronchitis. 
James.     Sore  1  hroat 
Journal  of  Laryngology. 
Mackenzie.    1  hroat  and  Nose. 

New    Ed.     Complete   in  one 
vol.     New  lllus.,  etc.       -        

The  OZsophagus,  Naso- 
pharynx, etc.  -  3.00 

Larynx.  -         -  1.25 

Pharmacopoeia.    -  1.25 

Potter.     Stammering,  etc.  1.00 

Woakes.  Post-Nasal  Catarrh.  1.50 

■ Nasal  Polypus,  etc.  1  25 

Deafness,  Giddiness,  etc 

TRANSACTIONS   AND 

REPORTS. 

Penna.  Hospital  Reports.      1.25 

Power  and  Holmes'  Reports.    1.25 

Trans.  College  of  Physicians.  3.50 

Amer.  Surg.  Assoc.        4.00 

URINE  &  URINARY  ORGANS. 
Acton.     Repro.  Organs.  2.00 

Beale.     Urin.  &  Renal  Dis.      1.75 

Urin.  Deposits.    Plates.  2.00 

Holland.     The  Urine.     -  .50 

Legg.     On  Urine.     -        -  .75 

Marshall  and  Smith.  Urine.  1.00 
Ralfe.  Kidney  and  Uri.  Org.  2.75 
Thompson.  Urinary  Organs.  1.2s 

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Cooper.     Syphilis.  -        -  3.50 

Durkee.     Gonorrhoea.     -  3.50 

Hill  and  Cooper's  Manual.  1.00 
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VETERINARY   PRACTICE. 
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VISITING   LISTS. 
Lindsay    and     Blakiston's 
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WATER. 
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MacDonald.        "         " 

WOMEN,  DISEASES  OF. 

Byford's  Text-hook.  4th  Ed.    s.oo 

Uterus.   - 
Dillnberger.     and  Children. 
Doran.  rations, 

Duncan.    Sterility. 
Galabin.     Diseases  of.     - 
Hodge.     Not.-  Bool 

Tumol  1. 
Mom.. 
Savage.     I'.  . 

Scanzoni.  of.  4.00 

Tilt,      t  L25 

Winckel,  by  Parvin.    Manual 

of.     illu...         CI.  . 


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THE  POLYCLINIC.     Vol.  V. 

A  Monthly  Journal  of  Medicine  and  Surgery.  Doubled  in  Size  Without  Increase  of  Price. 

$1.00  PER  ANNUM.      SAMPLE  COPIES  FREE. 

EDITOR-IN-CHIEF,    HENRY    LEFFMANN,    M.  D. 

The  Polyclinic  for  1888  will  Contain 

More  original  and  clinical  articles  prepared  especially  for  it  by  prominent  writers  than  any  other 
Medical  Journal  of  its  size  and  price.  Arrangements  have  been  made  to  secure  reports  of  clinics 
by  well-known  lecturers  in  New  York,  Chicago  and  other  cities  as  well  as  in  Philadelphia.  A 
number  of  articles  on  practical  subjects  will  also  appear.  A  series  of  articles  by  Dr.  J.  Henry  C. 
Simes,  on  various  phases  of  Diseases  of  the  Urinary  Organs,  will  be  worthy  special  attention. 
Prof.  Thos.  T.  Mays  will  contribute  a  number  of  articles  on  Therapeutical  Subjects. 

REGULAR  CONTRIBUTORS.— Chas.  H.  Burnett,  m.d.  (Otology),  Arthur  Van  Har- 
lingen,  M.D.  {Skin  Diseases),  John  B.  Roberts,  M.D.  {Surgery),  Thos.  J.  Mays,  M.D.  (Therapeu- 
tics), J.  Henry  C.  Simes,  M.D.  (Surgery),  Chas.  K.  Mills,  M.D.  (ATervous  Diseases),  and  others. 

Clinical  Lectures,  Papers  and  Original  Articles  appeared  by  the  following  gentlemen  during 
1887:— 

Goodell  (Prof.  Win.),  Univ.  of  Penna.  Bantock  (Geo.  Granville,  f.r.c.s.),  London. 

Meigs  (Dr.  A.  V.),  Phys.  to  Penna.  and  Child.  Hosp.    ]    Pepper  (Win.,  m.d.  ),  Prof.  Pract.  of  Med.  Univ.  of  Pa. 

Osier  (Prof.  Wm.),  Univ.  of  Penna.  Carter  (Dr.  Landon  Gray),  Prof,  of  Men.  and  Nerv. 

Willard  (Dr.  DeForest).  Dis.,  N.  Y.  Polyclinic. 

Mittendorf  (Dr.  \V.  M.),  Surg,  to  N.  Y.  Eye  and  Ear       Robison  (Dr.  John  A.).  Rush  Med.  Coll.,  Chicago. 

Infirmary.  j     Pavy  (F.  W.,  f.r.s.),  London. 

Sinkler  (Dr.  Wharton),  Phys.  to  Orth.  Hosp.  (    Price  (Dr.  Joseph),  Phys.  to  Preston  Retreat,  Phila. 

Longstreth   (Dr.  Morris),   Pathologist  to  Jefferson 

Med.  Coll. 
White  (Wm.  Hale,  m.d.),  Guy's  Hospital,  London. 
Ashhurst  (John,  Jr.),  Prof.  Clin.  Surg.,  Univ.  of  Pa. 
Packard  (Dr.  John  H.),  Surg,  to  Penna.  Hospital. 
Parvin  (Theophilus),  Prof.  Obst.  and  Dis.  of  Women, 

Jefferson  Med.  Coll. 
Wyeth  (John  A.),  Prof,  of  Surg.,  N.  Y.  Polyclinic. 
Reese    (Dr.  John   J.),   Prof,  of  Med.  Jurisprudence, 

Univ.  of  Pa. 
Spender  (John  Kent,  m.d.),  Bath,  England. 


Browne  (Lennox,  f.r.c  s.),  London. 

Brubaker  (Dr.  A.  P.),  Dem.  of  Physiology  Jefferson 

Med.  Coll. 
Steele  (D.  A.  K.,  m.d.),  Prof.  Orth.  Surg.  Coll.  Phys. 

and  Surg.,  Chicago. 
McMurtrie  (Dr.  L.  S.),  Danville,  Ky. 
Tyson  (Dr.  Jas),  Prof.  Pathology,  Univ.  of  Penna. 
Hartshorne  (Dr.  Henry). 
DaCosta  (Dr.  John  C),  Gynaecologist  to  Jeff.  Med. 

Coll.  Hosp. 
Henry  (Dr.  F.  P.),  Phys.  to  Episcopal  Hospital,  Phila. 

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applied  to  the  Diseases  and  Accidents  Incident  to  Women.  By  W.  H.  Byford, 
a.m.,  m.d.,  Professor  of  Gynaecology  in  Rush  Medical  College  and  of  Obstetrics 
in  the  Woman's  Medical  College  ;  Surgeon  to  the  Woman's  Hospital ;  Ex-Presi- 
dent American  Gynaecological  Society,  etc.,  and  Henry  T.  Byford,  m.d.,  Sur- 
geon to  the  Woman's  Hospital  of  Chicago ;  Gynaecologist  to  St.  Luke's  Hos- 
pital ;  President  Chicago  Gynaecological  Society,  etc.  Fourth  Edition.  Revised, 
Rewritten  and  Enlarged.  With  306  Illustrations,  over  100  of  which  are  original. 
Octavo.     832  pages.  Cloth,  $5.00;  Leather,  $6.00 

On  the  Uterus.     Chronic  Inflammation  and  Displacement.  Cloth,  $1.25 

CARPENTER.  The  Microscope  and  Its  Revelations.  By  W.  B.  Carpenter, 
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tions and  Lithographs.  In  Press. 

CARTER.  Eyesight,  Good  and  Bad.  A  Treatise  on  the  Exercise  and  Preservation 
of  Vision.  By  Robert  Brudenell  Carter,  f.r.c.s.  Second  Edition,  with  50 
Illustrations,  Test  Types,  etc.     i2mo.  Paper,  .75;   Cloth,  $1.25 

CAZEAUX  and  TARNIER'S  Midwifery.  With  Appendix,  by  Munde.  Eighth 
Revised  and  Enlarged  Edition.  With  Colored  Plates  and  numerous  other 
Illustrations.  The  Theory  and  Practice  of  Obstetrics ;  including  the  Diseases 
of  Pregnancy  and  Parturition,  Obstetrical  Operations,  etc.  By  P.  Cazeaux, 
Member  of  the  Imperial  Academy  of  Medicine,  Adjunct  Professor  in  the  Faculty 
of  Medicine  in  Paris.  Remodeled  and  rearranged,  with  revisions  and  additions, 
by  S.  Tarnier,  m.d.,  Professor  of  Obstetrics  and  Diseases  of  Women  and 
Children  in  the  Faculty  of  Medicine  of  Paris.  Eighth  American,  from  the 
Eighth  French  and  First  Italian  Edition.  Edited  and  Enlarged  by  Robert 
J.  Hess,  m.d.,  Physician  to  the  Northern  Dispensary,  Phila.,  etc.,  with  an  Ap- 
pendix by  Paul  F.  Munde,  m.d.,  Professor  of  Gynaecology  at  the  New  York 
Polyclinic,  and  at  Dartmouth  College ;  Vice-President  American  Gynaecological 
Society,  etc.  Illustrated  by  Chromo-Lithographs,  Lithographs,  and  other  Full- 
page  Plates,  seven  of  which  are  beautifully  colored,  and  numerous  Wood  En- 
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CHARTERIS.  The  Practice  of  Medicine.  A  Handbook.  By  M.  Charteris, 
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Microscopic  and  other  Illustrations.  Cloth,  $1.25 

Materia  Medica  and  Therapeutics.    A  Manual  for  Students.         In  Press. 

CHAVASSE.  The  Mental  Culture  and  Training  of  Children.  By  Pye  Henry 
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CHURCHILL.  Face  and  Foot  Deformities.  By  Fred.  Churchill,  m.d., 
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and  Two  Colored  Lithographs.     8vo.  Cloth,  $3.50 


MEDICAL  AND  SCIENTIFIC  PUBLICA  TIONS.  9 

CLEVELAND'S  Pocket  Dictionary.  A  Pronouncing  Medical  Lexicon,  containing 
correct  Pronunciation  and  Definition  of  terms  used  in  medicine  and  the  col- 
lateral sciences,  abbreviations  used  in  prescriptions,  list  of  poisons,  their  anti- 
dotes, etc.  By  C.  H.  Cleveland,  m.d.  Thirty-second  Edition.  Very  small 
pocket  size.  Cloth,  .75;  Tucks  with  Pocket,  $1.00 

COHEN  on  Inhalation,  its  Therapeutics  and  Practice,  including  a  Description  of 
the  Apparatus  Employed,  etc.     By  J.  Solis-Cohen,  m.d.     With  cases  and  Illus- 
trations.    A  New  Enlarged  Edition.      i2mo.  Paper,  .75  ;  Cloth,  $1.25 
The  Throat  and  Voice.    Illustrated,    nmo.  Cloth,  .50 

COLES.  Deformities  of  the  Mouth,  Congenital  and  Acquired,  with  Their  Me- 
chanical Treatment.  By  Oakley  Coles,  m.d. ,  d.d.s.  Third  Edition.  83  Wood 
Engravings  and  96  Drawings  on  Stone.     8vo.  Cloth,  $4.50 

COOPER  on  Syphilis  and  Pseudo-Syphilis.  By  Alfred  Cooper,  f.r.c.s.,  Sur- 
geon to  the  Lock  Hospital,  to  St.  Marks,  and  to  the  West  London  Hospitals. 
Octavo.  Cloth,  53.50 

COLLIE,  On  Fevers.  A  Practical  Treatise  on  Fevers,  Their  History,  Etiology, 
Diagnosis,  Prognosis  and  Treatment.  By  Alexander  Collie,  m.d.,  m.r.c°p.,' 
Lond.  Medical  Officer  Homerton  Fever  Hospital,  and  of  the  London  Fever 
Hospital.    With  Colored  Plates.    Being  Volume 3,  Practical  Series.     Cloth,  $2.50 

CULLINGWORTH.    A  Manual  of  Nursing,  Medical  and  Surgical.    By  Charles 

J.  Cullingworth,  m.d.,  Physician  to  St.  Mary's  Hospital,  Manchester,  England. 

Second  Edition.     With  18  Illustrations.     i2mo.  Cloth,  $1.00 

A  Manual  for  Monthly  Nurses.    Third  Edition.    32010.  Cloth,  .50 

DAVIS.  Biology.  An  Elementary  Treatise.  By  J.  R.  Ainsworth  Davis,  of 
University  College,  Aberystwyth,  Wales.     Thoroughly  Illustrated.     i2mo. 

Nearly  Ready. 

DAY.     Diseases  of  Children.    A  Practical  and  Systematic  Treatise  for  Practitioners 

and  Students.     By  Wm.  H.  Day,  m.d.     Second  Edition.     Rewritten  and  very 

much  Enlarged.     8vo.     752  pp.     Price  reduced.  Cloth,  #3.00;  Sheep,  $4.00 

On  Headaches.     The  Nature,  Causes  and  Treatment  of  Headaches.     Fourth 

Edition.     Illustrated.     8vo.  Paper,  .75  ;   Cloth,  $1. 25 

DILLNBERGEK.  .On  Women  and  Children.  The  Treatment  of  the  Diseases  Pecu- 
liar to  Women  and  Children.     By'Dr.  Emil  Dillnberger.    121110.    Cloth,  $1.50 

DOMVILLE.  Manual  for  Nurses  and  others  engaged  in  attending  to  the  sick  By 
Eu.  J.  Domville,  m.d.     Fifth  Ed.     With  Recipes  for  Sick-room  Cookery,  etc. 

Cloth,  .75 

DORAN.   Gynaecological  Operations.   A  Hand-book.   By  Aluan  Doran,  f.r.c.s., 

t.  Surg,  to  the  Samaritan  free   Hospital  for  Women  and  Children,  London! 

Illustrations.     8vo.  Cloth  4  co 

DULLES.  What  to  Do  First,  In  Accidents  and  Poisoning.  By  C.  W.  Dulles,  m.d. 
Third  Edition,  Enlarged;  with  new  Illustrations.  Cloth.  .7c 

DUNCAN,  On  Sterility  in  Women.  By  J.  Mathews  Duncan,  m.d.,  ll.d.,  Obstetric 
Physician  to  St.  Bartholomew's  Hospital,  etc.     Octavo.  Cloth,  #2.00 

DUE.KEE,  On  Gonorrhoea  and  Syphilis.  By  Silas  Dukkee,  m.d.  Sixth  Edition. 
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FIELD.  Evacuant  Medication— Cathartics  and  Emetics.  By  Henry  M,  Field 
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ber'. .  oi  Boston,  etc.    i2mo.    288  pp.  Cloth  fei. ye 


10  P.  BLAKISTON,  SON  <5-  CO.'S 

EDWARDS.     Bright's    Disease.     How  a  Person  Affected  with  Bright's  Disease 

Ought  to  Live.    By  Jos.  F.  Edwards,  m.d.     2d  Ed.     Reduced  to       Cloth,  .50 

Malaria:    What  It  Means;    How  to  Escape  It;  Its  Symptoms;  When  and 

Where  to  Look  For  It.    Price  Reduced  to  Cloth,  .50 

Vaccination  and  Smallpox.     Showing  the  Reasons  in  favor  of  Vaccination, 

and  the  Fallacy  of  the  Arguments  advanced  against  it,  with  Hints  on  the 

Management  and  Care  of  Smallpox  patients.  Cloth,  .50 

FAGGE.  The  Principles  and  Practice  of  Medicine.  By  C.  Hilton  Fagge,  m.d., 
f.r.c.p.,  f.r.m.c.s.,  Examiner  in  Medicine,  University  of  London;  Physician  to, 
and  Lecturer  on  Pathology  in,  Guy's  Hospital ;  Senior  Physician  to  Evelina  Hos- 
pital for  Sick  Children,  etc.  Arranged  for  the  press  by  Philip  H.  Pve  Smith, 
m.d.,  Lect.  on  Medicine  in  Guy's  Hospital.  Including  a  section  on  Cutaneous 
Affections,  by  the  Editor;  Chapter  on  Cardiac  Diseases,  by  Samuel  Wilkes,  m.d., 
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York  Medical  yournal. 

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Lancet  and  Clinic. 

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FENWICK'S  Outlines  of  Practice  of  Medicine.  With  Formulae  and  Illustra- 
tions.    By  Samuel  Fenwick,  m.d.      121110.  Cloth,  $1.25 

FLAGG'S  Plastics  and  Plastic  Filling;  As  Pertaining  to  the  Filling  of  all  Cavities 
of  Decay  in  Teeth  below  Medium  in  Structure,  and  to  Difficult  and  Inaccessible 
Cavities  in  Teeth  of  all  Grades  of  Structure.  By  J.  Foster  Flagg,  d.d.s.,  Pro- 
fessor in  the  Philadelphia  Dental  College.     8vo.     Second  Ed.  Cloth,  $4.00 

FLOWER'S  Diagrams  of  the  Nerves  of  the  Human  Body.  Exhibiting  their 
Origin,  Divisions  and  Connections,  with  their  Distribution  to  the  various  Regions 
of  the  Cutaneous  Surface,  and  to  all  the  Muscles.  By  William  H.  Flower, 
f.r.c.S.,  f.r.s. ,  Hunterian  Professor  of  Comparative  Anatomy,  and  Conservator 
of  the  Museum  of  the  Royal  College  of  Surgeons.  Third  Edition,  thoroughly 
revised.     With  six  Large  Folio  Maps  or  Diagrams.     4to.  Cloth,  $3.50 

FLUCKIGER.  The  Cinchona  Barks  Pharmacognostically  Considered.  By 
Professor  Friedrich  Fluckiger,  of  Strasburg.  Translated  by  Frederick  B. 
Power,  ph.d.,  Professor  of  Materia  Medica  and  Pharmacy,  University  of  Wis- 
consin.    With  8  Lithographic  Plates.     Royal  octavo.  Cloth,  $1.50 

FOTHERGILL.  On  the  Heart  and  Its  Diseases.  With  Their  Treatment.  In- 
cluding the  Gouty  Heart.  By  J.  Milner  Fothergill,  m.d.,  Member  of  the 
Royal  College  of  Physicians  of  London.     2d  Ed.    Rewritten.     8vo.    Cloth,  $3.50 

FOX.  Water,  Air  and  Food.  Sanitary  Examinations  of  Water,  Air  and  Food. 
By  Cornelius  B.  Fox,  m.d.    no  Engravings.    2d  Ed.,  Revised.        Cloth,  $4.00 

FOX   AND   GOULD.     Compend  on  Diseases  of  the  Eye  and  Refraction, 

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Assistant,  Gphthalmological  Department,  Jefferson  Medical  College  Hospital ; 
Ophthalmic  Surgeon,  Germantown  Hospital,  Philadelphia ;  late  Clinical  Assistant 
at  Moorfields,  London,  England,  etc.,  and  Geo.  M.  Gould,  a.b.  60  Illustrations. 
Being  No.  8,  ?  Quiz- Compend  f  Series.  Cloth,  $1.00 

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GALABIN'S  Midwifery.  A  Manual  for  Students  and  Practitioners.  By  A.  Lewis 
Galabin,  m.d.,  f.r.c.p.,  Obstetric  Physician  to  Guy's  Hospital,  London,  and 
Professor  of  Midwifery  in  the  same  institution.     227  Illustrations. 

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GLISAN'S  Modern  Midwifery.  A  Text-book.  By  Rodney  Glisan,  m.d.,  Emeritus 
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Univ.,  Portland,  Oregon.     129  Illus.     8vo.     2d  Edition.  Cloth,  $3.00 


MEDICAL  AND  SCIENTIFIC  PUBLICA  TIONS. 11 

GARDNER'S  TECHNOLOGICAL  SERIES.    The  Brewer,  Distiller  and  Wine 

Manufacturer.     A  Handbook  for  all  Interested  in  the  Manufacture  and  Trade 
of  Alcohol  and  Its  Compounds.     Edited  by  John  Gardner,  f.c.s.     Illustrated. 

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Oils  and  Varnishes.    Edited  by  James  Cameron,  f.i.c.    Illustrated.     $2.50 

GIBBES'S  Practical  Histology  and  Pathology.    By  Heneage  Gibbes,  m.b.    i2mo. 

Third  Edition.  Cloth,  $1.75 

GILLIAM'S  Pathology.  The  Essentials  of  Pathology;  a  Handbook  for  Students. 
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Columbus,  O.    With  47  Illustrations.    i2mo.    '  Cloth,  $2.00 

GOODHART  and  STARR'S  Diseases  of  Children.  The  Student's  Guide  to  the 
Diseases  of  Children.  By  J.  F.  Goodhart,  m.d.,  f.r.c.p.,  Physician  to  Evelina 
Hospital  for  Children,  Demonstrator  of  Morbid  Anatomy  at  Guy's  Hospital. 
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GORGAS'S  Dental  Medicine.  A  Manual  of  Materia  Medica  and  Therapeutics. 
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Science,  Dental  Surgery  and  Dental  Mechanism  in  the  Dental  Department  of 
the  University  of  Maryland.     Second  Edition.     Enlarged.     8vo.        Cloth,  $3.25 

GOWERS,  Manual  of  Diseases  of  the  Nervous  System.  A  Complete  Text-book. 
By  William  R.  Gowers,  m.d.,  Prof.  Clinical  Medicine,  University  College, 
London.  Physician  to  National  Hospital  for  the  Paralyzed  and  Epileptic.  Com- 
prising over  400  Illustrations  and  1360  pages.     Octavo. 

Cloth,  $6.50;  Leather,  $7.50 

This  work  is  being  published  in  two  volumes  in  London.  By  special  arrange- 
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Spinal  Cord.  Diagnosis  of  Diseases  of  the  Spinal  Cord.  With  Colored  Plates 
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Ophthalmoscopy.  A  Manual  and  Atlas  of  Ophthalmoscopy.  With  16 
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Diagnosis  of  Diseases  of  the  Brain.    8vo.    Second  Edition.    Illustrated. 

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GROSS'S  Biography  of  John  Hunter.  John  Hunter  and  His  Pupils.  By  S.  D 
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GREENHOW.  Chronic  Bronchitis,  especially  as  connected  /vith  Gout,  Emphy- 
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GROVES  AND  THORP.  Chemical  Technology.  A  new  and  Complete  Work. 
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Vol.   I.     FUEL.     By   I->r.  V..).  Mills,  f.r.s.,  Professor  of  Chemistry  Anderson 
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Nearly  Ready. 


12  P.  BLAKISTON,  SON  &>  CO.'S 


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HABERSHON.  On  Some  Diseases  of  the  Liver.  By  S.  O.  Habershon,  m.d., 
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HADDON'S  Embryology.  An  Introduction  to  the 'Study  of  Embryology.  For 
the  Use  of  Students.  By  A.  C.  Haddon,  m.a.,  Prof,  of  Zoology,  Royal  College 
of  Science,  Dublin.     190  Illustrations.  Cloth,  6.00 

HALE.    On  the  Management  of  Children  in  Health  and  Disease.    A  Book  for 

Mothers.     By  Amie  M.  Hale,  m.d.     New  Enlarged  Edition.     i2mo.     Cloth,  .75 

HARE.     Tobacco,  Its  Physiological  and  Pathological  Effects.  Paper  Covers,  .50 

HARLAN.  Eyesight,  and  How  to  Care  for  It.  By  George  C.  Harlan,  m.d., 
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HARLEY.  Diseases  of  the  Liver,  With  or  Without  Jaundice.  Diagnosis  and 
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Illustrations.     8vo.  Price  reduced.     Cloth,  $3.00  ;  Leather,  $4.00 

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Harris,  m.d.,  d.d.s.,  late  President  of  the  Baltimore  Dental  College,  author  of 
"  Dictionary  of  Medical  Terminology  and  Dental  Surgery."  Eleventh  Edition. 
Revised  and  Edited  by  Ferdinand  J.  S.  Gorgas,  a.m.,  m.d.,  d.d.s.,  author  of 
"Dental  Medicine;"  Professor  of  the  Principles  of  Dental  Science,  Dental 
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Medical  and  Dental  Dictionary.    A  Dictionary  of  Medical  Terminology, 
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Dental  Surgery  in  the  Baltimore  College.    8vo.    Cloth,  $6.50  ;  Leather,  $7.50 
HARTRIDGE.    Refraction.     The  Refraction  of  the  Eye.     A  Manual  for  Students. 
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tholomew's Hospital ;  Ass't  Surgeon  to  the  Royal  Westminster  Ophthalmic  Hos- 
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HEATH'S  Operative  Surgery.  A  Course  of  Operative  Surgery,  consisting  of  a 
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Text  of  Each  Operation.  By  Christopher  Heath,  f.r.c.s.,  Holme  Professor 
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Revised.     Sold  by  Subscription.  Cloth,  $12.00 

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Practical  Anatomy.     A  Manual  of  Dissections.     Sixth  London  Edition.     24 
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16  P.  BLAKISTON,  SON  &*  CO.'S 


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SMITH  (TYLER).  Lectures  on  Obstetrics.  Delivered  at  St.  Mary's  Hospital. 
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SMYTHE'S  Medical  Heresies.  Historically  Considered.  A  Series  of  Critical  Es- 
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Sketch  and  Review  of  Homoeopathy,  Past  and  Present.  By  GONZALVO  C. 
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lege of  Physicians  and  Surgeons,  Indianapolis,  Indiana.      121110.         Cloth,  $1.25 

STAMMER.  Chemical  Problems,  with  Explanations  and  Answers.  By  Karl 
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STARR  and  WALKER.  Physiological  Action  of  Medicines.  Prepared  for  the 
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approval  of  the  Professor  of  Materia  Medica  (H.  C.  Wood,  m.d).  By  Louis 
Starr,  m.d.,  Clin.  Prof.  Dis.  of  Children,  in  the  Hospital  of  the  University,  and 
J.  B.Walker,  m.d.,  Prof,  of  Med.,  Woman's  Med'l  College  of  Phila.;  assisted 
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STEWART'S  Compend  of  Pharmacy.  Based  upon  "  Remington's  Text-Book  of 
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lino,  m.d.,  sc.d.,  Prof,  of  Phys.,  Owens  College,  Victoria  University,  Manchester. 
Examiner  in  Honor's  School  of  Science,  Oxford,  England.  142  Illustrations. 
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MEDICAL  AND  SCIENTIFIC  PUBLICATIONS^ 21 

STOCKEN'S  Dental  Materia  Medica.  Dental  Materia  Medica  and  Therapeutics, 
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SUTTON.  Pathology.  An  Introduction  to  General  Pathology,  founded  on  three 
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SWAIN.  Surgical  Emergencies,  together  with  the  Emergencies  Attendant  on 
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SWAYNE'S  Obstetric  Aphorisms,  for  the  Use  of  Students  commencing  Midwifery 
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